ALBERT

Description: The flowering of sugarcane ( Saccharum spp. hybrids) is a developmental stage that is desirable for breeding programs but undesirable for commercial cultivation, since it causes losses in sugar content and cane yield. This study aimed to (1) characterise the flowering of four varieties of sugarcane with different flowering times and intensities, (2) determine the nutrient levels in their vegetative apexes and (3) to evaluate the effect of calcium on their flowering. The study was divided into two trials. In the first trial, we tested the effect of planting season on the flowering of four varieties of sugarcane that had contrasting flowering periods. Late or reluctant flowering varieties had higher concentrations of calcium in their vegetative apexes in relation to the early variety. At the same time, the early variety, with heavy flowering, had higher potassium in its vegetative apexes. In the second trial, the effect of calcium on their flowering was tested. The application of calcium on the leaves resulted in its accumulation in the vegetative apexes, causing a reduction in potassium levels in the same tissue. This changed the plant phenology, resulting in a month’s delay in flowering and a 50 % reduction in the final flowering intensity. Calcium application by foliar sprays can be used to delay and reduce sugarcane flowering.

Description: A biorefinery may produce multiple fuels from more than one feedstock. The ability of these fuels to qualify as one of the four types of biofuels under the US Renewable Fuel Standard and to achieve a low carbon intensity score under California’s Low Carbon Fuel Standard can be strongly influenced by the approach taken to their life cycle analysis (LCA). For example, in facilities that may co-produce corn grain and corn stover ethanol, the ethanol production processes can share the combined heat and power (CHP) that is produced from the lignin and liquid residues from stover ethanol production. We examine different LCA approaches to corn grain and stover ethanol production considering different approaches to CHP treatment. In the baseline scenario, CHP meets the energy demands of stover ethanol production first, with additional heat and electricity generated sent to grain ethanol production. The resulting greenhouse gas (GHG) emissions for grain and stover ethanol are 57 and 25 g-CO 2 eq/MJ, respectively, corresponding to a 40 and 74 % reduction compared to the GHG emissions of gasoline. We illustrate that emissions depend on allocation of burdens of CHP production and corn farming, along with the facility capacities. Co-product handling techniques can strongly influence LCA results and should therefore be transparently documented.

Description: There is increasing interest in using poplar plantations as sources of bioenergy in many countries, but optimizing their management, robust models for estimating and monitoring their structure, growth and biomass are required. The presented study explores the diameter–height relationships of poplars in 40 plantations on agricultural land located in central and southern Sweden, in order to provide tools for an easy estimation of standing biomass of poplar stands. Diameter and height measurements of 167 trees were included: 117 for calibration and 50 for validation. The constructed diameter–height equations were developed using a mixed-effect modelling approach to address the variations among sites of the plantations and obtain a flexible tool capable of providing locally calibrated estimates. Different models with various structures and stand variables, such as mean diameter and age, were tested. The best model presented R 2 values of 0.87 and 0.96, for the fixed and mixed model parts, respectively. Thus, it appears to be capable of providing useful estimates of heights of poplar stands from measurements of stem diameters in sample plots, thereby facilitating the planning and management of Swedish poplar plantations as future energy feedstock.

Description: How representative are yields from experimental plots compared to large-scale commercial implementation? This study analyses the yields of fast-growing willow plantations for energy reported in experimental trials in Sweden during the period 1980–2012 compared with those from commercial willow plantations for the period 1986–2006. The study reviews 16 academic publications, which include 466 records from experimental plots, and records from 2073 commercial plantations across the country. The average yield recorded from experiments was 7.7 odt ha −1  year −1 , compared to commercial plantations’ yields 2.6 and 4.2 odt ha −1  year −1 for the first and second rotations, respectively. The measured area of the experimental plots seems to have an effect in the overestimation of the average yields, which can be attributed to extrapolation errors. In addition, to explain the broad differences between yield estimates, we identify the following as potential factors: near-optimal management practices and choice of land age differences and rotation lengths, edge effects, measurement methods, harvesting losses, increased mortality, and increased probability of hazard. The results can help to rationalize the expectations derived from experiments and to a more realistic planning of future plantation schemes.

