ALBERT

Description: Interest from the U.S. commercial aviation industry and commitments established by the U.S. Navy and Air Force to use renewable fuels has spurred interest in identifying and developing crops for renewable aviation fuel. Concern regarding greenhouse gas emissions associated with land-use change and shifting land grown for food to feedstock production for fuel has encouraged the concept of intensifying current prominent cropping systems through various double cropping strategies. Camelina ( Camelina sativa L.) and field pennycress ( Thlaspi arvense L.) are two winter oilseed crops that could potentially be integrated into the corn ( Zea mays L.)-soybean [( Glycine max (L.) Merr.] cropping system, which is the prominent cropping system in the U.S. Corn Belt. In addition to providing a feedstock for renewable aviation fuel production, integrating these crops into corn-soybean cropping systems could also potentially provide a range of ecosystem services. Some of these include soil protection from wind and water erosion, soil carbon sequestration, water quality improvement through nitrate reduction, and a food source for pollinators. However, integration of these crops into corn-soybean cropping systems also carries possible limitations, such as potential yield reductions of the subsequent soybean crop. This review identifies and discusses some of the key benefits and constraints of integrating camelina or field pennycress into corn-soybean cropping systems and identifies generalized areas for potential adoption in the U.S. Corn Belt. This article is protected by copyright. All rights reserved.

Description: Environmental or ‘ecological’ footprints have been widely used in recent years as indicators of resource consumption and waste absorption presented in terms of biologically productive land area [in global hectares (gha)] required per capita with prevailing technology. In contrast, ‘carbon footprints’ are the amount of carbon [or carbon dioxide equivalent] emissions for such activities in units of mass or weight (like kilograms per functional unit), but can be translated into a component of the environmental footprint (on a gha basis). The carbon and environmental footprints associated with the world production of liquid biofuels have been computed for the period 2010-2050. Estimates of future global biofuel production were adopted from the 2011 International Energy Agency (IEA) ‘technology roadmap’ for transport biofuels. This suggests that, although first generation biofuels will dominate the market up to 2020, advanced or second generation biofuels might constitute some 75% of biofuel production by 2050. The overall environmental footprint was estimated to be 0.29 billion (bn) gha in 2010, and is likely to grow to around 2.57 bn gha by 2050. It was then disaggregated into various components: bioproductive land, built land, carbon emissions, embodied energy, materials and waste, transport, and water consumption. This component-based approach has enabled the examination of the Manufactured and Natural Capital elements of the ‘four capitals’ model of sustainability quite broadly, along with specific issues (such as the linkages associated with the so-called ‘energy-land-water nexus’). Bioproductive land use was found to exhibit the largest footprint component (a 45% share in 2050), followed by the carbon footprint (23%), embodied energy (16%), and then the water footprint (14%). Footprint components related to built land, transport and waste arisings were all found to account for an insignificant proportion to the overall environmental footprint; together amounting to only about 2%. This article is protected by copyright. All rights reserved.

Description: Switchgrass-derived ethanol has been proposed as an alternative to fossil fuels to improve sustainability of the US energy sector. In the present study, life cycle analysis (LCA) was used to estimate the environmental benefits of this fuel. To better define the LCA environmental impacts associated with fertilization rates and farm-landscape topography, results from a controlled experiment were analyzed. Data from switchgrass plots planted in 2008, consistently managed with three nitrogen rates (0, 56 and 112 kg N ha −1 ), two landscape positions (shoulder and footslope), and harvested annually (starting from 3 rd year after planting) through 2014 were used as input into the Greenhouse gases, Regulated Emissions and Energy use in Transportation (GREET) model. Simulations determined nitrogen (N) rate and landscape impacts on the life cycle energy and emissions from switchgrass-ethanol used in a passenger car as ethanol-gasoline blends (10% ethanol:E10, 85% ethanol:E85s). Results indicated that E85s may lead to lower fossil fuels use (58 to 77%), greenhouse gas (GHG) emissions (33 to 82%), and particulate matter (PM2.5) emissions (15 to 54%) in comparison to gasoline. However, volatile organic compounds (VOCs) and other criteria pollutants such as nitrogen oxides (NOx), particulate matter (PM10), and sulfur dioxides (SO x ) were higher for E85s than those from gasoline. Nitrogen rate above 56 kg N ha −1 yielded no increased benefits; rather N rate increased (up to 2 fold) GHG, VOCs and criteria pollutants. Lower blend (E10) results were closely similar to those from gasoline. The landscape topography also influenced life cycle impacts. Biomass grown at the footslope of fertilized plots led to higher switchgrass biomass yield, lower GHG, VOCs and criteria pollutants in comparison to those at the shoulder position. Results also showed that replacing switchgrass before maximum stand life (10-20 yrs.) can further reduce the energy and emissions reduction benefits. This article is protected by copyright. All rights reserved.

Description: This paper evaluates the suitability of the ECOSSE model to estimate soil greenhouse gas fluxes from short rotation coppice willow (SRC-Willow), short rotation forestry (SRF-Scots Pine) and Miscanthus after land-use change from conventional systems (grassland and arable). We simulate heterotrophic respiration (R h ), nitrous oxide (N 2 O) and methane (CH 4 ) fluxes at four paired sites in the UK, and compare them to estimates of R h derived from the ecosystem respiration estimated from eddy covariance (EC) and R h estimated from chamber (IRGA) measurements, as well as direct measurements of N 2 O and CH 4 fluxes. Significant association between modelled and EC-derived R h was found under Miscanthus , with correlation coefficient ( r ) ranging between 0.54 and 0.70. Association between IRGA-derived R h and modelled outputs was statistically significant at the Aberystwyth site ( r = 0.64) but not significant at the Lincolnshire site ( r = 0.29). At all SRC-Willow sites, significant association was found between modelled and measurement-derived R h (0.44 ≤ r ≤ 0.77); significant error was found only for the EC-derived R h at the Lincolnshire site. Significant association and no significant error were also found for SRF-Scots Pine and perennial grass. For the arable fields, the modelled CO 2 correlated well just with the IRGA-derived R h at one site ( r = 0.75). No bias in the model was found at any site, regardless of the measurement type used for the model evaluation. Across all land-uses, fluxes of CH 4 and N 2 O were shown to represent a small proportion of the total greenhouse gas balance; these fluxes have been modelled adequately on a monthly time-step. This study provides confidence in using ECOSSE for predicting the impacts of future land-use on greenhouse gas balance, at site level as well as at national level. This article is protected by copyright. All rights reserved.

Description: A primary goal of many next-generation bioenergy systems is to increase ecosystem services such as soil carbon (C) storage and nutrient retention. Evaluating whether bioenergy management systems are achieving these goals is challenging in part because these processes occur over long periods of time at varying spatial scales. Investigation of microbially mediated soil processes at the microbe scale may provide early insights into the mechanisms driving these long-term ecosystem services. Furthermore, seasonal fluctuations in microbial activity are rarely considered when estimating whole ecosystem functioning, but are central to decomposition, soil structure, and realized C storage. Some studies have characterized extracellular enzyme activity within soil structures (aggregates); however, seasonal variation in decomposition at the microscale remains virtually unknown, particularly in managed ecosystems. As such, we hypothesize that temporal variation in aggregate turnover is a strong regulator of microbial activity, with important implications for decomposition and C and nitrogen (N) storage in bioenergy systems. We address variation in soil microbial extracellular enzyme activity spatially across soil aggregates and temporally across two growing seasons in three ecosystems managed for bioenergy feedstock production: Zea mays L. (corn) agroecosystem, fertilized and unfertilized reconstructed tallgrass prairie. We measured potential N-acetyl-glucosaminidase (NAG), β-glucosidase (BG), β-xylosidase (BX), and cellobiohydrolase (CB) enzyme activity. Aggregate turnover in prairie systems was driven by precipitation events and seasonal spikes in enzyme activity corresponded with aggregate turnover events. In corn monocultures, soil aggregates turned over early in the growing season, followed by increasing, albeit low, enzyme activity throughout the growing season. Independent of management system or sampling date, NAG activity was greatest in large macroaggregates (〉2000  μ m) and CB activity was greatest in microaggregates (〈250  μ m). High microbial activity coupled with greater aggregation in prairie bioenergy systems may reduce loss of soil organic matter through decomposition and increase soil C storage.

Description: This paper provides spatial estimates of potentially available biomass for bioenergy in Australia in 2010, 2030 and 2050 (under clearly stated assumptions) for the following biomass sources: crop stubble, native grasses, pulpwood and residues (created either during forest harvesting or wood processing) from plantations and native forests, bagasse, organic municipal solid waste, and new short rotation tree crops. For each biomass type we estimated annual potential availability at the finest scale possible with readily accessible data, and then aggregated to make estimates for each of 60 Statistical Divisions (administrative areas) across Australia. The potentially available lignocellulosic biomass is estimated at approximately 80 Mt per year, with the major contributors of crop stubble (27.7 Mt per year), grasses (19.7 Mt per year) and forest plantations (10.9 Mt per year). Over the next 20–40 years, total potentially available biomass could increase to 100–115 Mt per year, with new plantings of short-rotation trees being the major source of the increase (14.7 Mt per year by 2030 and 29.3 Mt per year by 2050). We exclude oilseeds, algae and ‘regrowth’ i.e. woody vegetation naturally regenerating on previously cleared land, which may be important in several regions of Australia (Booth et al ., 2014, Hayward et al ., 2014). We briefly discuss some of the challenges to providing a reliable and sustainable supply of the large amounts of biomass required to build a bioenergy industry of significant scale. More detailed regional analyses, including of the costs of delivered biomass, logistics and economics of harvest, transport and storage, competing markets for biomass, and a full assessment of the sustainability of production are needed to underpin investment in specific conversion facilities (e.g. Rodriguez et al ., 2011a). This article is protected by copyright. All rights reserved.

Description: Bioenergy crop cultivation on former peat extraction areas is a potential after-use option that provides a source of renewable energy while mitigating climate change through enhanced carbon (C) sequestration. This study investigated the full C and greenhouse gas (GHG) balances of fertilized (RCG-F) and non-fertilized (RCG-C) reed canary grass (RCG; Phalaris arundinacea ) cultivation compared to bare peat (BP) soil within an abandoned peat extraction area in western Estonia during a dry year. Vegetation sampling, static chamber and lysimeter measurements were carried out to estimate above- and belowground biomass production and allocation, fluxes of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) in cultivated strips and drainage ditches as well as the dissolved organic carbon (DOC) export, respectively. Heterotrophic respiration was determined from vegetation-free trenched plots. Fertilization increased the above- to belowground biomass production ratio and the autotrophic to heterotrophic respiration ratio. The full C balance (incl. CO 2 , CH 4 and DOC fluxes from strips and ditches) was 96, 215 and 180 g C m −2 yr −1 in RCG-F, RCG-C and BP, respectively, suggesting that all treatments acted as C sources during the dry year. The C balance was driven by variations in the net CO 2 exchange, whereas the combined contribution of CH 4 and DOC fluxes was 〈 5%. The GHG balances were 3.6, 7.9 and 6.6 t CO 2 eq ha −1 yr −1 in RCG-F, RCG-C and BP, respectively. The CO 2 exchange was also the dominant component of the GHG balance while the contributions of CH 4 and N 2 O were 〈 1% and 1-6%, respectively. Overall, this study suggests that maximizing plant growth and the associated CO 2 uptake through adequate water and nutrient supply is a key prerequisite for ensuring sustainable high yields and climate benefits in RCG cultivations established on organic soils following drainage and peat extraction. This article is protected by copyright. All rights reserved.

Description: This study models and quantifies spatially-referenced probability distributions of corn residue cost and assesses their influence on comparative advantages of different areas of the Corn Belt to attract biofuel plants. Results suggest that irrigated areas of the Corn Belt, despite their relatively low planting density, may result more attractive than some of their rainfed counterparts in the eastern Corn Belt due to low risk in feedstock cost resulting from stability of yields. Therefore agricultural districts in the Great Plains of the US may not need to pay high subsidies to compete with those in the eastern Corn Belt to attract biofuel firms. Policy restrictions on irrigation due to concerns over groundwater depletion may, however, diminish the relative comparative advantage of the irrigated Corn Belt for biofuel production. This article is protected by copyright. All rights reserved.

Description: Willow species ( Salix ) are important as short rotation biomass crops for bioenergy, which creates a demand for faster genetic improvement and breeding through deployment of molecular marker assisted selection (MAS). In order to find markers associated with important adaptive traits, such as growth and phenology, for use in MAS, we genetically dissected the trait variation of a Salix viminalis (L.) population of 323 accessions. The accessions were sampled throughout northern Europe and were established at two field sites in Pustnäs, Sweden and at Woburn, UK, offering the opportunity to assess the impact of genotype-by-environment interactions (G×E) on trait-marker associations. Field measurements were recorded for growth and phenology traits. The accessions were genotyped using 1536 SNP markers developed from phenology candidate genes and from genes previously observed to be differentially expressed in contrasting environments. Association mapping between 1233 of these SNPs and the measured traits was performed taking into account population structure and threshold selection bias. At a false discovery rate (FDR) of 0.2, 29 SNPs were associated with bud burst, leaf senescence, number of shoots or shoot diameter. The percentage of accession variation () explained by these associations ranged from 0.3% to 4.4%, suggesting that the studied traits are controlled by many loci of limited individual impact. Despite this, a SNP in the EARLY FLOWERING 3 gene was repeatedly associated (FDR〈0.2) with bud burst. The rare homozygous genotype exhibited 0.4 – 1.0 lower bud burst scores than the other genotype classes on a five grade scale. Consequently this marker could be promising for use in MAS and the gene deserves further study. Otherwise, associations were less consistent across sites, likely due to their small -estimates and to considerable G×E-interactions indicated by multivariate association analyses and modest trait accession correlations across sites (0.32–0.61). This article is protected by copyright. All rights reserved.

Description: Woody biomass from the southeast United States is expected to play an important role in meeting European Union renewable energy targets. In crafting policies to guide bioenergy development and in guiding investment decisions to meet established policy goals, a firm understanding of the interaction between policy targets and forest biomass markets is necessary, as is the effect that this interaction will have on environmental and economic objectives. This analysis increases our understanding of these interactions by modeling the response of southern US forest markets to new pellet demand in the presence of sustainability sourcing or harvest criteria. We first assess the influence of EU recommended sustainability guidelines on the forest inventory available to supply EU markets, and then model changes in forest composition and extent in response to expected increases in pellet demand. Next, we assess how sustainability guidelines can influence the evolution of forest markets in the region, paying particular attention to changes in land use and forest carbon. Regardless of whether sustainability guidelines are applied, we find increased removals, an increase in forest area, and little change in forest inventory. We also find annual gains in forest carbon in most years of the analysis. The incremental effect of sustainability guideline application on forest carbon and pellet greenhouse gas (GHG) balance is difficult to discern, but results suggest that guidelines could be steering production away from sensitive forest types inherently less responsive to changing market conditions. Pellet GHG balance shows significant annual change and is attributable to the complexity of the underlying forest landscape. The manner by which GHG balance is tracked is thus a critical policy decision, reinforcing the importance and relevance of current efforts to develop approaches to accurately account for the GHG implications of biomass use both in the United States and European Union.

Description: In commercially grown Miscanthus x giganteus , despite imposing a yield penalty, post-winter harvests improve quality criteria for thermal conversion and crop sustainability through remobilisation of nutrients to the underground rhizome. We examined 16 Miscanthus genotypes with different flowering and senescence times for variation in N, P, K, moisture, ash, Cl, and Si contents, hypothesising that early flowering and senescence could result in improved biomass quality and/or enable an earlier harvest of biomass, i.e. in autumn at peak yield. Ideal crop characteristics at harvest are low N and P to reduce future fertiliser inputs, low K and Cl to reduce corrosion in boilers, low moisture to reduce spoilage and transportation costs, and low Si and ash to reduce slagging and consequent operational downtime. Stems and leaves were harvested during: summer, autumn, and the following spring after overwinter ripening. In spring, stem contents of N were 30 to 60 mg kg -1 , P were 203-1132 mg kg -1 , K were 290-4098 mg kg -1 , Cl were 10 to 23 mg kg -1 , and moisture were 12-38%. Notably, late senescence resulted in increased N, P, K, Cl, moisture and ash contents, and should therefore be avoided for thermochemical conversion. Flowering and senescence led to overall improved combustion quality, where flowered genotypes tended towards lower P, K, Cl, and moisture contents; marginally less, or similar, N, Si and ash contents; and a similar HHV, compared to those that had not flowered. Such genotypes could potentially be harvested in the autumn. However, one genotype that did not flower in our trial exhibited sufficiently low N and K content in autumn to meet the EN plus wood pellet standards for those traits, and some of the lowest P, moisture and ash contents in our trial and is thus a target for future research and breeding. This article is protected by copyright. All rights reserved.

Description: The implementation of measures to increase productivity and resource efficiency in food and bioenergy chains as well as to more sustainably manage land use can significantly increase the biofuel production potential while limiting the risk of causing ILUC. However, the application of these measures may influence the GHG balance and other environmental impacts of agricultural and biofuel production. This study applies a novel, integrated approach to assess the environmental impacts of agricultural and biofuel production for three ILUC mitigation scenarios, representing a low, medium and high miscanthus-based ethanol production potential, and for three agricultural intensification pathways in terms of sustainability in Lublin province in 2020. Generally, the ILUC mitigation scenarios attain lower net annual emissions compared to a baseline scenario that excludes ILUC mitigation and bioethanol production. However, the reduction potential significantly depends on the intensification pathway considered. For example, in the moderate ILUC mitigation scenario, the net annual GHG emissions in the case study are 2.3 MtCO 2 -eq yr −1 (1.8 tCO 2 -eq ha −1 yr −1 ) for conventional intensification and -0.8 MtCO 2 -eq yr −1 (-0.6 tCO 2 -eq ha −1 yr −1 ) for sustainable intensification, compared to 3.0 MtCO 2 -eq yr −1 (2.3 tCO 2 -eq ha −1 yr −1 ) in the baseline scenario. In addition, the intensification pathway is found to be more influential for the GHG balance than the ILUC mitigation scenario, indicating the importance of how agricultural intensification is implemented in practice. Furthermore, when the net emissions are included in the assessment of GHG emissions from bioenergy, the ILUC mitigation scenarios often abate GHG emissions compared to gasoline. But sustainable intensification is required to attain GHG abatement potentials of 90% or higher. A qualitative assessment of the impacts on biodiversity, water quantity and quality, soil quality and air quality also emphasizes the importance of sustainable intensification. This article is protected by copyright. All rights reserved.

Description: We estimate the mitigation potential of local use of bioenergy from harvest residues for the 2.3 × 10 6  km 2 (232 Mha) of Canada's managed forests from 2017 to 2050 using three models: Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3), a harvested wood products (HWP) model that estimates bioenergy emissions, and a model of emission substitution benefits from the use of bioenergy. We compare the use of harvest residues for local heat and electricity production relative to a base case scenario and estimate the climate change mitigation potential at the forest management unit level. Results demonstrate large differences between and within provinces and territories across Canada. We identify regions with increasing benefits to the atmosphere for many decades into the future and regions where no net benefit would occur over the 33-year study horizon. The cumulative mitigation potential for regions with positive mitigation was predicted to be 429 Tg CO 2 e in 2050, with 7.1 TgC yr  −1 of harvest residues producing bioenergy that met 3.1% of the heat demand and 2.9% of the electricity demand for 32.1 million people living within these regions. Our results show that regions with positive mitigation produced bioenergy, mainly from combined heat and power facilities, with emissions intensities that ranged from roughly 90 to 500 kg CO 2 e MWh −1 . Roughly 40% of the total captured harvest residue was associated with regions that were predicted to have a negative cumulative mitigation potential in 2050 of −152 Tg CO 2 e. We conclude that the capture of harvest residues to produce local bioenergy can reduce GHG emissions in populated regions where bioenergy, mainly from combined heat and power facilities, offsets fossil fuel sources (fuel oil, coal and petcoke, and natural gas).

Description: National governments and international organisations perceive bioenergy, from crops such as Miscanthus , to have an important role in mitigating greenhouse gas (GHG) emissions and combating climate change. In this research we address three objectives aimed at reducing uncertainty regarding the climate change mitigation potential of commercial Miscanthus plantations in the UK: i) to examine soil temperature and moisture as potential drivers of soil GHG emissions through four years of parallel measurements, ii) to quantify carbon (C) dynamics associated with soil sequestration using regular measurements of topsoil (0-30 cm) C and the surface litter layer, and iii) to calculate a life-cycle GHG budget using site-specific measurements, enabling the GHG intensity of Miscanthus used for electricity generation to be compared against coal and natural gas. Our results show that methane (CH 4 ) and nitrous oxide (N 2 O) emissions contributed little to the overall GHG budget of Miscanthus , while soil respiration offset 30% of the crop's net aboveground C uptake. Temperature sensitivity of soil respiration was highest during crop growth and lowest during winter months. We observed no significant change in topsoil C or nitrogen stocks following 7 years of Miscanthus cultivation. The depth of litter did, however, increase significantly, stabilising at approximately 7 tonnes dry biomass per hectare after 6 years. The cradle-to-farm gate GHG budget of this crop indicated a net removal of 24.5 t CO 2 -eq ha −1 yr −1 from the atmosphere despite no detectable C sequestration in soils. When scaled up to consider the full life-cycle, Miscanthus fared very well in comparison to coal and natural gas, suggesting considerable CO 2 offsetting per kWh generated. Although the comparison does not account for the land area requirements of the energy generated, Miscanthus used for electricity generation can make a significant contribution to climate change mitigation even when combusted in conventional steam turbine power plants. This article is protected by copyright. All rights reserved.

Description: Domestic and foreign renewable energy targets and financial incentives have increased demand for woody biomass and bioenergy in the southeastern United States. This demand is expected to be met through purpose-grown agricultural bioenergy crops, short-rotation tree plantations, thinning and harvest of planted and natural forests, and forest harvest residues. With results from a forest economics model, spatially explicit state-and-transition simulation models, and species–habitat models, we projected change in habitat amount for 16 wildlife species caused by meeting a renewable fuel target and expected demand for wood pellets in North Carolina, USA. We projected changes over 40 years under a baseline ‘business-as-usual’ scenario without bioenergy production and five scenarios with unique feedstock portfolios. Bioenergy demand had potential to influence trends in habitat availability for some species in our study area. We found variation in impacts among species, and no scenario was the ‘best’ or ‘worst’ across all species. Our models projected that shrub-associated species would gain habitat under some scenarios because of increases in the amount of regenerating forests on the landscape, while species restricted to mature forests would lose habitat. Some forest species could also lose habitat from the conversion of forests on marginal soils to purpose-grown feedstocks. The conversion of agricultural lands on marginal soils to purpose-grown feedstocks increased habitat losses for one species with strong associations with pasture, which is being lost to urbanization in our study region. Our results indicate that landscape-scale impacts on wildlife habitat will vary among species and depend upon the bioenergy feedstock portfolio. Therefore, decisions about bioenergy and wildlife will likely involve trade-offs among wildlife species, and the choice of focal species is likely to affect the results of landscape-scale assessments. We offer general principals to consider when crafting lists of focal species for bioenergy impact assessments at the landscape scale.

Description: Production of woody biomass for bioenergy, whether wood pellets or liquid biofuels, has the potential to cause substantial landscape change and concomitant effects on forest ecosystems, but the landscape effects of alternative production scenarios have not been fully assessed. We simulated landscape change from 2010 to 2050 under five scenarios of woody biomass production for wood pellets and liquid biofuels in North Carolina, in the southeastern United States, a region that is a substantial producer of wood biomass for bioenergy and contains high biodiversity. Modeled scenarios varied biomass feedstocks, incorporating harvest of ‘conventional’ forests, which include naturally regenerating as well as planted forests that exist on the landscape even without bioenergy production, as well as purpose-grown woody crops grown on marginal lands. Results reveal trade-offs among scenarios in terms of overall forest area and the characteristics of the remaining forest in 2050. Meeting demand for biomass from conventional forests resulted in more total forest land compared with a baseline, business-as-usual scenario. However, the remaining forest was composed of more intensively managed forest and less of the bottomland hardwood and longleaf pine habitats that support biodiversity. Converting marginal forest to purpose-grown crops reduced forest area, but the remaining forest contained more of the critical habitats for biodiversity. Conversion of marginal agricultural lands to purpose-grown crops resulted in smaller differences from the baseline scenario in terms of forest area and the characteristics of remaining forest habitats. Each scenario affected the dominant type of land-use change in some regions, especially in the coastal plain that harbors high levels of biodiversity. Our results demonstrate the complex landscape effects of alternative bioenergy scenarios, highlight that the regions most likely to be affected by bioenergy production are also critical for biodiversity, and point to the challenges associated with evaluating bioenergy sustainability.

Description: Growing cellulosic feedstock crops (e.g., switchgrass) for biofuel is more environmentally sustainable than corn-based ethanol. Specifically, this practice can reduce soil erosion and water quality impairment from pesticides and fertilizer, improve ecosystem services and sustainability (e.g., serve as carbon sinks), and minimize impacts on global food supplies. The main goal of this study is to identify high risk marginal croplands that are potentially suitable for growing cellulosic feedstock crops (e.g., switchgrass) in the U.S. Great Plains (GP). Satellite-derived growing season Normalized Difference Vegetation Index, a switchgrass biomass productivity map obtained from a previous study, U.S. Geological Survey (USGS) irrigation and crop masks, and U.S. Department of Agriculture (USDA) crop indemnity maps for the GP were used in this study. Our hypothesis was that croplands with relatively low crop yield but high productivity potential for switchgrass may be suitable for converting to switchgrass. Areas with relatively low crop indemnity (crop indemnity 〈 $2,157,068) were excluded from the suitable areas based on low probability of crop failures. Results show that approximately 650,000 ha of marginal croplands in the GP are potentially suitable for switchgrass development. The total estimated switchgrass biomass productivity gain from these suitable areas is about 5.9 million metric tons. Switchgrass can be cultivated in either lowland or upland regions in the GP depending on the local soil and environmental conditions. This study improves our understanding of ecosystem services and the sustainability of cropland systems in the GP. Results from this study provide useful information to land managers for making informed decisions regarding switchgrass development in the GP. This article is protected by copyright. All rights reserved.

Description: The application of biochar as a soil amendment to improve soil fertility has been suggested as a tool to reduce soil-borne CO 2 and non-CO 2 greenhouse gas emissions, especially nitrous oxide (N 2 O). Both lab and field trials have demonstrated N 2 O emission reduction by biochar amendment, but the long-term effect (〉1 year) has been questioned. Here we present results of a combined microcosm and field study using a powdered beech wood biochar from slow pyrolysis. The field experiment showed that both CO 2 and N 2 O emissions were still effectively reduced by biochar in the third year after application. However, biochar did not influence the biomass yield of sunflower for biogas production ( Helianthus annuus L.). Biochar reduced bulk density and increased soil aeration and thus reduced the water filled pore space (WFPS) in the field, but was also able to suppress N 2 O emission in the microcosms experiment conducted at constant WFPS. For both experiments, biochar had limited impact on soil mineral nitrogen speciation, but it reduced the accumulation of nitrite in the microcosms. Extraction of soil DNA and quantification of functional marker genes by qPCR showed that biochar did not alter the abundance of nitrogen-transforming bacteria and archaea in both field and microcosm experiments. In contradiction to previous experiments, this study demonstrates the long-term N 2 O emission suppression potential of a wood biochar and thus highlights its overall climate change mitigation potential. While a detailed understanding of the underlying mechanisms requires further research we provide evidence for a range of biochar-induced changes to the soil environment and their change with time that might explain the often observed N 2 O emission suppression. This article is protected by copyright. All rights reserved.

Description: Simulation models for perennial energy crops such as switchgrass ( Panicum virgatum L.) and Miscanthus ( Miscanthus x giganteus ) can be useful tools to design management strategies for biomass productivity improvement in US environments. The Agricultural Production Systems Simulator (APSIM) is a biophysical model with the potential to simulate the growth of perennial crops. APSIM crop modules do not exist for switchgrass and Miscanthus, however, re-parameterization of existing APSIM modules could be used to simulate the growth of these perennials. Our aim was to evaluate the ability of APSIM to predict the dry matter (DM) yield of switchgrass and Miscanthus at several US locations. The Lucerne (for switchgrass) and Sugarcane (for Miscanthus ) APSIM modules were calibrated using data from four locations in Indiana. A sensitivity analysis informed the relative impact of changes in plant and soil parameters of APSIM Lucerne and APSIM Sugarcane modules. An independent dataset of switchgrass and Miscanthus DM yields from several US environments was used to validate these re-parameterized APSIM modules. The re-parameterized modules simulated DM yields of switchgrass (0.95 for CCC [concordance correlation coefficient] and 0 for SB [bias of the simulation from the measurement]) and Miscanthus (0.65 and 0% for CCC and SB, respectively) accurately at most locations with the exception of switchgrass at southern US sites (0.01 for CCC and 2% for SB). Therefore, the APSIM model is a promising tool for simulating DM yields for switchgrass and Miscanthus while accounting for environmental variability. Given our study was strictly based on APSIM calibrations at Indiana locations, additional research using more extensive calibration data may enhance APSIM robustness. This article is protected by copyright. All rights reserved.

Description: The goal of this research is to determine the changes in streamflow, dissolved inorganic nitrogen (DIN) leaching and export to the Gulf of Mexico associated with a range of large-scale dedicated perennial cellulosic bioenergy production scenarios within in the Mississippi-Atchafalaya River Basin (MARB). To achieve this goal, we used Agro-IBIS, a vegetation model capable of simulating the biogeochemistry of row crops, miscanthus and switchgrass, coupled with THMB, a hydrology model capable of simulating streamflow and DIN export. Simulations were conducted at varying fertilizer application rates (0 to 200 kg N ha −1 ) and fractional replacement (5 to 25%) of current row crops with miscanthus or switchgrass across the MARB. The analysis also includes two scenarios where miscanthus and switchgrass (MRX and MRS respectively) each replace the ca. 40% of maize production currently devoted to ethanol. Across the scenarios, there were minor reductions in runoff and streamflow throughout the MARB, with the largest differences (ca. 6%) occurring for miscanthus at the highest fractional replacement scenarios in drier portions of the region. However, differences in total MARB discharge at the basin outlet were less than 1.5% even in the MRX scenario. Reductions in DIN export were much larger on a percentage basis than reductions in runoff, with the highest replacement scenarios decreasing long-term mean DIN export by ca. 15 and 20% for switchgrass and miscanthus, respectively. Fertilization scenarios show that significant reductions in DIN leaching are possible even with application rates of 100 and 150 kg N ha −1 for switchgrass and miscanthus respectively. These results indicate that, given targeted management strategies, there is potential for miscanthus and switchgrass to provide key ecosystem services by reducing the export of DIN, while avoiding hydrologic impacts of reduced streamflow. This article is protected by copyright. All rights reserved.

Description: Conversion of large areas of agricultural grassland is inevitable if European and UK domestic production of biomass is to play a significant role in meeting demand. Understanding the impact of these land-use changes on soil carbon cycling and stocks depends on accurate predictions from well parameterised models. Key considerations are cultivation disturbance and the effect of autotrophic root input stimulation on soil carbon decomposition under novel biomass crops. This paper presents partitioned parameters from the conversion of semi-improved grassland to Miscanthus bioenergy production and compares the contribution of autotrophic and heterotrophic respiration to overall ecosystem respiration of CO 2 in the first and second years of establishment. Repeated measures of respiration from within and without root exclusion collars were used to produce time series model integrations separating live root inputs from decomposition of grass residues ploughed in with cultivation of the new crop. These parameters were then compared to total ecosystem respiration derived from eddy covariance sensors. Average soil surface respiration was 13.4% higher in the second growing season, increasing from 2.9 to 3.29 g CO 2 -C m -2 day -1 . Total ecosystem respiration followed a similar trend, increasing from 4.07 to 5.4 g CO 2 -C m -2 day -1 . Heterotrophic respiration from the root exclusion collars was 32.2% lower in the second growing season at 1.20 g CO 2 -C m -2 day -1 compared to the previous year at 1.77 g CO 2 -C m -2 day -1 . Of the total respiration flux over the two year time period, above ground autotrophic respiration plus litter decomposition contributed 38.46% to total ecosystem respiration while below ground autotrophic respiration and stimulation by live root inputs contributed 46.44% to soil surface respiration. This figure is notably higher than mean figures for non-forest soils derived from the literature and demonstrates the importance of crop specific parameterisation of respiration models. This article is protected by copyright. All rights reserved.

Description: Intercropping switchgrass ( Panicum virgatum L.) with loblolly pine ( Pinus taeda L.) has been proposed for producing bioenergy feedstock in the southeastern United States. This study investigated switchgrass growth and pine-switchgrass interactions at two established experimental fields (7-yr old Lenoir site and 5-yr old Carteret site) located on the coastal plain of Eastern United States. Position effects (edge and center of switchgrass alley in intercropping plots) and treatment effects (intercropping vs. grass only) on aboveground switchgrass growth were evaluated. Interspecific interactions with respect to capturing resources (light, soil water and nitrogen) were investigated by measuring photosynthetically active radiation (PAR) above grass canopy, soil moisture, and soil mineral nitrogen contents. Switchgrass growth was significantly (p=0.001) affected by treatments in Lenoir and by position (p〈0.0001) in both study sites. Relative to the center, PAR above grass canopy at edge in both sites was about 48% less during the growing season. Soil water content during the growing season at the edge was significantly (p=0.0001) lower by 23% than at center in Lenoir, while no significant (p=0.42) difference was observed in Carteret, in spite of more grass growth at center at both sites. Soil mineral nitrogen content at center of intercropping plots in Lenoir (no fertilization during 2015) was significantly (p〈0.07) lower than at edge during the peak of growing season (June, July, and August), but not during early- and late parts of growing season (May, September, and November). Position effects on soil water and mineral nitrogen were less evident under conditions with higher external inputs (rainfall and fertilization) and lower plant uptake during non-growing seasons. Results from this study contributed to a better understanding of above- and belowground pine-switchgrass interactions which is necessary to properly manage this new cultivation system for bioenergy production in the southeastern United States. This article is protected by copyright. All rights reserved.