Description: We illustrate a detailed compositional characterization of hydrothermal liquefaction (HTL) oils derived from two biochemically distinct microalgae, Nannochloropsis gaditana and Chlorella sp. (DOE 1412), for a range of reaction temperature as observed by high-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The unique capability to unequivocally derive molecular formulae directly from FT-ICR MS-measured mass-to-charge ratio (for several thousand compounds in each oil) shows that lipids are completely reacted/converted for any reaction temperature above 200 °C and reveals the formation of nonlipid reaction products with increasing temperature. Specifically, lipid-rich oil is obtained at low reaction temperature (〈225 °C) for both microalgal strains. For positive ion mode, the major lipid components in Chlorella sp. and N. gaditana HTL oils are betaine lipids and acylglycerols, respectively. Acidic species in the HTL oils (observed by negative ion mode) are dominated by free fatty acids (FFA) regardless of reaction temperature. HTL oils obtained at higher temperatures (≥225 °C) are composed of a variety of basic nitrogen- and oxygen-containing compounds that originate from protein and carbohydrate degradation at elevated temperature. Similar structural features are observed for the abundant nitrogen heterocyclics between the two strains with slightly lower carbon number for Chlorella sp., overall.

Description: Urban biomass from green areas is a potential resource for bioenergy recovery, which is widely unused. Different types of organic material (e.g., grass, leaf litter) usually occur in mixtures due to common collecting practice. Forty samples of grass, leaf litter (genera: Acer , Quercus , Tilia ), and mixtures of both, containing one third grass or leaf litter, were investigated to evaluate the effect of the “Integrated Generation of Solid Fuel and Biogas from Biomass” (IFBB) on material and energy fluxes as well as relevant characteristics of resulting energy carriers. IFBB divides biomass into a fiber-rich press cake and a highly digestible press fluid by mashing with subsequent pressing. Ensiling of samples was successful with pH values ranging from 4.2 in grass to 4.8 in pure Tilia samples. Concentration of most minerals with exception of Ca and Mg were higher in grass than in leaf litter silage. The IFBB treatment reduced the element concentration in the press cake independently from the substrate. Linear regression models revealed high influence of the initial concentration in silage on the concentration in the press cake. The lower heating value of the press cake was nearly constant (19 MJ kg −1 DM ash free ) independent from mixture. Methane yields from press fluid digestion ranged from 172 (mean of leaf litter samples) to 325 l N  kg −1 VS (mixture of 33 % leaf litter—66 % grass). For an evaluation of the economic and ecological potential, models of the spatial and temporal occurrence of these biomasses need to be established.

Description: Physicochemical characteristics of corn stover pretreated by soaking in aqueous ammonia (SAA) and low-moisture anhydrous ammonia (LMAA) were compared and investigated. The glucan digestibility of the treated biomass reached 90 % (SAA) and 84 % (LMAA). The LMAA pretreatment enhanced the digestibility by cleaving cross-linkages between cell wall components, whereas the SAA pretreatment additionally improved the digestibility by efficiently removing a major portion of the lignin under mild reaction conditions without significant loss of carbohydrates. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC) revealed the structural and chemical transformations of lignin during the pretreatments. Both pretreatments effectively cleaved ferulate cell wall cross-linking that is associated with the recalcitrance of grass lignocellulosics toward enzymatic saccharification. Extracted lignin from SAA pretreatment was extensively depolymerized but retained “native” character, as evidenced by the retention of β-ether linkages.