Description: Miscanthus has a high potential as a biomass feedstock for biofuel production. Drought tolerance is an important breeding goal in miscanthus as water deficit is a common abiotic stress and crop irrigation is in most cases uneconomical. Drought may not only severely reduce biomass yields, but also affect biomass quality for biofuel production as cell wall remodeling is a common plant response to abiotic stresses. The quality and plant weight of 50 diverse miscanthus genotypes were evaluated under control and drought conditions (28 days no water) in a greenhouse experiment. Overall, drought treatment decreased plant weight by 45%. Drought tolerance – as defined by maintenance of plant weight - varied extensively among the tested miscanthus genotypes and ranged from 30 to 110%. Biomass composition was drastically altered due to drought stress, with large reductions in cell wall and cellulose content and a substantial increase in hemicellulosic polysaccharides. Stress had only a small effect on lignin content. Cell wall structural rigidity was also affected by drought conditions; substantially higher cellulose conversion rates were observed upon enzymatic saccharification of drought-treated samples with respect to controls. Both cell wall composition and the extent of cell wall plasticity under drought varied extensively among all genotypes, but only weak correlations were found with the level of drought tolerance, suggesting their independent genetic control. High drought tolerance and biomass quality can thus potentially be advanced simultaneously. The extensive genotypic variation found for most traits in the evaluated miscanthus germplasm provides ample scope for breeding of drought-tolerant varieties that are able to produce substantial yields of high quality biomass under water deficit conditions. The higher degradability of drought-treated samples makes miscanthus an interesting crop for the production of second generation biofuels in marginal soils. This article is protected by copyright. All rights reserved.

Description: Uncertainty in soil carbon (C) fluxes across different land-use transitions is an issue that needs to be addressed for the further deployment of perennial bioenergy crops. A large-scale short-rotation coppice (SRC) site with poplar ( Populus ) and willow ( Salix ) was established to examine the land-use transitions of arable and pasture to bioenergy. Soil C pools, output fluxes of soil CO 2 , CH 4 , dissolved organic carbon (DOC) and volatile organic compounds, as well as input fluxes from litter fall and from roots were measured over a four-year period, along with environmental parameters. Three approaches were used to estimate changes in the soil C. The largest C pool in the soil was the soil organic carbon (SOC) pool, and increased after four years of SRC from 10.9 to 13.9 kg C m -2 . The belowground woody biomass (coarse roots) represented the second largest C pool, followed by the fine roots (Fr). The annual leaf fall represented the largest C input to the soil, followed by weeds and Fr. After the first harvest we observed a very large C input into the soil from high Fr mortality. The weed inputs decreased as trees grew older and bigger. Soil respiration averaged 568.9 g C m -2 y -1 . Leaching of DOC increased over the three years from 7.9 to 14.5 g C m -2 . The pool-based approach indicated an increase of 3360 g C m -2 in the SOC pool over the four-year period, which was high when compared with the -27 g C m -2 estimated by the flux-based approach and the -956 g C m -2 of the combined eddy-covariance+biometric approach. High uncertainties were associated to the pool-based approach. Our results suggest using the C flux approach for assessment of the short/medium-term SOC balance at our site, while SOC pool changes can only be used for long-term C balance assessments. This article is protected by copyright. All rights reserved.

Description: Current quantification of Climate Warming Mitigation Potential (CWMP) of biomass-derived energy has focused primarily on its biogeochemical effects. This study used site-level observations of carbon, water, and energy fluxes of biofuel crops to parameterize and evaluate the Community Land Model (CLM) and estimate CO 2 fluxes, surface energy balance, soil carbon dynamics of corn ( Zea mays ), switchgrass ( Panicum virgatum ) and miscanthus ( Miscanthus × giganteus ) ecosystems across the conterminous United States considering different agricultural management practices and land-use scenarios. We find that neglecting biophysical effects underestimates the CWMP of transitioning from croplands and marginal lands to energy crops. Biogeochemical effects alone result in changes in carbon storage of -1.9, 49.1 and 69.3 g C m −2 y −1 compared to 20.5, 78.5 and 96.2 g C m −2 y −1 when considering both biophysical and biogeochemical effects for corn, switchgrass and miscanthus, respectively. The biophysical contribution to CWMP is dominated by changes in latent heat fluxes. Using the model to optimize growth conditions through fertilization and irrigation increases the CWMP further to 79.6, 98.3 and 118.8 g C m −2 y −1 , respectively, representing the upper threshold for CWMP. Results also show that the CWMP over marginal lands is lower than that over croplands. This study highlights that neglecting the biophysical effects of altered surface energy and water balance underestimates the CWMP of transitioning to bioenergy crops at regional scales. This article is protected by copyright. All rights reserved.

Description: Wide scale application of biochar to soil has been suggested as a mechanism to offset increases in CO 2 emissions through the long-term sequestration of a carbon rich and inert substance to the soil, but the implications of this for soil diversity and function remain to be determined. Biochar is capable of inducing changes in soil bacterial communities, but the exact impacts of its application are poorly understood. Using three European sites (UK SRC, short rotation coppice, French grassland (FR) and Italian SRF, short rotation forestry (IT)) treated with identical biochar applications; we undertook 16S and ITS amplicon DNA sequencing. In addition, we carried out assessments of community change over time and N and P mobilisation in the UK. Significant changes in bacterial and community structure occurred due to treatment, although the nature of the changes varied by site. STAMP differential abundance analysis showed enrichment of Gemmatimonadete and Acidobacteria in UK biochar plots one year after application, whilst control plots exhibited enriched Gemmataceae, Isosphaeraceae and Koribacteraceae . Increased mobility of ammonium and phosphates were also detected after one year, coupled with a shift from acid to alkaline phophomonoesterase activity, which may suggest an ecological and functional shift towards a more copiotrophic ecology. Italy also exhibited enrichments, in both the Proteobacteria (driven by an increase in the order Rhizobiales ) and the Gemmatimonadetes . No significant change in the abundance of individual taxa were noted in FR, although a small significant change in unweighted UNIFRAC occurred, indicating variation in the identities of taxa present due to treatment. Fungal β diversity was affected by treatment in IT and FR, but was unaffected in UK samples. The effects of time and site were greater than that of biochar application in UK samples. Overall, this report gives a tantalising view of the soil microbiome at several sites across Europe, and suggests that although application of biochar has significant effects on microbial communities, these may be small compared with the highly variable soil microbiome that is found in different soils and changes with time. This article is protected by copyright. All rights reserved.

Description: The cost of supplying wood biomass from forestry operations in remote areas has been an obstacle to expansion of forest-based bioenergy in much of the western United States. Economies of scale in the production of liquid fuels from lignocellulosic biomass feedstocks favor large centralized biorefineries. Increasing transportation efficiency through torrefaction and pelletization at distributed satellite facilities may serve as a means to expand the utilization of forestry residuals in biofuels production. To investigate this potential, a mixed-integer linear program was developed to optimize the feedstock supply chain design with and without distributed pretreatment. The model uses techno-economic assessment of scale-dependent biomass pretreatment processes from existing literature and multi-modal biomass transportation cost evaluations derived from a spatially explicit network analysis as input. In addition, the sensitivity of the optimal system configuration was determined for variations of key input parameters including the production scale of pretreatment facilities, road and rail transportation costs, and feedstock procurement costs. Torrefaction and densification were found to reduce transportation costs by $0.84/GJ and overall delivered costs by $0.24/GJ, representing 14.5% and 5.2% cost reductions compared to feedstock collection without pretreatment. Significant uncertainties remain in terms of the costs associated with deploying torrefaction equipment at the scales modeled, but the level of potential cost savings suggest further analysis and development of these alternatives. This article is protected by copyright. All rights reserved.

Description: The potential of forests and the forest sector to mitigate greenhouse gas (GHG) emissions is widely recognized, but challenging to quantify at a national scale. Mitigation benefits through the use of forest products are affected by product lifecycles, which determine the duration of carbon storage in wood products and substitution benefits where emissions are avoided by using wood products instead of other emissions-intensive building products and energy fuels. Here we determined displacement factors for wood substitution in the built environment and bioenergy at the national level in Canada. For solid wood products, we compiled a basket of end-use products and determined the reduction in emissions for two functionally equivalent products: a more wood-intensive product versus a less wood-intensive one. Avoided emissions for end-use products basket were weighted by Canadian consumption statistics to reflect national wood uses, and avoided emissions were further partitioned into displacement factors for sawnwood and panels. We also examined two bioenergy feedstock scenarios ( constant supply and constrained supply ) to estimate displacement factors for bioenergy using an optimized selection of bioenergy facilities which maximized avoided emissions from fossil fuels. Results demonstrated that the average displacement factors were found to be similar: product displacement factors were 0.54 tC displaced per tC of used for sawnwood and 0.45 tC tC −1 for panels; energy displacement factors for the two feedstock scenarios were 0.47 tC tC −1 for the constant supply and 0.89 tC tC −1 for the constrained supply . However, there was a wide range of substitution impacts. The greatest avoided emissions occurred when wood was substituted for steel and concrete in buildings, and when bioenergy from heat facilities and/or combined heat and power facilities was substituted for energy from high-emissions fossil fuels. We conclude that (i) national-level substitution benefits need to be considered within a systems perspective on climate change mitigation to avoid the development of policies that deliver no net benefits to the atmosphere, (ii) the use of long-lived wood products in buildings to displace steel and concrete reduces GHG emissions, (iii) the greatest bioenergy substitution benefits are achieved by using a mix of facility types and capacities to displace emissions-intensive fossil fuels. This article is protected by copyright. All rights reserved.

Description: Future liquid fuel demand from renewable sources may, in part, be met by converting the seasonally wet portions of the landscape currently managed for soil and water conservation to perennial energy crops. However, this shift may increase nitrous oxide (N 2 O) emissions, thus limiting the carbon (C) benefits of energy crops. Particularly high emissions may occur during the transition period when the soil is disturbed, plants are establishing, and nitrate and water accumulation may favor emissions. We measured N 2 O emissions and associated environmental drivers during the transition of perennial grassland in a Conservation Reserve Program (CRP) to switchgrass ( Panicum virgatum L.) and Miscanthus x giganteus in the bottom 3-ha of a watershed in the Ridge and Valley ecoregion of the northeastern United States. Replicated treatments of CRP (unconverted), unfertilized switchgrass (switchgrass), nitrogen (N) fertilized switchgrass (switchgrass-N), and Miscanthus were randomized in four blocks. Each plot was divided into shoulder, backslope, and footslope positions based on the slope and moisture gradient. Soil N 2 O flux, soil moisture, and soil mineral nitrogen availability were monitored during the growing season of 2013, the year after the land conversion. Growing season N 2 O flux showed a significant vegetation-by-landscape position interaction ( P 〈 0.009). Switchgrass-N and Miscanthus treatments had 3 and 6-times higher cumulative flux respectively than the CRP in the footslope, but at other landscape positions fluxes were similar among land uses. A peak N 2 O emission event, contributing 26% of the cumulative flux, occurred after a 10.8-cm of rain during early June. Prolonged subsoil saturation coinciding with high mineral N concentration fueled N 2 O emission hot spots in the footslopes under energy crops. Our results suggest that mitigating N 2 O emissions during the transition of CRP to energy crops would mostly require a site-specific management of the footslopes. This article is protected by copyright. All rights reserved.

Description: Nitrogen (N) bioavailability is a primary limiting nutrient for crop and feedstock productivity. Associative nitrogen fixation (ANF) by diazotrophic bacteria in root-zone soil microbial communities have been shown to provide significant amounts of N to some tropical grasses, but this potential in switchgrass, a warm-season, temperate, United States native, perennial tall-grass has not been widely studied. “Alamo” and “Dacotah” are cultivars of switchgrass, adapted to the southern and northern regions of the US, respectively, and offer an opportunity to better describe this plant-bacterial association. The nitrogenase enzyme activity, microbial communities, and amino acid profiles in the root-zones of the two ecotypes were studied at three different plant growth stages. Differences in the nitrogenase enzyme activity and free soluble amino acid profiles indicated the potential for greater nitrogen fixation in the high productivity Alamo compared to the lower productivity Dacotah. Changes in the amino acid profiles and microbial community structure (rRNA genes) of the root-zone suggest different plant-bacterial interactions can help to explain differences in nitrogenase activity. PICRUSt analysis revealed functional differences, especially nitrogen metabolism, that supported ecotype differences in root-zone nitrogenase enzyme activity. It is thought that the greater productivity of Alamo increased the belowground flow of carbon into roots and root-zone habitats, which in turn, support the high-energy demands needed to support nitrogen fixation. Further research is thus needed to understand plant ecotype and cultivar trait differences that can be used to breed or genetically modify crop plants to support root-zone associations with diazotrophs. This article is protected by copyright. All rights reserved.

Description: Given the growing global population, mankind must find new ways to lower competition for land between food and fuel production. Our findings for cassava suggest that this important crop can substantially increase the combined production of both food and fuel. Cassava stems have previously been overlooked in starch and energy production. These food-crop residues contain about 30% starch (dry mass) mostly in the xylem rather than phloem tissue. Up to 15% starch of the stem dry mass can be extracted using simple water-based techniques, potentially leading to an 87% increase in global cassava starch production. The integration of biofuel production, using residues and wastewater from starch extraction, may bring added value. The cassava roots on which biofuels and other products are based can be replaced by cassava stems without land use expansion, making root starch available as food for additional 30 million people today.

Description: Willow Salix sp. is currently cultivated as a short rotation forestry crop in Ireland as a source of biomass to contribute to renewable energy goals. The aim of this study is to evaluate the energy requirements and environmental impacts associated with willow ( Salix sp .) cultivation, harvest, and transport using life cycle assessment (LCA). In this study, only emissions from the production of the willow chip are included, end-use emissions from combustion are not considered. In this LCA study, three impact categories are considered; acidification potential, eutrophication potential and global warming potential. In addition, the cumulative energy demand and energy ratio of the system are evaluated. The results identify three key processes in the production chain which contribute most to all impact categories considered; maintenance, harvest and transportation of the crop. Sensitivity analysis on the type of fertilizers used, harvesting technologies and transport distances highlights the effects of these management techniques on overall system performance. Replacement of synthetic fertilizer with biosolids results in a reduction in overall energy demand, but raises acidification potential, eutrophication potential and global warming potential. Rod harvesting compares unfavourably in comparison with direct chip harvesting in each of the impact categories considered due to the additional chipping step required. The results show that dedicated truck transport is preferable to tractor-trailer transport in terms of energy demand and environmental impacts. Finally, willow chip production compares favourably with coal provision in terms of energy ratio and global warming potential, while achieving a higher energy ratio than peat provision but also a higher global warming potential.

Description: Recent studies have introduced the metric GWP bio , an indicator of the potential global warming impact of CO 2 emissions from biofuels. When a time horizon of 100 years was applied, the studies found the GWP bio of bioenergy from slow-growing forests to be significantly lower than the traditionally calculated GWP of CO 2 from fossil fuels. This result means that bioenergy is an attractive energy source from a climate mitigation perspective. The present paper provides an improved method for quantifying GWP bio . The method is based on a model of a forest stand that includes basic dynamics and interactions of the forest's multiple carbon pools, including harvest residues, other dead organic matter, and soil carbon. Moreover, the baseline scenario (with no harvest) takes into account that a mature stand will usually continue to capture carbon if not harvested. With these methodological adjustments, the resulting GWP bio estimates are found to be two to three times as high as the estimates of GWP bio found in other studies, and also significantly higher than the GWP of fossil CO 2 , when a 100-year time horizon is applied. Hence, the climate impact per unit of CO 2 emitted seems to be even higher for the combustion of slow-growing biomass than for the combustion of fossil carbon in a 100-year time frame.

Description: A major limiting factor in the development of algae as a feedstock for the bioenergy industry is the consistent production and supply of biomass. This study is the first to access the suitability of the freshwater macroalgal genus Oedogonium to supply biomass for bioenergy applications. Specifically, we quantified the effect of CO 2 supplementation on the rate of biomass production, carbon capture, and feedstock quality of Oedogonium when cultured in large-scale outdoor tanks. Oedogonium cultures maintained at a pH of 7.5 through the addition of CO 2 resulted in biomass productivities of 8.33 (±0.51) g DW m −2  day −1 , which was 2.5 times higher than controls which had an average productivity of 3.37 (±0.75) g DW m −2  day −1 . Under these productivities, Oedogonium had a carbon content of 41–45% and a higher heating value of 18.5 MJ kg −1 , making it an ideal biomass energy feedstock. The rate of carbon fixation was 1380 g C m −2  yr −1 and 1073.1 g C m −2  yr −1 for cultures maintained at a pH of 7.5 and 8.5, and 481 g C m −2  yr −1 for cultures not supplemented with CO 2 . This study highlights the potential of integrating the large-scale culture of freshwater macroalgae with existing carbon waste streams, for example coal-fired power stations, both as a tool for carbon sequestration and as an enhanced and sustainable source of bioenergy.

Description: Crop residue resources may affect soil quality, global carbon balance, and stability of crop production, but also contribute to future energy security. This study was performed to evaluate the spatial and temporal variation in residue quantities of field crops in five provinces of North China (NC) and three provinces of Northeast China (NEC). The availability of biomass resources was derived from statistical data on crop yields for all crops on the provincial and even county level. We found that cereals – wheat, maize, and rice – were the biggest resource of crop residue feedstock. The ranking of these crops as a source of biomass for bioenergy is determined by the acreage in each region and the crop-specific yield. Annually, the average amount of total residue of 83.0 Mt (Mt = Mega tonnes) in NC (16.9 Million ha) comprised 76.6 Mt field residues and 6.4 Mt process residues on an air-dried basis. The average amount of total biomass residue of 105.7 Mt in NEC (19.8 Million ha) comprised 92.8 Mt field residues and 12.9 Mt process residues. Averaged for 2008, 2009, and 2010, the total standard coal equivalent (SCE) in NC amounted to 46.4 Mt, which comprised 42.4 Mt field residues and of 3.9 Mt process residues. In NEC, the SCE value of 57.0 Mt comprised 49.7 Mt field residues and 7.4 Mt process residues. The temporal availability of field residues was mainly concentrated in the period between July and September, followed by the period between October and December. In the period between July and September, the amount of field residue available amounted to 40.9 and 53.1 Mt in NC and NEC, respectively. An accurate assessment of field residues may guide policy makers and industry to optimize the utilization of the crop residue resource.

Description: Sustainable development of a bioenergy industry will require low-cost, high-yielding biomass feedstock of desirable quality. Switchgrass ( Panicum virgatum L.) is one of the primary feedstock candidates in North America, but the potential to grow this biomass crop using fertility from biosolids has not been fully explored. The objective of this study was to examine the effects of harvest frequency and biosolids application on switchgrass in Virginia, USA. ‘Cave-in-Rock’ switchgrass from well-established plots was cut once (November) or twice (July and November) per year between 2010 and 2012. Class A biosolids were applied once at rates of 0, 153, 306, and 459 kg N ha −1 in May 2010. Biomass yield, neutral and acid detergent fiber, cellulose, hemicellulose, lignin, and ash were determined. Theoretical ethanol potential (TEP, l ethanol Mg −1 biomass) and yield (TEY, l ethanol ha −1 ) were calculated based on cellulose and hemicellulose concentrations. Cutting twice per season produced greater biomass yields than one cutting (11.7 vs. 9.8 Mg ha −1 ) in 2011, but no differences were observed in other years. Cutting once produced feedstock with greater TEP (478 vs. 438 l Mg −1 ), but no differences in TEY between cutting frequencies. Biosolids applied at 153, 306, and 459 kg N ha −1 increased biomass yields by 25%, 37%, and 46%, and TEY by 25%, 34%, and 42%, respectively. Biosolids had inconsistent effects on feedstock quality and TEP. A single, end-of-season harvest likely will be preferred based on apparent advantages in feedstock quality. Biosolids can serve as an effective alternative to N fertilizer in switchgrass-to-energy systems.

Description: Four biochar types, produced by slow pyrolysis of poultry litter (PL) and pine chips (P) at 400 or 500 °C, were added to two adjacent soils with contrasting soil organic matter (SOM) content (8.9 vs. 16.1 g C kg −1 ). The N mineralization rate was determined during 14-week incubations and assessments were made of the microbial biomass C, dehydrogenase activity, and the microbial community structure (PLFA-extraction). The addition of PL biochars increased the net N mineralization (i.e., compared to the control treatment) in both soils, while for treatments with P biochars net N immobilization was observed in both soils. Increasing the pyrolysis temperature of both feedstock types led to a decrease in net N mineralization. The ratio of Bacterial to Fungal PLFA biomarkers also increased with addition of biochars, and particularly in the case of the 500 °C biochars. Next to feedstock type and pyrolysis temperature, SOM content clearly affected the assessed soil biological parameters, viz. net N mineralization or immobilization, MBC and dehydrogenase activity were all greater in the H soil. This might be explained by an increased chance of physical contact between the microbial community activated by SOM mineralization upon incubation and discrete biochar particles. However, when considering the H soil's double C and N content, these responses were disproportionally small, which may be partly due to the L soil's, somewhat more labile SOM. Nonetheless, increasing SOM content and microbial biomass and activity generally appears to result in greater mineralization of biochar. Additionally, higher N mineralization after PL addition to the H soil with lower pH than the L soil can be due to the liming effect of the PL biochars.

Description: Plant cell walls are composed of cellulose microfibrils embedded in a cross-linked-net of matrix polysaccharides and co-polymerized with lignin. The study presented the genotypic variations of cell wall composition, biohydrogen production, and lignocellulose degradation ratio in a collection of 102 Miscanthus sinensis ( M . Sinensis , hereafter) accessions collected from a wide geographical range in China. Significant variations were observed for the determined traits, cellulose content, hemicellulose content, cellulose and hemicellulose degradation efficiency, and biohydrogen yield. The cellulose, hemicellulose, and lignin contents ranged from 30.20–44.25, 28.97–42.65, and 6.96–20.75%, respectively. The degradation ratio of cellulose and hemicellulose varied from 2.08% to 37.87% and from 14.71% to 52.50%, respectively. The feedstock was fermented to produce biohydrogen, and the production varied from 14.59 to 40.66 ml per gram of Miscanthus biomass. The expression profile of three cellulose synthase ( MsCesA ) genes was initially established to indicate the genotypic difference among the M . sinensis accessions. Pearson's correlations were conducted to reveal the perplexing relationship between the tested traits, biohydrogen yield, cell wall composition and their degradation efficiency. In addition, the relationship pattern, between the test traits and the geographic factors corresponding with the original place, was investigated. The result showed that the significant variation among the M . sinensis genotypes is the result of natural selection in different environments of their original habitats. Improvement in cell wall composition and structure and enhancement of lignocellulose degradation ratio could significantly increase sustainable bioenergy production.

Description: For the C4 perennial grasses, Miscanthus  ×  giganteus and Panicum virgatum (switchgrass) to be successful for bioenergy production they must maintain high yields over the long term. Previous studies under the less conducive climate for productivity in N.W. Europe found little or no yield decline in M . ×  giganteus in the long term. This study provides the first analysis of whether yield decline occurs in M . ×  giganteus under United States. Midwest conditions in side-by-side trials with P. virgatum over 8–10 years at seven locations across Illinois. The effect of stand age was determined by using a linear regression model that included effects of weather. Miscanthus  ×  giganteus produced yields more than twice that of P. virgatum averaging 23.4 ± 1.2 Mg ha −1  yr −1 and 10.0 ± 0.9 Mg ha −1  yr −1 , respectively, averaged over 8–10 years. Relationships of yield with precipitation and growing degree days were established and used to estimate yields corrected for the stochastic effects of weather. Across all locations and in both species, yield initially increased until it reached a maximum during the fifth growing season and then declined to a stable, but lower level in the eighth. This pattern was more pronounced in M . ×  giganteus . The mean yields observed over this longer term period of 8–10 years were lower than the yields of the first 5 years. However, this decline was proportionately greater in M . ×  giganteus than in P. virgatum, suggesting a stronger effect of stand age on M . ×  giganteus . Based on the average yield over the period of this study, meeting the United States Renewable Fuel Standard mandate of 60 billion liters of cellulosic ethanol by 2022, would require 6.8 Mha of M . ×  giganteus or 15.8 Mha of P. virgatum . These appear manageable numbers for the United States, given the 16.0 Mha in the farmland Conservation Reserve Program in addition to another 13.0 Mha abandoned from agriculture in the last decade.

Description: Short-rotation woody biomass crops (SRWC) have been proposed as a major feedstock source for bioenergy generation in the Northeastern US. To quantify the environmental effects and greenhouse gas (GHG) balance of crops including SRWC, investigators need spatially explicit data which encompass entire plantation cycles. A knowledge gap exists for the establishment period which makes current GHG calculations incomplete. In this study, we investigated the effects of converting pasture and hayfields to willow ( Salix spp.) and hybrid-poplar ( Populus spp.) SRWC plantations on soil nitrogen (N) cycling, nitrous oxide (N 2 O) emissions, and nitrate ( NO 3 − ) leaching at six sites of varying soil and climate conditions across northern Michigan and Wisconsin, following these plantations from pre conversion through their first 2 years. All six sites responded to establishment with increased N 2 O emissions, available inorganic N, and, where it was measured, NO 3 − leaching; however, the magnitude of these impacts varied dramatically among sites. Soil NO 3 − levels varied threefold among sites, with peak extractable NO 3 − concentrations ranging from 15 to 49 g N kg −1 soil. Leaching losses were significant and persisted through the second year, with 44–112 kg N ha −1 leached in SRWC plots. N 2 O emissions in the first growing season varied 30-fold among sites, from 0.5 to 17.0 Mg- CO 2 eq  ha −1 (carbon dioxide equivalents). N 2 O emissions over 2 years resulted in N 2 O emissions due to plantation establishment that ranged from 0.60 to 22.14 Mg- CO 2 eq  ha −1 above baseline control levels across sites. The large N losses we document herein demonstrate the importance of including direct effects of land conversion in life-cycle analysis (LCA) studies of SRWC GHG balance. Our results also demonstrate the need for better estimation of spatial variability of N cycling processes to quantify the full environmental impacts of SRWC plantations.

Description: Jatropha curcas L. is a tropical tree grown on large scale as a potential biofuel seed crop. However, little information on the reproductive ecology of the species is available. This lack of knowledge makes it hard to predict yield. The higher number of male flowers than female flowers results in a very low yield. In this context, field experiments were conducted in mature (site 1) and young (site 2) plantations in Zambia and mature plantation (site 3) in Malawi to study flowering characteristics and the effect of pollination methods on the fruiting and seed yield of J. curcas . Pollination treatments were open pollination, autogamous pollination, self-pollination, cross-pollination and pollen supplemented open pollination. The result showed J. curcas is not only of protandrous nature as reported earlier. The male female flower sex ratio was 17 : 1, 22 : 1 and 10 : 1, respectively, for site 1 and 2 in Zambia and site 3 in Malawi. The mean flower longevity periods were 1.80 ± 0.07 days for male and 4.5 ± 0.18 days for female. Fewer fruit set and seed yield were recorded from autogamous pollination in Zambia sites. In the case of Malawi, more matured fruits resulted from autogamous pollination but the fruits contained fewer seeds. High fruit and seed yield were recorded for open pollination similar to pollen-supplemented pollination at Zambia sites, which indicates there was no pollen limitation in these sites. In the Malawi site there was no seed yield difference between pollination treatments. The experiment showed that J. curcas can be both protandrous and protogynous and able to produce seeds through both self-and cross-pollination. The natural fruit set and seed yield indicates that stimulating natural pollination will improve J. curcas fruit set and seed yield.

Description: British Columbia (BC) forests are estimated to have become a net carbon source in recent years due to tree death and decay caused primarily by mountain pine beetle (MPB) and related post-harvest slash burning practices. BC forest biomass has also become a major source of wood pellets, exported primarily for bioenergy to Europe, although the sustainability and net carbon emissions of forest bioenergy in general are the subject of current debate. We simulated the temporal carbon balance of BC wood pellets against different reference scenarios for forests affected by MPB in the interior BC timber harvesting area using the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3). We evaluated the carbon dynamics for different insect-mortality levels, at the stand- and landscape level, taking into account carbon storage in the ecosystem, wood products and fossil fuel displacement. Our results indicate that current harvesting practices, in which slash is burnt and only sawdust used for pellet production, require between 20–25 years for beetle-impacted pine and 37–39 years for spruce-dominated systems to reach pre-harvest carbon levels (i.e. break-even) at the stand-level. Using pellets made from logging slash to replace coal creates immediate net carbon benefits to the atmosphere of 17–21 tonnes C ha −1 , shortening these break-even times by 9–20 years and resulting in an instant carbon break-even level on stands most severely impacted by the beetle. Harvesting pine dominated sites for timber while using slash for bioenergy was also found to be more carbon beneficial than a protection reference scenario on both stand- and landscape level. However, harvesting stands exclusively for bioenergy resulted in a net carbon source unless the system contained a high proportion of dead trees (〉85%). Systems with higher proportions of living trees provide a greater climate change mitigation if used for long lived wood products.

Description: The Nobel environmental productivity index (EPI) was used as a framework for the development of a predictive geospatial model to estimate the bioethanol yield potential of four crassulacean acid metabolism (CAM) candidates in Australia ( Agave fourcroydes , Agave salmiana , Agave tequilana , and Opuntia ficus-indica ). GIS software was used to integrate climate datasets with titratable acidity responses to changes in photosynthetically active radiation (PAR), temperature, and water availability. Additional refinements to Nobel's approach were made to accommodate spatial and temporal fluctuations in soil water potential (ψs) as a function of soil particle size distribution and precipitation, and CO 2 uptake response to a range of day and night temperatures. A scalar factor for CO 2 persistence during periods of drought was also introduced to model the capacity of succulent species of Agave to buffer against fluctuations in ψs. Macro-scale criteria were applied to estimate environmentally responsible (ER) bioethanol yield potential on lands that are not suitable for food production. Consideration was given to indigenous vascular plant species richness and endemism scores at ER sites of interest. The highest mean ER bioethanol yield was achieved by A. fourcroydes (μ: 3.89, max. 7.17 kL ha -1 yr -1 ) while the highest maximum yield was achieved by A. tequilana (μ: 3.78, max. 7.63 kL ha -1 yr -1 ). This research indicated the CAM pathway may produce significant yields (≥≥ 5 kL ha -1 yr -1 ) at ER sites totalling 57,700 km 2 (0.7% land area of Australia).

Description: Biochar management has been proposed as a possible tool to mitigate anthropogenic CO 2 emissions, and thus far its impacts in forested environments remain poorly understood. We conducted a large scale, replicated field experiment using 0.05 ha plots in the boreal region in Northern Sweden to evaluate how soil and vegetation properties and processes responded to biochar application and the disturbance associated with burying biochar in the soil. We employed a randomized block design, where biochar and soil mixing treatments were established in factorial combination (i.e. control, soil mixing-only, biochar-only, and biochar and soil mixing; n=6 plots of each). After two growing seasons, we found that biochar application enhanced net soil N mineralization rates and soil NH 4 + concentrations regardless of the soil mixing treatment, but had no impact on the availability of NO 3 - , the majority of soil microbial community parameters, or soil respiration. Meanwhile, soil mixing enhanced soil NO 3 - concentrations, but had negative impacts on net N mineralization rates and several soil microbial community variables. Many of the effects of soil mixing on soil nutrient and microbial community properties were less extreme when biochar was also added. Biochar addition had almost no effects on vegetation properties (except for a small reduction in species richness of the ground layer vegetation), while soil mixing caused significant reductions in graminoid and total ground layer vegetation cover, and enhanced seedling survival rates of P. sylvestris, and seed germination rates for four tree species. Our results suggest that biochar application can serve as an effective tool to store soil C in boreal forests while enhancing NH 4 + availability. They also suggest that biochar may serve as a useful complement to site preparation techniques that are frequently used in the boreal region, by enhancing soil fertility and reducing nutrient losses when soils are scarified during site preparation. This article is protected by copyright. All rights reserved.