Description: Potential environmental impacts of biogas electricity from agricultural residues (maize stover) with steam explosion (SE) pretreatment were compared to a typical Austrian biogas system (maize silage) using the method of life cycle assessment. Besides the biogas plant, the system includes substrate production, a combined heat-and-power (CHP) unit, digestate management, and transportation. The stover scenario (including construction and operation of the SE unit) results in lower total climate change impacts than those of the typical biogas system (239 g CO 2 -eq/kWh electricity vs. 287 g CO 2 -eq/kWh electricity; 100-year global warming potential (GWP)), and this holds also for the other impact categories (e.g., cumulative energy demand, acidification, eutrophication). While uncertainties in other areas could change the results, based on the uncertainty information considered, the overall results for the two scenarios were significantly different. Methane slip emissions from the CHP exhaust account for the largest GWP share in both scenarios. Other large GWP contributions are from substrate production and grid electricity for plant operations. The findings were robust against worst-case assumptions about the energy requirements of the SE pretreatment.

Description: To identify switchgrass homologs of rice genes, known/predicted to control biomass and stress response-related traits, we screened 96,000 clones from two switchgrass bacterial artificial chromosome (BAC) libraries. Full-length sequencing of 311 BAC clones revealed sequence for ∼3.2 % (51.7 Mb) of the switchgrass genome, coding for 3948 genes. A comparison with Arabidopsis and five grass genomes revealed that switchgrass genes share the highest number of homologs with rice (95.5 %) followed by foxtail millet (91.7 %) and Sorghum (91.5 %). One hundred eighteen of the annotated genes are unique to switchgrass. Gene annotation and ontology analysis revealed 695 genes belonging to gene families targeted in the screening. These include 350 kinase, 203 glycosyltransferase (GT), 109 glycoside hydrolase (GH), and 33 ethylene responsive transcription factor (ERF) family genes. Rice homologs of 65 genes, identified here, have demonstrated roles in bioenergy-relevant traits. These include 14 GT2 family genes involved in the synthesis of cellulose and hemicelluloses. Comparative expression analysis in six switchgrass organs revealed a conserved expression pattern for three cellulose synthase ( CesA1 , CesA2 , and CesA9 ) and five cellulose-synthase-like genes ( CslA2 , CslA11 , CslC1 , CslD4 , and CslE6 ). CslF genes that encode mixed linkage glucans are expressed in wider range of tissues in switchgrass compared with rice.

Description: Kenaf ( Hibiscus cannabinus L.) has potential as an annual herbaceous biomass feedstock. It is not typically grown in the American Midwest; however, kenaf may be attractive as an alternative crop for Iowa and the Corn Belt. In this study, seven kenaf varieties were grown in Iowa and evaluated for their productivity. More specifically, our research questions were the following: (1) how do kenaf varieties perform in Iowa for yield? (2) How does fiber morphology and quality differ among varieties and among core and bast fiber? And (3) What potential does kenaf (bast and core) have for producing fuel using fast pyrolysis? Tainung 2, one of the varieties, reached the best yield in Central Iowa over multiple years. Bast kenaf contained 8 % more cellulose and 23 % less hemicellulose than the core but it varied among varieties. Also, regardless of variety, core was composed of 40 % more lignin than bast. Core was found to have higher potential for fast pyrolysis than the bast but its potential was variety-dependent. Overall, kenaf could be grown to diversify Iowa agriculture and provide alternative feedstock to the biofuel industry.

Description: Levulinic acid (LA) is a versatile platform chemical that can be derived from biomass as an alternative to fossil fuel resources. Herein, the optimization of LA production from glucose and oil palm fronds (OPF) catalyzed by an acidic ionic liquid; 1-sulfonic acid-3-methyl imidazolium tetrachloroferrate ([SMIM][FeCl 4 ]) have been investigated. Response surface methodology based on Box-Behnken design was employed to optimize the LA yield and to examine the effect and interaction of reaction parameters on the LA production. The reaction parameters include reaction temperature, reaction time, feedstock loading, and catalyst loading. From the optimization study, the predicted mathematical models for LA production from glucose and OPF covered more than 90 % of the variability in the experimental data. At optimum conditions, 69.2 % of LA yield was obtained from glucose, while 24.8 % of LA yield was attained from OPF and registered 77.3 % of process efficiency. The recycled [SMIM][FeCl 4 ] gave sufficient performance for five successive cycles. Furthermore, the optimum LA produced from glucose and OPF can be directly converted to ethyl levulinate through esterification over the [SMIM][FeCl 4 ] catalyst. This study highlights the potential of [SMIM][FeCl 4 ] for biorefinery processing of renewable feedstocks at mild process conditions.