Description: Greenhouse gas (GHG) emissions from soils are a key sustainability metric of cropping systems. During crop establishment, disruptive land-use change is known to be a critical, but under reported period, for determining GHG emissions. We measured soil N 2 O emissions and potential environmental drivers of these fluxes from a three-year establishment-phase bioenergy cropping systems experiment replicated in southcentral Wisconsin (ARL) and southwestern Michigan (KBS). Cropping systems treatments were annual monocultures (continuous corn, corn–soybean–canola rotation), perennial monocultures (switchgrass, miscanthus, and poplar), and perennial polycultures (native grass mixture, early successional community, and restored prairie) all grown using best management practices specific to the system. Cumulative three-year N 2 O emissions from annuals were 142% higher than from perennials, with fertilized perennials 190% higher than unfertilized perennials. Emissions ranged from 3.1 to 19.1 kg N 2 O-N ha −1 yr −1 for the annuals with continuous corn 〉 corn–soybean–canola rotation and 1.1 to 6.3 kg N 2 O-N ha −1 yr −1 for perennials. Nitrous oxide peak fluxes typically were associated with precipitation events that closely followed fertilization. Bayesian modeling of N 2 O fluxes based on measured environmental factors explained 33% of variability across all systems. Models trained on single systems performed well in most monocultures (e.g., R 2  = 0.52 for poplar) but notably worse in polycultures (e.g., R 2  = 0.17 for early successional, R 2  = 0.06 for restored prairie), indicating that simulation models that include N 2 O emissions should be parameterized specific to particular plant communities. Our results indicate that perennial bioenergy crops in their establishment phase emit less N 2 O than annual crops, especially when not fertilized. These findings should be considered further alongside yield and other metrics contributing to important ecosystem services.

Description: Miscanthus is a perennial C 4 grass that has recently become an important bioenergy crop. The efficiency of breeding improved Miscanthus biomass cultivars could be greatly increased by marker-assisted selection. Thus, a high density genetic map is critical to Miscanthus improvement. In this study, a mapping population of 261 F 1 progeny was developed from a cross between two diploid M. sinensis cultivars, ‘Strictus’ and ‘Kaskasde’. High density genetic maps for the two parents were produced with 3,044 newly developed single nucleotide polymorphisms (SNPs) obtained from restriction-site associated DNA sequencing, and 138 previously mapped GoldenGate SNPs. The female parent (‘Strictus’) map spanned 1,599 cM, with 1,989 SNPs on 19 linkage groups, and an average inter-marker spacing of 0.8 cM. The length of the male parent (‘Kaskade’) map was 1,612 cM, with 1,821 SNPs, and an average inter-marker spacing of 0.9 cM. The utility of the map was confirmed by locating quantitative trait loci (QTL) for the zebra stripe trait, which was segregating in this population. Three QTL for zebra stripe presence/absence ( zb1 , zb2 on LG 7, and zb3 on LG 10) and three for zebra stripe intensity ( zbi1 , zbi2 , zbi3 on LGs 7, 10, 3) were identified. Each allele that caused striping was recessive. Incomplete penetrance was observed for each zb QTL, but penetrance was greatest when two or more zb QTL were homozygous for the causative alleles. Similarly, the intensity of striping was greatest when two or more zbi QTL were homozygous for alleles that conferred the trait. Comparative mapping indicated putative correspondence between zb3 and/or zbi2 on LG 10 to previously sequenced genes conferring zebra stripe in maize and rice. These results demonstrate that the new map is useful for identifying marker-trait associations. The mapped markers will become a valuable community resource, facilitating comparisons among studies and the breeding of Miscanthus . This article is protected by copyright. All rights reserved.

Description: Rice straw can serve as potential material for bioenergy production. However the quantitative effects of increasing atmospheric carbon dioxide concentration [CO 2 ] on rice straw quality, and the resulting consequences for bioenergy utilization are largely unknown. In this study, two rice varieties, WYJ and LY, that have been shown previously to have a weak and strong stimulatory response to rising [CO 2 ], respectively were grown with and without additional CO 2 at China FACE (free air carbon dioxide enrichment) platform. Qualitative and quantitative measurements in response to [CO 2 ] included straw biomass (including leaf, sheath and stem), the concentration of nonstructural and structural carbohydrates, the syringyl to guaiacyl (S/G) ratio of lignin, glucose and xylose release from structural carbohydrate, total sugar release by enzymatic saccharification, as well as sugar yield and the ratio of cellulose and hemicellulose degradation. Elevated [CO 2 ] significantly increased straw biomass and nonstructural carbohydrates contents while enhancing the degraded ratio of structural carbohydrates as indicated by the decreased lignin content and increased S/G ratio. Overall, total sugar yield (g m -2 ) in rice straw significantly increased by 27.1 and 57% for WYJ and LY at elevated [CO 2 ], respectively. These findings, while preliminary, suggest that rice straw quality and potential biofuel utilization may improve as a function of rising [CO 2 ]. This article is protected by copyright. All rights reserved.

Description: Though forest biomass energy was long assumed to be carbon neutral, many studies show delays between forest biomass carbon emissions and sequestration, with biomass carbon causing climate-change damage in the interim. While some models suggest that these primary biomass carbon effects may be mitigated by induced market effects, e.g. from landowner decisions to increase afforestation due to higher biomass prices, the delayed carbon sequestration of biomass energy systems still creates considerable scientific debate (i.e. how to assess effects) and policy debate (i.e. how to act given these effects). Forests can be carbon sinks, but their carbon absorption capacity is finite. Filling the sink with fossil-fuel carbon thus has a cost, and conversely, harvesting a forest for biomass energy—which depletes the carbon sink—creates potential benefits from carbon sequestration. These values of forest carbon sinks have not generally been considered. Using data from the 2010 Manomet Center for Conservation Sciences “Biomass sustainability and carbon policy study” and a model of forest biomass carbon system dynamics, we investigate how discounting future carbon flows affects the comparison of biomass energy to fossil fuels in Massachusetts, USA. Drawing from established financial valuation metrics, we calculate internal rates of return (IRR) as explicit estimates of the temporal values of forest biomass carbon emissions. Comparing these IRR to typical private discount rates, we find forest biomass energy to be preferred to fossil fuel energy in some applications. We discuss possible rationales for zero and near-zero social discount rates with respect to carbon emissions, showing that social discount rates depend in part on expectations about how climate change affects future economic growth. With near-zero discount rates, forest biomass energy is preferred to fossil fuels in all applications studied. Higher-IRR biomass energy uses (e.g. thermal applications) are preferred to lower-IRR uses (e.g. electricity generation without heat recovery). This article is protected by copyright. All rights reserved.

Description: Bioenergy is expected to play an important role in the future energy mix as it can substitute fossil fuels and contribute to climate change mitigation. However, large-scale bioenergy cultivation may put substantial pressure on land and water resources. While irrigated bioenergy production can reduce the pressure on land due to higher yields, associated irrigation water requirements may lead to degradation of freshwater ecosystems and to conflicts with other potential users. In this article, we investigate the trade-offs between land and water requirements of large-scale bioenergy production. To this end, we adopt an exogenous demand trajectory for bioenergy from dedicated energy crops, targeted at limiting greenhouse gas emissions in the energy sector to 1100 Gt carbon dioxide equivalent until 2095. We then use the spatially explicit global land- and water-use allocation model MAgPIE to project the implications of this bioenergy target for global land and water resources. We find that producing 300 EJ yr −1 of bioenergy in 2095 from dedicated bioenergy crops is likely to double agricultural water withdrawals if no explicit water protection policies are implemented. Since current human water withdrawals are dominated by agriculture and already lead to ecosystem degradation and biodiversity loss, such a doubling will pose a severe threat to freshwater ecosystems. If irrigated bioenergy production is prohibited to prevent negative impacts of bioenergy cultivation on water resources, bioenergy land requirements for meeting a 300 EJ yr −1 bioenergy target increase substantially (+ 41%) – mainly at the expense of pasture areas and tropical forests. Thus, avoiding negative environmental impacts of large-scale bioenergy production will require policies that balance associated water and land requirements.

Description: Biomass production on low-grade land is needed to meet future energy demands and minimise resource conflicts. This, however, requires improvements in plant water use efficiency (WUE) that are beyond conventional C3 and C4 dedicated bioenergy crops. Here we present the first global-scale geographic information system (GIS) based productivity model of two highly water-efficient crassulacean acid metabolism (CAM) candidates: Agave tequilana and Opuntia ficus-indica . Features of these plants that translate to WUE advantages over C3 and C4 bioenergy crops include nocturnal stomatal opening, rapid rectifier-like root hydraulic condsuctivity responses to fluctuating soil water potential, and the capacity to buffer against periods of drought. Yield simulations for the year 2070 were performed under the four representative concentration pathway (RCPs) scenarios presented in the IPCC's 5th Assessment Report. Simulations on low-grade land suggest that O. ficus-indica alone has the capacity to meet ‘extreme’ bioenergy demand scenarios (〉600 EJ yr -1 ) and is highly resilient to climate change (-1%). Agave tequilana is moderately impacted (-11%). These results are significant because bioenergy demand scenarios 〉 600 EJ yr -1 could be met without significantly increasing conflicts with food production and contributing to deforestation. Both CAM candidates outperformed the C4 bioenergy crop, Panicum virgatum L. (switchgrass) in arid zones in the latitudinal range 30 o S - 30 o N. This article is protected by copyright. All rights reserved.

Description: Residual pollutants including polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and carbon(aceous) nanoparticles are inevitably generated during the pyrolysis of waste biomass, and remain on the solid co-product called biochar. Such pollutants could have adverse effects on the plant growth as well as microbial community in soil. Although biochar has been proposed as a “carbon negative strategy” to mitigate the greenhouse gas emissions, the impacts of its application with respect to long-term persistence and bioavailability of hazardous components are not clear. Moreover, the co-occurrence of low molecular weight VOCs with PAHs in biochar may exert further phytotoxic effects. This review describes the basic need to unravel key mechanisms driving the storage versus emission of these organics and the dynamics between the sorbent (biochar) and soil microbes. Moreover, there is an urgent requirement for standardized methods for quantitative analysis of PAHs and VOCs in biochar under environmentally relevant conditions. Current research gap includes the influence of biochar application technology on the short- and long-term fate of PAHs and VOCs, long-term studies on PAHs/VOCs release, and for proper control of biochar quality and associated risk assessment. This article is protected by copyright. All rights reserved.

Description: New and comprehensive collections of the perennial rhizomatous reed canary grass ( Phalaris arundinacea ) were made in NW Europe along north to south and east to west clines from Denmark, Germany, Ireland, Poland, Sweden and the UK. Rhizome, seed and leaf samples were taken for analysis and genetic resource conservation. A subsample covering the geographic range was characterized using plastid genome sequencing and SNP discovery generated using a long-read PCR and MiSeq sequencing approach. Samples were also subject to flow cytometry and all found to be tetraploid. New sequences were assembled against a Lolium perenne (perennial ryegrass) reference genome and an average of approximately 60% of each genome was aligned (81,064bp). Genetic variation was high among the 48 sequenced genotypes with a total of 1,793 SNPs, equating to 23 SNPs/kbp. SNPs were subject to principal coordinate and Structure analyses to detect population genetic groupings and to examine phylogeographical pattern. Results indicate substantial genetic variation and population genetic structuring of this allogamous species at a broad geographic scale in NW Europe with plastid genetic diversity organized more across an east to west than a north to south cline. This article is protected by copyright. All rights reserved.

Description: Growing energy crops on marginal land has been promoted as a way of ensuring that biomass production involves an acceptable and sustainable use of land. Saline and saline-prone agricultural lands represent an opportunity for growing energy crops avoiding the displacement of food production and contributing to restoration of degraded land. Giant reed ( Arundo donax L.) is a perennial grass that has been proposed as a promising energy crop for lignocellulosic biomass production whilst its tolerance to salinity has been proved. In this work the identification of surplus saline lands that could be irrigated with saline waters for growing tolerant-energy crops (giant reed) in the mainland of Spain and the assessment of the agronomically attainable yield in these limiting growing conditions were undertaken. To this purpose, a GIS analysis was conducted using geodatabases related to saline areas, agro-climatic conditions, irrigation water requirements, agricultural land availability, restrictions regarding the range of electrical conductivity tolerated by the crop, competition with agro-food crops and irrigation water provisions. According to the approach developed, the irrigated and saline agricultural area available and suitable for biomass production from giant reed amounted up to 34,412 ha. The agronomically attainable yield in these limiting conditions was estimated at 12.7 – 22.2 t dm·ha −1 ·year −1 and the potential production of lignocellulosic biomass, 597,338 t dm·year −1 . The methodology followed in this study can be applied to other target regions; it allows the identification of this type of marginal lands, where salinity-tolerant plant species could be grown for bioenergy purposes, avoiding competition with agro-food crops, and where soil restoration measurements should be undertaken. This article is protected by copyright. All rights reserved.

Description: Spatially accurate and reliable estimates from fast-growing plantations are a key factor for planning energy supply. The present paper aims to estimate the yield of biomass from short rotation willow plantations in Northern Europe. The data was based on harvesting records from 1790 commercial plantations in Sweden, grouped into three ad-hoc categories: low, middle and high performance. The predictors included climatic variables, allowing the spatial extrapolation to nearby countries. The modeling and spatialization of the estimates used Boosted Regression Trees, a method based on machine learning. The average RMSE for the final models selected were 0.33, 0.39 and 1.91 (corresponding to R 2 =0.77, 0.88 and 0.45), for the low, medium and high performance categories, respectively. The models were then applied to obtain 1x1 km yield estimates in the rest of Sweden, as well as for Norway, Denmark, Finland, Estonia, Latvia, Lithuania and the Baltic coast of Germany and Poland. The results demonstrated a large regional variation. For the first rotation under high performance conditions, the country averages were: 〉7 odt ha −1 yr −1 in the Baltic coast of Germany, 〉6 odt ha −1 yr −1 in Denmark, 〉5 odt ha −1 yr −1 in the Baltic coast of Poland, and between 4-5 odt ha −1 yr −1 in the rest. The results of this approach indicate that they can provide faster and more accurate predictions than previous modelling approaches, and can offer interesting possibilities in the field of yield modelling. This article is protected by copyright. All rights reserved.

Description: Converting land to biofuel feedstock production incurs changes in soil organic carbon (SOC) that can influence biofuel life-cycle greenhouse gas (GHG) emissions. Estimates of these land use change (LUC) and life-cycle GHG emissions affect biofuels’ attractiveness and eligibility under a number of renewable fuel policies in the U.S. and abroad. Modeling was used to refine the spatial resolution and depth-extent of domestic estimates of SOC change for land (cropland, cropland pasture, grasslands, and forests) conversion scenarios to biofuel crops (corn, corn stover, switchgrass, Miscanthus , poplar, and willow) at the county level in the U.S. Results show that in most regions, conversions from cropland and cropland pasture to biofuel crops led to neutral or small levels of SOC sequestration, while conversion of grassland and forest generally caused net SOC loss. SOC change results were incorporated into the Greenhouse Gases, Regulated Emissions, and Energy use in Transportation (GREET) model to assess their influence on life-cycle GHG emissions of corn and cellulosic ethanol. Total LUC GHG emissions (g CO 2 eq MJ −1 ) were 2.1–9.3 for corn-, -0.7 for corn stover-, -3.4–12.9 for switchgrass-, and -20.1–-6.2 for Miscanthus ethanol; these varied with SOC modeling assumptions applied. Extending the soil depth from 30 to 100cm affected spatially-explicit SOC change and overall LUC GHG emissions; however the influence on LUC GHG emissions estimates were less significant in corn and corn stover than cellulosic feedstocks. Total life-cycle GHG emissions (g CO 2 eq MJ −1 , 100cm) were estimated to be 59–66 for corn ethanol, 14 for stover ethanol, 18-26 for switchgrass ethanol, and -7–-0.6 for Miscanthus ethanol. The LUC GHG emissions associated with poplar- and willow-derived ethanol may be higher than that for switchgrass ethanol due to lower biomass yield. This article is protected by copyright. All rights reserved.

Description: Land to produce biomass is essential if the United States is to expand bioenergy supply. Use of agriculturally marginal land avoids the food vs fuel problems of food price rises and carbon debt that are associated with crop and forest land. Recent remote sensing studies have identified large areas of U.S. marginal land deemed suitable for bioenergy crops. Yet the sustainability benefits of growing bioenergy crops on marginal land only pertain if land is economically available. Scant attention has been paid to the willingness of landowners to supply land for bioenergy crops. Focusing on the northern tier of the Great Lakes, where grassland transitions to forest and land prices are low, this contingent valuation study reports on the willingness of a representative sample of 1107 private, non-corporate landowners to rent land for three bioenergy crops: corn, switchgrass, and poplar. Of the 11% of land that was agriculturally marginal, they were willing to make available no more than 21% for any bioenergy crop (switchgrass preferred on marginal land) at double the prevailing land rental rate in the region. At the same generous rental rate, of the 28% that is cropland they would rent up to 23% for bioenergy crops (corn preferred), while of the 55% that is forest land, they would rent up to 15% for bioenergy crops (poplar preferred). Regression results identified deterrents to land rental for bioenergy purposes included appreciation of environmental amenities and concern about rental disamenities. In sum, like landowners in the southern Great Lakes region, landowners in the Northern Tier are reluctant to supply marginal land for bioenergy crops. If rental markets existed, they would rent more crop and forest land for bioenergy crops than they would marginal land, which would generate carbon debt and opportunity costs in wood product and food markets. This article is protected by copyright. All rights reserved.

Description: The possibility of using bioenergy as a climate change mitigation measure has sparked a discussion of whether and how bioenergy production contributes to sustainable development. We undertook a systematic review of the scientific literature to illuminate this relationship and found a limited scientific basis for policy-making. Our results indicate that knowledge on the sustainable development impacts of bioenergy production is concentrated in a few well-studied countries, focuses on environmental and economic impacts, and mostly relates to dedicated agricultural biomass plantations. The scope and methodological approaches in studies differ widely and only a small share of the studies sufficiently reports on context and/or baseline conditions, which makes it difficult to get a general understanding of the attribution of impacts. Nevertheless we identified regional patterns of positive or negative impacts for all categories – environmental, economic, institutional, social and technological. In general, economic and technological impacts were more frequently reported as positive, while social and environmental impacts were more frequently reported as negative (with the exception of impacts on direct substitution of GHG emission from fossil fuel). More focused and transparent research is needed to validate these patterns and develop a strong science underpinning for establishing policies and governance agreements that prevent/mitigate negative and promote positive impacts from bioenergy production. This article is protected by copyright. All rights reserved.

Description: Biogas could provide a more sustainable energy source than woodfuels for rural households in Sub-Saharan African. However, functioning of biogas digesters can be limited in areas of low water availability. The water required is approximately 50 dm 3 day −1 for each cow and 10 dm 3 day −1 for each pig providing manure to the digester, or 25 (±6) dm 3 day −1 for each person in the household, using a digester volume of 1.3 (±0.3) m 3 capita −1 . Here we consider the potential of domestic water recycling, rainwater harvesting and aquaculture to supply the water needed for digestion in different countries of Sub-Saharan Africa. Domestic water recycling was found to be important in every country but was usually insufficient to meet the requirements of the digester, with households in 72% of countries needing to collect additional water. Rooftop rainwater harvesting also has an important role, iron roofs being more effective than thatched roofs at collecting water. However, even with an iron roof, the size of roof commonly found in Sub-Saharan Africa (15 m 2 to 40 m 2 ) is too small to collect sufficient water, requiring an extra area (in m 2 ) for each person of (where R is the rainfall in mm). If there is a local market for fish, stocking a pond with tilapia, fed on plankton growing on bioslurry from the digester, could provide an important source of additional income and hold the water required by the digester. In areas where rainfall is low and seasonal, the fishpond might be stocked only in the rainy season, allowing the pond to be covered during the dry period to reduce evaporation. If evaporative losses ( E in mm) exceed rainfall, an extra catchment area is needed to maintain the water level in the pond, equivalent to approximately m 2 for each person in the household. This article is protected by copyright. All rights reserved.

Description: A wealth of data and information on the cultivation of perennial biomass crops has been collected, but direct comparisons between herbaceous and woody crops are rare. The main objective of this research was to compare the biomass yield, the energy balance and the biomass quality of six perennial bioenergy crops: Populus spp., Robinia pseudoacacia, Salix spp. and Arundo donax, Miscanthus ×giganteus, Panicum virgatum, grown in two marginal environments. For giant reed and switchgrass two levels of nitrogen fertilization were applied annually (0-100 kg ha −1 ). Nitrogen fertilization did not affect biomass or energy production of giant reed, thus it significantly reduced the Energy Return On Investment (EROI) (from 73 to 27). In switchgrass, nitrogen fertilization significantly increased biomass production and the capacity of this crop to respond to water availability, making it a favorable option when only biomass production is a target. Net Energy Gain (NEG) was higher for herbaceous crops than for woody crops. In Casale, EROI calculated for poplar and willow (7, on average) was significantly lower than that of the other crops (14, on average). In Gariga, the highest EROI was calculated for miscanthus (98), followed by no-fertilized giant reed and switchgrass (82 and 73, respectively). Growing degree days 10 during the cropping season had no effect on biomass production in any of the studied species, though water availability from May to August was a major factor affecting biomass yield in herbaceous crops. Overall, herbaceous crops had the highest ranking for bioenergy production due to their high biomass yield, high net energy gain (NEG) and their biomass quality that renders them suitable to both biochemical and thermochemical conversion. Miscanthus in particular had the highest EROI in both locations (16 and 98, in Casale and Gariga), while giant reed had the highest NEG on the silty-loam soil of Gariga. This article is protected by copyright. All rights reserved.

Description: In this paper the below- and above-ground biomass production in bioenergy buffers and biogeochemical N removal processes along the soil-groundwater continuum were assessed. In a sandy loam soil with shallow groundwater, bioenergy buffers of miscanthus and willow (5 and 10 m wide) were planted along a ditch of an agricultural field (AF) located in the Po valley (Italy). Mineral N forms and dissolved organic C (DOC) were monitored monthly over an 18 month period in groundwater before and after the bioenergy buffers. Soil samples were measured for inorganic N, DOC, microbial biomass C (MBC) and N (MBN), and potential nitrate reductase activity (NRA). The results indicated that bioenergy buffers are able to efficiently remove from groundwater the incoming NO 3 -N (62%-5 m and 80%-10 m). NO 3 -N removal rate was higher when nitrate input from AF increased due to N fertilization. Willow performed better than miscanthus in terms of biomass production (17 Mg DM ha −1 y −1 ), fine root biomass (5.3 Mg ha −1 ) and N removal via harvesting (73 kg N ha −1 ). The negative nonlinear relationship found between NO 3 -N and DOC along the soil-groundwater continuum from AF to bioenergy buffers indicates that DOC:NO 3 -N ratio is an important controlling factor for promoting denitrification in bioenergy buffers. Bioenergy buffers promoted soil microbial functioning as they stimulated plant–microbial linkages by increasing the easily available C sources for microorganisms (as DOC). First, willow and miscanthus promoted high rates of biological removal of nitrate (NRA) along the soil profile. Second, rhizosphere processes activated the soil microbial community leading to significant increases in MBC and microbial N immobilization. Herbaceous and woody bioenergy crops have been confirmed as providing good environmental performances when cultivated as bioenergy buffers by mitigating the disservices of agricultural activities such as groundwater N pollution. This article is protected by copyright. All rights reserved.

Description: Residue removal for biofuel production may have unintended consequences for N 2 O emissions from soils, and it is not clear how N 2 O emissions are influenced by crop residue removal from different tillage systems. Thus, we measured field-scale N 2 O flux over five years (2005-2007, 2010-2011) from an annual crop rotation to evaluate how N 2 O emissions are influenced by no-till (NT) compared to conventional tillage (CV), and how crop residue removal (R-) rather than crop residue return to soil (R+) affects emissions from these two tillage systems. Data from all five years indicated no differences in N 2 O flux between tillage practices at the onset of the growing season, but CT had 1.4 to 6.3 times higher N 2 O flux than NT overwinter. Nitrous oxide emissions were higher due to R- compared to R+, but the effect was more marked under CT than NT and overwinter than during spring. Our results thus challenge the assumption based on IPCC methodology that crop residue removal will result in reduced N 2 O emissions. The potential for higher N 2 O emission with residue removal implies that the benefit of utilizing biomass as biofuels to mitigate greenhouse gas emission may be overestimated. Interestingly, prior to an overwinter thaw event soil dissolved organic C (DOC) was negatively correlated to peak N 2 O flux (r = -0.93). This suggests that lower N 2 O emissions with R+ vs R- may reflect more complete stepwise denitrification to N 2 during winter and possibly related to the heterotrophic microbial capacity for processing crop residue into more soluble C compounds and a shift in the preferential C source utilized by the microbial community overwinter. This article is protected by copyright. All rights reserved.

Description: Miscanthus is a promising fiber crop with high potential for sustainable biomass production for a biobased economy. The effect of biomass composition on the processing efficiency of miscanthus biomass for different biorefinery value chains was evaluated, including combustion, anaerobic digestion and enzymatic saccharification for the production of bioethanol. Biomass quality and composition was analyzed in detail using stem and leaf fractions of summer (July) and winter (March) harvested biomass of eight compositionally diverse Miscanthus sinensis genotypes. Genotype performance in tests for enzymatic saccharification, anaerobic digestion and combustion differed extensively. The variation between the best and the worst performing genotype was 18% for biogas yield (ml/g dm) and 42% for saccharification efficiency (glucose release as %dm). The ash content of the best performing genotype was 62% lower than that of the genotype with the highest ash content and showed a considerably high ash melting temperature during combustion. Variation between genotypes in biomass quality for the different thermochemical bioconversion processes was shown to be strongly correlated to differences in biomass composition. The most important traits that contributed favorably to biogas yields and saccharification efficiency were a high content of trans -ferulic acid, a high ratio of para -coumaric acid to lignin and a low lignin content. Additionally, a high content of hemicellulosic polysaccharides positively affected saccharification efficiency. Low contents of ash and inorganic elements positively affect biomass quality for combustion and low potassium and chloride contents contributed to a higher ash melting temperature. These results demonstrate the potential for optimizing and exploiting M. sinensis as a multi-purpose lignocellulosic feedstock, particularly for bioenergy applications. This article is protected by copyright. All rights reserved.

Description: Rewetting of drained peatlands has been recommended to reduce CO 2 emissions and to restore the carbon sink function of peatlands. Recently, the combination of rewetting and biomass production (paludiculture) has gained interest as a possible land use option in peatlands for obtaining such benefits of lower CO 2 emissions without losing agricultural land. The present study quantified the carbon balance (CO 2 , CH 4 and harvested biomass C) of rewetted and drained peat soils under intensively managed reed canary grass (RCG) cultivation. Mesocosms were maintained at five different ground water levels (GWL), i.e., 0, 10, 20 cm below the soil surface, representing rewetted peat soils, and 30 and 40 cm below the soil surface, representing drained peat soils. Net ecosystem exchange (NEE) of CO 2 and CH 4 emissions were measured during the growing period of RCG (May to September) using transparent and opaque closed chamber methods. The average dry biomass yield was significantly lower from rewetted peat soils (12 Mg ha −1 ) than drained peat soils (15 Mg ha −1 ). Also, CO 2 fluxes of gross primary production (GPP) and ecosystem respiration (ER) from rewetted peat soils were significantly lower than drained peat soils but net uptake of CO 2 was higher from rewetted peat soils. Cumulative CH 4 emissions were negligible (0.01 g CH 4 m −2 ) from drained peat soils but were significantly higher (4.9 g CH 4 m −2 ) from rewetted peat soils during measurement period (01 May-15 September, 2013). The extrapolated annual C balance was 0.03 and 0.68 kg C m −2 from rewetted and drained peat soils, respectively indicating that rewetting and paludiculture can reduce the loss of carbon from peatlands. This article is protected by copyright. All rights reserved.

Description: We implemented a spatial application of a previously-evaluated model of soil GHG emissions, ECOSSE, in the UK to examine the impacts to 2050 of land use transitions from existing land use: rotational cropland, permanent grassland or woodland, to six bioenergy crops; three “first generation” energy crops: oil seed rape, wheat and sugar beet, and three “second generation” energy crops: Miscanthus , short rotation coppice willow (SRC), and short rotation forestry poplar (SRF). Conversion of rotational crops to Miscanthus , SRC and SRF and conversion of permanent grass to SRF show beneficial changes in soil GHG balance over a significant area. Conversion of permanent grass to Miscanthus , permanent grass to SRF, and forest to SRF show detrimental changes in soil GHG balance over a significant area. Conversion of permanent grass to wheat, oilseed rape, sugar beet and SRC and all conversions from forest show large detrimental changes in soil GHG balance over most of the UK, largely due to moving from uncultivated soil to regular cultivation. Differences in net GHG emissions between climate scenarios to 2050 were not significant. Overall, SRF offers the greatest beneficial impact on soil GHG balance. These results provide one criterion for selection of bioenergy crops and do not consider GHG emission increases/decreases resulting from displaced food production, bio-physical factors (e.g. the energy-density of the crop) and socio-economic factors (e.g. expenditure on harvesting equipment). Given that the soil GHG balance is dominated by change in soil organic carbon (SOC) with the difference among Miscanthus , SRC and SRF largely determined by yield, a target for management of perennial energy crops is to achieve the best possible yield by using the most appropriate energy crop and cultivar for the local situation. This article is protected by copyright. All rights reserved.

Description: Social and economic indicators can be used to support design of sustainable energy systems. Indicators representing categories of social well-being, energy security, external trade, profitability, resource conservation, and social acceptability have yet been measured in published sustainability assessments for commercial algal biofuel facilities. We review socioeconomic indicators that have been modeled at the commercial scale or measured at the pilot or laboratory scale, as well as factors that affect them, and discuss additional indicators that should be measured during commercialization to form a more complete picture of socioeconomic sustainability of algal biofuels. Indicators estimated in the scientific literature include the profitability indicators, return on investment (ROI) and net present value (NPV), and the resource conservation indicator, fossil energy return on investment (EROI). These modeled indicators have clear sustainability targets and have been used to design sustainable algal biofuel systems. Factors affecting ROI, NPV, and EROI include infrastructure, process choices, and financial assumptions. The food security indicator, percent change in food price volatility , is probably zero where agricultural lands are not used for production of algae-based biofuels, however, food-related co-products from algae could enhance food security. The energy security indicators energy security premium and fuel price volatility and external trade indicators terms of trade and trade volume cannot be projected into the future with accuracy prior to commercialization. Together with environmental sustainability indicators, the use of a suite of socio-economic sustainability indicators should contribute to progress toward sustainability of algal biofuels. This article is protected by copyright. All rights reserved.

Description: In this study, we used ELISA for quantification of PPDK in photosynthesizing leaves of miscanthus. We cloned a fragment of the gene encoding PPDK, purified the resulting protein by affinity chromatography, identified it using MALDI mass spectrometry, and obtained monoclonal antibodies by immunizing BALB/c mice. Selectivity of monoclonal antibodies was assessed by Western blot using the protein extracts of Soranovskii. The presence of PPDK was again verified by MALDI mass spectrometry. Therefore, we developed and tested the method for determining PPDK quantity in miscanthus using ELISA. This article is protected by copyright. All rights reserved.

Description: With growing interest in the role of microbiomes, and symbionts in particular, the aim of this study was to determine the diversity of the bacterial endophyte population within Miscanthus and to ascertain the extent of vertical transmission via the seed. A great diversity of endophytic bacteria were found in all parts of the mature plant (rhizome, root, stem and leaf), and in seedlings grown from sterilised seed grown in sterile conditions. A total of 3 phyla and 5 families of bacteria were identified as cultures compared to 19 phyla and 85 families using 16S rDNA amplification and sequencing. Not all cultured bacteria could be identified by 16S rDNA, implying that the true diversity is even greater. More bacterial diversity was identified in sterile-grown seedlings than in all parts of the mature plant combined, 17 and 13 phyla respectively with 11 in common. 5 phyla were present in all plant samples examined. Vertical transmission via the seed may therefore be a major source of endophytes in Miscanthus, presumably supplemented by ingress of soil bacteria as the plant grows. Bacteria identified from the mature plant were predominantly similar to known bacterial sequences in Genbank, but a small number from the stem and many from the seed were novel, potentially adapted to an in planta lifecycle. Endophytic bacteria were found to form spores and other dense structures, and this provides a mechanism for long term survival and seed transmission. The staining of germinating seeds identified bacteria at the root tip of the emerging radicle. We propose that seed transmission of bacterial endophytes requires adaptation of both plant and microbes, plays a role in germination and has evolutionary significance and implications for future plant breeding approaches, in Miscanthus and more widely. This article is protected by copyright. All rights reserved.

Description: GCB Bioenergy, Volume 11, Issue 8, Page 911-913, August 2019.

Description: Abstract The use of land resources has a strong influence on the sustainability of biofuel production. An assessment of both direct and indirect changes in land use is necessary if an accurate assessment of sustainability is to be made. An increasing number of studies have developed approaches to estimate the indirect land use change (ILUC) impacts of biofuels at global, national or regional level, but assessing ILUC remains a challenging task and estimates vary widely. In this study, we suggest that a socially‐motivated, project level approach can provide robust insight into the conditions affecting land use change dynamics. We developed a causal‐descriptive approach named ILUC Project ASsessment Tool (ILUC PAST) for project level assessment of ILUC. It uses a tiered multi‐tool analysis – from local to global – combined with extensive stakeholder engagement. A real‐world project for the production of cellulosic ethanol in Sardinia (Italy) was used to evaluate the tool and benchmark the results against two alternatives for project level assessment: the ‘Low Indirect Impact Biofuel' methodology and the ‘iLUC Club' method. The results of the case study of advanced biofuels suggest that the quantitative estimates of ILUC combined with the in‐depth understanding of the cause‐and‐effect dynamics provided by ILUC PAST are sufficiently credible, salient and legitimate to support project‐level and local decision making. This article is protected by copyright. All rights reserved.

Description: Abstract In recent years, production of pellets derived from forestry biomass to replace coal for electricity generation has been increasing, with over 10 million tonnes traded internationally‐ primarily between USA and Europe but with an increasing trend to Asia. Critical to this trade is the classification of woody biomass as ‘renewable energy' and thus eligible for public subsidies. However, much scientific study on the net effect of this trend suggest that it is having the opposite effect to that expected of renewable energy, by increasing atmospheric levels of carbon dioxide for substantial periods of time. This review, based on recent work by Europe's Academies of Science, finds that current policies are failing to recognise that removing forest carbon stocks for bioenergy leads to an initial increase in emissions. Moreover, that the periods during which atmospheric CO2 levels are raised before forest regrowth can reabsorb the excess emissions are incompatible with the urgency of reducing emissions to comply with the objectives enshrined in the Paris Agreement. We consider how current policy might be reformed to reduce negative impacts on climate and argue for a more realistic science‐based assessment of the potential of forest bioenergy in substituting for fossil fuels. The length of time atmospheric concentrations of CO2 increase is highly dependent on the feedstocks and we argue for regulations to explicitly require these to be sources with short payback periods. Furthermore, we describe the current UNFCCC accounting rules which allow imported biomass to be treated as zero emissions at the point of combustion. and urge their revision to remove the risk of these providing incentives to import biomass with negative climate impacts. Reforms such as these would allow the industry to evolve to methods and scales which are more compatible with the basic purpose for which it was designed. This article is protected by copyright. All rights reserved.

Description: GCB Bioenergy, Volume 11, Issue 9, Page 1009-1011, September 2019.

Description: GCB Bioenergy, Volume 11, Issue 10, Page 1099-1101, October 2019.

Description: Abstract Technologies for upgrading fast pyrolysis bio‐oil to drop‐in fuels and co‐products are under development and show promise for decarbonizing energy supply for transportation and chemicals markets. The successful commercialization of these fuels and the technologies deployed to produce them depend on production costs, scalability, and yield. To meet environmental regulations, pyrolysis‐based biofuels need to adhere to life cycle greenhouse gas (GHG) intensity standards relative to their petroleum‐based counterparts. We review literature on fast pyrolysis bio‐oil upgrading and explore key metrics that influence their commercial viability through life cycle assessment (LCA) and techno‐economic analysis (TEA) methods together with technology readiness level (TRL) evaluation. We investigate the tradeoffs among economic, environmental and technological metrics derived from these methods for individual technologies as a means of understanding their nearness to commercialization. Although the technologies reviewed have not attained commercial investment, some have been pilot‐tested. Predicting the projected performance at scale‐up through models can, with industrial experience, guide decision‐making to competitively meet energy policy goals. LCA and TEA methods that ensure consistent and reproducible models at a given TRL are needed to compare alternative technologies. This study highlights the importance of integrated analysis of multiple economic, environmental and technological metrics for understanding performance prospects and barriers among early stage technologies.

Description: GCB Bioenergy, Volume 11, Issue 11, Page 1253-1255, November 2019.

Description: GCB Bioenergy, Volume 11, Issue 4, Page 551-553, April 2019.

Description: In this paper, we focus on the impact on soil organic carbon (SOC) of two dedicated energy crops: perennial grass Miscanthus x Giganteus ( Miscanthus ) and short rotation coppice (SRC)-willow. The amount of SOC sequestered in the soil is a function of site-specific factors including soil texture, management practices, initial SOC levels, and climate; for these reasons both losses and gains in SOC were observed in previous Miscanthus and SRC-willow studies. The ECOSSE model was developed to simulate soil C dynamics and greenhouse gas (GHG) emissions in mineral and organic soils. The performance of ECOSSE has already been tested at site level to simulate the impacts of land-use change to short rotation forestry (SRF) on SOC. However, it has not been extensively evaluated under other bioenergy plantations, such as Miscanthus and SRC-willow. Twenty-nine locations in the UK, comprising 19 paired transitions to SRC-willow and 20 paired transitions to Miscanthus , were selected to evaluate the performance of ECOSSE in predicting SOC and SOC change from conventional systems (arable and grassland) to these selected bioenergy crops. The results of the present work revealed a strong correlation between modelled and measured SOC and SOC change after transition to Miscanthus and SRC-willow plantations, at two soil depths (0-30 cm and 0-100 cm), as well as the absence of significant bias in the model. Moreover, model error was within (i.e. not significantly larger than) the measurement error. The high degrees of association and coincidence with measured SOC under Miscanthus and SRC-willow plantations in UK, provides confidence in using this process-based model for quantitatively predicting the impacts of future land-use on SOC, at site level as well as at national level. This article is protected by copyright. All rights reserved.

Description: Small-scale Jatropha cultivation and biodiesel production has the potential of contributing to local development, energy security and greenhouse gas (GHG) mitigation. In recent years however, the GHG mitigation potential of biofuel crops is heavily disputed due to the occurrence of a carbon debt, caused by CO 2 emissions from biomass and soil after land use change (LUC). Most published carbon footprint studies of Jatropha report modeled results based on a very limited database. In particular, little empirical data exist on the effects of Jatropha on biomass and soil C stocks. In this study we used field data to quantify these C pools in three land uses in Mali, i.e. Jatropha plantations, annual cropland and fallow land, to estimate both the Jatropha C debt and its C sequestration potential. Four years old Jatropha plantations hold on average 2.3 Mg C ha −1 in their above- and belowground woody biomass, which is considerably lower compared to results from other regions. This can be explained by the adverse growing conditions and poor local management. No significant soil organic carbon (SOC) sequestration could be demonstrated after four years of cultivation. While the conversion of cropland to Jatropha does not entail significant C losses, the replacement of fallow land results in an average C debt of 34.7 Mg C ha −1 , mainly caused by biomass removal (73%). Retaining native savannah woodland trees on the field during LUC and improved crop management focusing on SOC conservation can play an important role in reducing Jatropha's C debt. Although planting Jatropha on degraded, carbon-poor cropland results in a limited C debt, the low biomass production and seed yield attained on these lands reduce Jatropha's potential to sequester C and replace fossil fuels. Therefore, future research should mainly focus on increasing Jatropha's crop productivity in these degraded lands. This article is protected by copyright. All rights reserved.

Description: This paper investigates the dynamic linkages between biofuels production and sustainable indicators in the panel of 17 developed and developing countries, over the period of 2000-2012. The study emphasized the role of biofuels production in the sustainable development of the region. For this purpose, the study utilized four main sustainable indicators including carbon dioxide emissions, energy intensity, renewable energy generation and total population that have a significant impact on the biofuels production. The study used dynamic heterogeneous panel econometric technique – Generalized Method of Moments and found that carbon dioxide emissions increase along with the increase in biofuels production. Therefore, the caution should be applied when burning the biofuels during the production process. In addition, renewable electricity generation also increases the biofuels production in the region. The results of robust least square regression confirmed that all of the sustainable indicators have a significant association with the biofuels production, as total primary energy consumption increases the biofuels production while total population significantly decreases the biofuels production in the region. The results derived to the conclusion that for sustainable development in the region, the policy makers should have to formulate carbon free policies that coupled with the renewable energy sources for emphasizing the life-cycle of bioenergy during the production process. This article is protected by copyright. All rights reserved.

Description: In the UK and other temperate regions Short Rotation Coppice (SRC) and Miscanthus x giganteus ( Miscanthus ) are two of the leading “second-generation” bioenergy crops. Grown specifically as a low carbon (C) fossil fuel replacement, calculations of the climate mitigation provided by these bioenergy crops rely on accurate data. There are concerns that uncertainty about impacts on soil C stocks of transitions from current agricultural land use to these bioenergy crops could lead to either an under- or over-estimate of their climate mitigation potential. Here, for locations across mainland Great Britain (GB), a paired-site approach and a combination of 30 cm and 1 m deep soil sampling were used to quantify impacts of bioenergy land-use transitions on soil C stocks in 41 commercial land use transitions; 12 arable to SRC, 9 grassland to SRC, 11 arable to Miscanthus and 9 grassland to Miscanthus . Mean soil C stocks were lower under both bioenergy crops than under the grassland controls but only significantly at 0-30 cm. Mean soil C stocks at 0-30 cm were 33.55 ± 7.52 Mg C ha −1 and 26.83 ± 8.08 Mg C ha −1 lower under SRC (p = 0.004) and Miscanthus plantations (p = 0.001), respectively. Differences between bioenergy crops and arable controls were not significant in either the 30 cm or 1 m soil cores and smaller than for transitions from grassland. No correlation was detected between change in soil C stock and bioenergy crop age (time since establishment) or soil texture. Change in soil C stock was, however, negatively correlated with the soil C stock in the original land use. We suggest, therefore, that selection of sites for bioenergy crop establishment with lower soil C stocks, most often under arable land use, are the most likely to result in increased soil C stocks. This article is protected by copyright. All rights reserved.

Description: Understanding genotype × environment interaction (GEI) is crucial to optimize the deployment of clonal material to field conditions in short rotation coppice poplar plantations. Hybrid poplars are grown for biomass production under a wide range of climatic and edaphic conditions, but their adaptive performance in Mediterranean areas remains poorly characterized. In this work, site regression (SREG) and factorial regression mixed models are combined to gain insight into the nature and causes underlying GEI for biomass production of hybrid poplar clones. SREG addresses the issue of clonal recommendation in multi-environment trials (MET) through a biplot representation that visually identifies superior genotypes. Factorial regression, alternatively, involves a description of clonal reaction to the environment in terms of physical variables that directly affect productivity. Initially, SREG aided at identifying cross-over interactions that often involved hybrids of different taxonomic background. Factorial regression then selected latitude, mean temperature of the vegetative period (MTVP) and soil sand content as main site factors responsible for differential clonal adaptation. Genotypic responses depended strongly on taxonomic background: P. deltoides Bartr. ex Marsh. × P. nigra L. clones showed an overall positive sensitivity to increased MTVP and negative sensitivity to increased sand content, whereas the opposite occurred for P. trichocarpa Torr. & Gray × P. deltoides clones; the three-cross hybrid [( P. deltoides × P. trichocarpa ) × P. nigra ] often displayed an intermediate performance. This information can contribute towards the identification and biological understanding of adaptive characteristics relevant for poplar breeding in Mediterranean conditions and facilitate clonal recommendation at eco-regional level. This article is protected by copyright. All rights reserved.

Description: We developed a biochar model within the Agricultural Production Systems sIMulator (APSIM) software that integrates biochar knowledge and enables simulation of biochar effects within cropping systems. The model has algorithms that mechanistically connect biochar to soil organic carbon (SOC), soil water, bulk density (BD), pH, cation exchange capacity, and organic and mineral nitrogen. Soil moisture–temperature–nitrogen limitations on the rate of biochar decomposition were included as well as biochar-induced priming effect on SOC mineralization. The model has 10 parameters that capture the diversity of biochar types, 15 parameters that address biochar-soil interactions and 4 constants. The range of values and their sensitivity is reported. The biochar model was connected to APSIM's maize and wheat crop models to investigate long-term (30 years) biochar effects on US maize and Australia wheat in various soils. Results from this sensitivity analysis showed that the effect of biochar was the largest in a sandy soil (Australian wheat) and the smallest in clay loam soil (US maize). On average across cropping systems and soils the order of sensitivity and the magnitude of the response of biochar to various soil-plant processes was (from high to low): SOC (11 to 86%) 〉 N 2 O emissions (–10 to 43%) 〉 plant available water content (0.6 to 12.9%) 〉 BD (–6.5 to –1.7%) 〉 pH (–0.8 to 6.3%) 〉 net N mineralization (–19 to 10%) 〉 CO 2 emissions (–2.0 to 4.3%) 〉 water filled pore space (–3.7 to 3.4%) 〉 grain yield (–3.3 to 1.8%) 〉 biomass (–1.6 to 1.4%). Our analysis showed that biochar has a larger impact on environmental outcomes rather than agricultural production. The mechanistic model has the potential to optimize biochar application strategies to enhance environmental and agronomic outcomes but more work is needed to fill knowledge gaps identified in this work. This article is protected by copyright. All rights reserved.

Description: Biorefining agro-industrial biomass residues for bioenergy production represents an opportunity for both sustainable energy supply and greenhouse gas (GHG) emissions mitigation. Yet, is bioenergy the most sustainable use for these residues? To assess the importance of the alternative use of these residues, a consequential life-cycle assessment (LCA) of 32 energy-focused biorefinery scenarios was performed based on eight selected agro-industrial residues and four conversion pathways (two involving bioethanol and two biogas). To specifically address indirect land-use changes (iLUC) induced by the competing feed/food sector, a deterministic iLUC model, addressing global impacts, was developed. A dedicated biochemical model was developed to establish detailed mass, energy, and substance balances for each biomass conversion pathway, as input to the LCA. The results demonstrated that even for residual biomass, environmental savings from fossil fuel displacement can be completely out-balanced by iLUC, depending on the feed value of the biomass residues. This was the case of industrial residues brewer's grain, beet residues, potato pulp, and whey. Overall, the GHGs from iLUC impacts were quantified to 4.1 t CO 2 -eq.ha -1 demanded y -1 corresponding to 1.2-1.5 t CO 2 t -1 dry biomass used for energy. Only bioenergy from straw and wild grass was shown to perform better than the alternative use, as no competition with the feed sector was involved. Biogas for heat-and-power production was the best performing pathway, in a short-term context. Focusing on transport fuels, bioethanol was generally preferable to biomethane considering conventional biogas upgrading technologies. Based on the results, agro-industrial residues cannot be considered burden-free simply because they are a residual biomass and careful accounting of alternative utilization is a pre-requisite to assess the sustainability of a given use. In this endeavor, the iLUC factors and biochemical model proposed herein can be used as templates and directly applied to any bioenergy consequential study involving demand for arable land. This article is protected by copyright. All rights reserved.

Description: China has developed ambitious bioenergy installation targets as part of its broader goals to increase its renewable energy generating capacity and decarbonise its economy. A key target feedstock for bioenergy is the 800 million tonnes of agricultural residues that China produces each year. At present the main financial incentive to support bioenergy generation from agricultural residues is a feed-in-tariff provided for bioenergy that is produced by units that take 80% or more of their feedstock energy from biomass. Although this policy has catalysed the construction of many bioenergy units, there are reports that these projects are experiencing serious financial and technical problems, leading to low operational efficiency and even closure. An alternative option for China's agricultural residues is cofiring with coal in existing power stations. However this is currently unprofitable for power station operators, as cofiring is not eligible for financial assistance through the bioenergy feed-in-tariff. In light of China's ambitious target to install 30GW of bioenergy generation capacity by 2020, this paper investigates the extent to which extension of the bioenergy feed-in-tariff to include cofiring could contribute towards this goal. The results suggest that 39% of China's straw energy resources are located within 50km of a powerstation. Assuming cofiring ratios of up to 10% coal energy replacement, an annual 89-117TWh of electricity could be generated by cofiring agricultural residues collected within 50km radii of powerstations. If China extends its bioenergy subsidies to include cofiring, an annual 62-92TWh can be produced at an internal rate of return of 8% or more. This equates to 42-62% of the bioenergy generation that China might expect if it met its 2020 target of installing 30GW of bioenergy capacity. Overall this indicates a strong case for the Chinese government to extend its existing bioenergy feed-in-tariff to include cofiring at low energy replacement ratios. This article is protected by copyright. All rights reserved.

Description: The environmental benefits of a broad scale adoption of biofuels are critically contingent on what current land uses will be converted for feedstock expansion and how converted land will be managed. We assessed the consequences of land use and land management for the agroindustrial production of sugarcane to the physical, chemical and biological properties of freshwater systems. We surveyed 16 environmental variables and algae, tadpoles, predatory invertebrates and fish in lentic water bodies distributed across a gradient in land use intensity ranging from seasonal Atlantic Forest and cerrado to pastures to sugarcane plantations in SE Brazil, the most important sugarcane-producing region in the world. The gradient in land use intensity was not only an axis of native habitat loss but also of ecosystem productivity, as indicated by increased conductivity, turbidity, and phytoplankton biomass. Land use had a clear signal on community and metacommunity organization, with converted land being impoverished in biodiversity relative to native habitats. However, frequency of occurrence, density, biomass and alpha diversity of tadpoles and their predators were not affected by land use. These results suggest that sugarcane fields function as habitat to a fraction of aquatic biodiversity. Within sugarcane fields, larger wetlands surrounded by buffer strips as required by law appeared comparatively buffered against land management practices and housed a disproportional fraction of animal biomass, likely acting as sources of migrants to other water bodies in the landscape. Conversion of pastures to sugarcane fields, suggested as a strategy to reduce competition for land with food production and biodiversity conservation, does not appear to have strong consequences to lentic freshwater systems, provided that wetlands and surrounding buffer strips are preserved. These observations emphasize the importance of enforcement of legislation regulating land use (i.e. the ′Forest Code′) and certification systems rewarding the voluntary adoption of better land management practices. This article is protected by copyright. All rights reserved.

Description: Miscanthus lutarioriparius is an endemic species that grows along the middle and lower reaches of the Yangtze River and is a valuable source of germplasm for the development of second-generation energy crops. The plant that propagates via seeds, stem nodes, and rhizomes shows high phenotypic variation and strong local adaptation. Here, we examined the magnitude and spatial distribution of genetic variation of M. lutarioriparius across its entire distributional range and tested underlying factors that shaped its genetic variation. Population genetic analyses were conducted on 644 individuals from 25 populations using 16 microsatellite markers. M. lutarioriparius exhibited a high level of genetic variation ( H E = 0.682-0.786; A r = 4.74-8.06) and a low differentiation ( F ST = 0.063; D est = 0.153). Of the total genetic variation, 10% was attributed to differences among populations ( d.f . = 24, P 〈 0.0001), whereas 90% was attributed to the differences among individuals ( d.f . = 619, P 〈= 0.0001). Genetic diversity did not differ significantly across longitudes and did not increase in the populations growing downstream of the Yangtze River. However, significant associations were found between genetic differentiation and spatial distance. Six genetic discontinuities were identified, which mostly distributed among downstream populations. We conclude that anthropogenic factors and landscape features both contributed to shaping the pattern of gene flow in M. lutarioriparius , including long-distance bidirectional dispersal. Our results explain the genetic basis of the high degree of adaptability in M. lutarioriparius and identify potential sources of new germplasm for the domestication of this potential second-generation energy crop. This article is protected by copyright. All rights reserved.

Description: Locally produced bioenergy can decrease the dependency on imported fossil fuels in a region, while also being valuable for climate change mitigation. Short-rotation coppice willow is a potentially high-yielding energy crop that can be grown to supply a local energy facility. This study assessed the energy performance and climate impacts when establishing willow on current fallow land in a Swedish region with the purpose of supplying a bio-based combined heat and power plant. Time-dependent life cycle assessment (LCA) was combined with GIS mapping to include spatial variation in terms of transport distance, initial soil organic carbon content, soil texture and yield. Two climate metrics were used (global warming potential (GWP) and absolute global temperature change potential (AGTP)), and the energy performance was determined by calculating the energy ratio (energy produced per unit of energy used). The results showed that when current fallow land in a Swedish region was used for willow energy, an average energy ratio of 30 MJ MJ −1 (including heat, power and flue gas condensation) was obtained and on average 84.3 Mg carbon per ha was sequestered in the soil during a 100 year time frame (compared with the reference land use). The processes contributing most to the energy use during one willow rotation was the production and application of fertilisers (~40%), followed by harvest (~35%) and transport (~20%). The temperature response after 100 years of willow cultivation was -6·10 -16 K MJ −1 heat, which is much lower compared with fossil coal and natural gas (70·10 -16 K MJ −1 heat and 35·10 -16 K MJ −1 heat, respectively). The combined GIS and time-dependent LCA approach developed here can be a useful tool in systematic analysis of bioenergy production systems and related land use effects. This article is protected by copyright. All rights reserved.

Description: Reliance on fossil fuels is causing unprecedented climate change and is accelerating environmental degradation and global biodiversity loss. Together, climate change and biodiversity loss, if not averted urgently, may inflict severe damage on ecosystem processes, functions and services that support the welfare of modern societies. Increasing renewable energy deployment and expanding the current protected area network represent key solutions to these challenges, but conflicts may arise over the use of limited land for energy production as opposed to biodiversity conservation. Here, we compare recently identified core areas for the expansion of the global protected area network with the renewable energy potential available from land-based solar photovoltaic, wind energy and bioenergy (in the form of Miscanthus × giganteus ). We show that these energy sources have very different biodiversity impacts and net energy contributions. The extent of risks and opportunities deriving from renewable energy development is highly dependent on the type of renewable source harvested, the restrictions imposed on energy harvest and the region considered, with Central America appearing at particularly high potential risk from renewable energy expansion. Without restrictions on power generation due to factors such as production and transport costs, we show that bioenergy production is a major potential threat to biodiversity, while the potential impact of wind and solar appears smaller than that of bioenergy. However, these differences become reduced when energy potential is restricted by external factors including local energy demand. Overall, we found that areas of opportunity for developing solar and wind energy with little harm to biodiversity could exist in several regions of the world, with the magnitude of potential impact being particularly dependent on restrictions imposed by local energy demand. The evidence provided here helps guide sustainable development of renewable energy and contributes to the targeting of global efforts in climate mitigation and biodiversity conservation.

Description: Belowground root biomass is infrequently measured and simply represented in models that predict landscape-level changes to soil carbon stocks and greenhouse gas balances. Yet, crop-specific responses to N fertilizer and harvest treatments are known to impact both plant allocation and tissue chemistry, potentially altering decomposition rates and the direction and magnitude of soil C stock changes and greenhouse gas fluxes. We examined switchgrass ( Panicum virgatum L.) and corn ( Zea mays L.,) yields, belowground root biomass, C, N and soil particulate organic matter–C (POM-C) in a 9-year rainfed study of N fertilizer rate (0, 60, 120, and 180 kg N ha −1 ) and harvest management near Mead, NE USA. Switchgrass was harvested with one pass in either August or post-frost and for no-till (NT) corn either 50% or no stover was removed. Switchgrass had greater belowground root biomass C & N (6.39, 0.10 Mg ha −1 ) throughout the soil profile compared to NT-corn (1.30, 0.06 Mg ha −1 ) and a higher belowground root biomass C:N ratio, indicating greater recalcitrant belowground root biomass C input beneath switchgrass. There was little difference between the two crops in soil POM-C indicating substantially slower decomposition and incorporation into SOC under switchgrass, despite much greater root C. The highest N rate decreased POM-C under both NT-corn and switchgrass, indicating faster decomposition rates with added fertilizer. Residue removal reduced corn belowground root biomass C by 37% and N by 48% and subsequently reduced POM-C by 22% compared to no residue removal. Developing productive bioenergy systems that also conserve the soil resource will require balancing fertilization that maximizes aboveground productivity but potentially reduces SOC sequestration by reducing belowground root biomass and increasing root and soil C decomposition. This article is protected by copyright. All rights reserved.

Description: Accurately assessing the delay before the substitution of fossil fuel by forest bioenergy starts having a net beneficial impact on atmospheric CO 2 is becoming important as the cost of delaying GHG emission reductions is increasingly being recognised. We documented the time to carbon (C) parity of forest bioenergy sourced from different feedstocks (harvest residues, salvaged trees and green trees), typical of forest biomass production in Canada, used to replace three fossil fuel types (coal, oil and natural gas) in heating or power generation. The time to C parity is defined as the time needed for the newly-established bioenergy system to reach the cumulative C emissions of a fossil fuel, counterfactual system. Furthermore, we estimated an uncertainty period derived from the difference in C parity time between predefined best- and worst-case scenarios, in which parameter values related to the supply chain and forest dynamics varied. The results indicate short-to-long ranking of C parity times for residues〈salvaged trees〈green trees and for substituting the less energy-dense fossil fuels (coal〈oil〈natural gas). A sensitivity analysis indicated that silviculture and enhanced conversion efficiency, when occurring only in the bioenergy system, help reduce time to C parity. The uncertainty around the estimate of C parity time is generally small and inconsequential in the case of harvest residues but is generally large for the other feedstocks, indicating that meeting specific C parity time using feedstock other than residues is possible, but would require very specific conditions. Overall, the use of single parity time values to evaluate the performance of a particular feedstock in mitigating GHG emissions should be questioned given the importance of uncertainty as an inherent component of any bioenergy project. This article is protected by copyright. All rights reserved.

Description: Perennial grass mixtures planted on Conservation Reserve Program (CRP) land are a potential source of dedicated bioenergy feedstock. Long-term nitrogen (N) and harvest management are critical factors for maximizing biomass yield while maintaining the longevity of grass stands. A six-year farm-scale study was conducted to understand the impact of weather variability on biomass yield, determine optimal N fertilization and harvest timing management practices for sustainable biomass production, and estimate economic viability at six CRP sites in the U.S. Precipitation during the growing season was a critical factor for annual biomass production across all regions, and annual biomass production was severely reduced when growing season precipitation was below 50% of average. The N rate of 112 kg ha −1 produced the highest biomass yield at each location. Harvest timing resulting in the highest biomass yield was site-specific and was a factor of predominant grass type, seasonal precipitation, and the number of harvests taken per year. The use of N fertilizer for yield enhancement unambiguously increased the cost of biomass regardless of the harvest timing for all six sites. The breakeven price of biomass at the farmgate ranged from $37 to $311 Mg −1 depending on the rate of N application, timing of harvesting and location when foregone opportunity costs were not considered. Breakeven prices ranged from $69 to $526 Mg −1 when the loss of CRP land rental payments were included as opportunity costs. Annual cost of the CRP to the federal government could be reduced by over 8% in the states included in this study; however, this would require the biomass price to be much higher than in the case where the landowner receives the CRP land rent. This field research demonstrated the importance of long-term, farm-scale research for accurate estimation of biomass feedstock production and economic viability from perennial grasslands. This article is protected by copyright. All rights reserved.

Description: Perennial grasses can sequester soil organic carbon (SOC) in sustainably managed biofuel systems, directly mitigating atmospheric CO 2 concentrations while simultaneously generating biomass for renewable energy. The objective of this study was to quantify SOC accumulation and identify the primary drivers of belowground C dynamics in a zero-tillage production system of tropical perennial C4 grasses grown for biofuel feedstock in Hawaii. Specifically, the quantity, quality, and fate of soil C inputs were determined for eight grass accessions – four varieties each of napiergrass and Guinea grass. Carbon fluxes (soil CO 2  efflux, aboveground net primary productivity, litterfall, total belowground carbon flux, root decay constant), C pools (SOC pool and root biomass), and C quality (root chemistry, C and nitrogen concentrations, and ratios) were measured through three harvest cycles following conversion of a fallow field to cultivated perennial grasses. A wide range of SOC accumulation occurred, with both significant species and accession effects. Aboveground biomass yield was greater and root lignin concentration was lower for napiergrass than Guinea grass. Structural equation modeling revealed that root lignin concentration was the most important driver of SOC pool: varieties with low root lignin concentration, which was significantly related to rapid root decomposition, accumulated the greatest amount of SOC. Roots with low lignin concentration decomposed rapidly, but the residue and associated microbial biomass/byproducts accumulated as SOC. In general, napiergrass was better suited for promoting soil C sequestration in this system. Further, high yielding varieties with low root lignin concentration provided the greatest climate change mitigation potential in a ratoon system. Understanding the factors affecting SOC accumulation and the net greenhouse gas tradeoffs within a biofuel production system will aid in crop selection to meet multiple goals towards environmental and economic sustainability. This article is protected by copyright. All rights reserved.

Description: Understanding the complex interactions among food security, bioenergy sustainability, and resource management requires a focus on specific contextual problems and opportunities. The United Nations’ 2030 Sustainable Development Goals place a high priority on food and energy security; bioenergy plays an important role in achieving both goals. Effective food security programs begin by clearly defining the problem and asking, ‘What can be done to assist people at high risk?’ Simplistic global analyses, headlines, and cartoons that blame biofuels for food insecurity may reflect good intentions but mislead the public and policymakers because they obscure the main drivers of local food insecurity and ignore opportunities for bioenergy to contribute to solutions. Applying sustainability guidelines to bioenergy will help achieve near- and long-term goals to eradicate hunger. Priorities for achieving successful synergies between bioenergy and food security include the following: (1) clarifying communications with clear and consistent terms, (2) recognizing that food and bioenergy need not compete for land and, instead, should be integrated to improve resource management, (3) investing in technology, rural extension, and innovations to build capacity and infrastructure, (4) promoting stable prices that incentivize local production, (5) adopting flex crops that can provide food along with other products and services to society, and (6) engaging stakeholders to identify and assess specific opportunities for biofuels to improve food security. Systematic monitoring and analysis to support adaptive management and continual improvement are essential elements to build synergies and help society equitably meet growing demands for both food and energy.

Description: A life-cycle assessment (LCA) of a low-input, short rotation coppice (SRC) willow grown on different Danish lands was performed. Woodchips are gasified, producer gas is used for co-generation of heat and power (CHP) and the ash-char output is applied as soil amendment in the field. A hybrid model was developed for the estimation of greenhouse gas (GHG) emissions from indirect land-use changes (iLUC) induced by willow cropping on arable land. For this, area expansion results from a general equilibrium economic model were combined with global LUC trends to differentiate between land transformation (as additional agricultural expansion, in areas with historical deforestation) and occupation (as delayed relaxation, DR, in areas with historical land abandonment) impacts. A biophysical approach was followed to determine the iLUC feed emissions factor from marginal grassland. Land transformation impacts were derived from latest world deforestation statistics, while a commercial feed mix of equivalent nutritive value was assumed to substitute the displaced grass as fodder. Intensification effects were included in both iLUC factors as additional N-fertilizer consumption. Finally, DR impacts were considered for abandoned farmland, as a relative C stock loss compared to natural regeneration. ILUC results show that area related GHG emissions are dominant (93% of iLUC food and 80% of iLUC feed ), transformation being more important (82% of iLUC food ) than occupation (11%) impacts. LCA results show that CHP from willow emits 4,047 kg CO 2 -eq ha occup −1 (or 0.8 gCO 2 -eq MJ −1 ) when grown on arable land, while sequestering 43,745 kg CO 2 -eq ha occup −1 (or -10.4 gCO 2 -eq MJ −1 ) when planted on marginal pastureland, and 134,296 kg CO 2 -eq ha occup −1 (or -31.8 gCO 2 -eq MJ −1 ) when marginal abandoned land is cultivated. Increasing the bioenergy potential without undesirable iLUC effects, especially relevant regarding biodiversity impacts, requires that part of the marginally used extensive grasslands are released from their current use or energy cropping on abandoned farmland incentivized. This article is protected by copyright. All rights reserved.

Description: Biochar application to soils may increase carbon (C) sequestration due to the inputs of recalcitrant organic C. However, the effects of biochar application on the soil greenhouse gases (GHGs) fluxes appear variable among many case studies; therefore the efficacy of biochar as a carbon sequestration agent for climate change mitigation remains uncertain. We performed a meta-analysis of 91 published papers with 552 paired comparisons to obtain a central tendency of three main GHG fluxes (i.e., CO 2 , CH 4 , and N 2 O) in response to biochar application. Our results showed that biochar application significantly increased soil CO 2 fluxes by 22.14%, but decreased N 2 O fluxes by 30.92% and did not affect CH 4 fluxes. As a consequence, biochar application may significantly contribute to increased global warming potential (GWP) of total soil GHG fluxes due to the large stimulation of CO 2 fluxes. However, soil CO 2 fluxes were suppressed when biochar was added to fertilized soils, indicating that biochar application is unlikely to stimulate CO 2 fluxes in the agriculture sector, in which N fertilizer inputs are common. Responses of soil GHG fluxes mainly varied with biochar feedstock source and soil texture, and the pyrolysis temperature of biochar. Soil and biochar pH, biochar applied rate and latitude also influence soil GHG fluxes, but to a more limited extent. Our findings provide a scientific basis for developing more rational strategies towards widespread adoption of biochar as a soil amendment for climate change mitigation. This article is protected by copyright. All rights reserved.

Description: Lignocellulosic biomass is a candidate for future renewable energy resources. Choice of optimum biomass types and biological conversion techniques requires well-founded assessment of the digestibility determining the conversion efficiency. The aim of the present study was to investigate and evaluate the digestibility of miscanthus samples that were tested using three methods: 3,5-dinitrosalicylic acid assay (DNS), anaerobic batch digestion test, and high-throughput pretreatment and hydrolysis method, including a grinding and hydrothermal pretreatment prior to the analysis (HTPH). The miscanthus samples were expected to have different digestibilities due to maturity stage, dry matter content and the implementation of extrusion as a mechanical pretreatment. The results of the DNS and the biogas batch test methods were highly correlated (R 2 between 0.75 and 0.92), but not with the results of the HTPH method. The DNS and biogas batch test showed that digestibility differed between samples, probably due to the degree of lignification and content of soluble sugars. For the HTPH method the digestibility for biorefining was the same irrespective of the variation in the other analyses. The HTPH method had higher biomass use efficiency, closely followed by the biogas batch test running for 91 days on the mechanically pretreated biomass. The HTPH method provided information on the overall quantity of carbohydrates that can be made available from a given biomass. Additionally DNS and biogas batch test visualises the variation in digestibility between biomass types caused by lignification and particle. The study concludes that the choice of evaluation method for miscanthus will depend on the bioenergy conversion method used and that important information on the interaction between physio-chemical pretreatment and biological accessibility of the biomass can be obtained by comparing the methods. This information will enable sound decisions on the future choice of bioenergy conversion technologies. This article is protected by copyright. All rights reserved.