Description: Since they have a high concentrations of fermentable sugars, sweet pearl millet and sweet sorghum are two interesting crops for bioethanol production. However, if the juice is not extracted from the biomass immediately after harvest, the biomass has to be transported and stored for further juice extraction. This delay could affect the amount of juice extracted and its sugar concentration. This paper presents the results of 3 years of experiments where different storage modes (chopped and whole stalks) and various storage time (0 to 14 days) were applied on two different crop species (sweet pearl millet and sweet sorghum). Storing sweet pearl millet as whole stalks for 2 weeks resulted in a water-soluble carbohydrate (WSC) concentration decrease of 52 %, while no significant decrease of the WSC concentration was observed for sweet sorghum. Whole stalks storage is much more efficient than storing the biomass chopped to avoid a rapid sugar loss. However, more juice can be extracted from stored chopped biomass than from stored whole stalks biomass. If the juice cannot be extracted quickly after the harvest, the biomass can be stored as whole stalks to avoid rapid sugar deterioration, especially for sweet sorghum.

Description: High-strength wastewaters after being digested for biogas production in anaerobic digesters still contain substantial nutrients and organics. The anaerobic digestates from four major industries in Thailand were tested with batch cultivation of Chlorella sp. for oil production potentials. Pig farm digestate was found most suitable as the growth medium generating 0.95 g/L medium (dry biomass), which was 1.16–3.06 times of other digestates tested. Considerable removals of nitrogen and phosphorus achieved were an added benefit to the goal of ultimate treatment of these wastewaters. Light intensity had strong influence on growth and heterotrophic metabolism up to 78 μmol/m 2 /s, while the dilution of digestate above 2.4× diminished growth potential and lipid production. A quadratic regression model was constructed to describe interaction of light intensity, dilution factor, and time of cultivation to lipid production with a satisfactory precision. Light intensity could influence fatty acid composition, although palmitic acid was found predominant at 47.1 %. The algae oil generated could potentially increase the total energy output from anaerobic digesters of a typical pig farm by 22 %.

Description: The carbon (C) dynamics of a bioenergy system are key to correctly defining its viability as a sustainable alternative to conventional fossil fuel energy sources. Recent studies have quantified the greenhouse gas mitigation potential of these bioenergy crops, often concluding that C sequestration in soils plays a primary role in offsetting emissions through energy generation. Miscanthus is a particularly promising bioenergy crop and research has shown that soil C stocks can increase by more than 2 t C ha −1  yr −1 . In this study, we use a stable isotope ( 13 C) technique to trace the inputs and outputs from soils below a commercial Miscanthus plantation in Lincolnshire, UK, over the first 7 years of growth after conversion from a conventional arable crop. Results suggest that an unchanging total topsoil (0–30 cm) C stock is caused by Miscanthus additions displacing older soil organic matter. Further, using a comparison between bare soil plots (no new Miscanthus inputs) and undisturbed Miscanthus controls, soil respiration was seen to be unaffected through priming by fresh inputs or rhizosphere. The temperature sensitivity of old soil C was also seen to be very similar with and without the presence of live root biomass. Total soil respiration from control plots was dominated by Miscanthus -derived emissions with autotrophic respiration alone accounting for ∼50 % of CO 2 . Although total soil C stocks did not change significantly over time, the Miscanthus -derived soil C accumulated at a rate of 860 kg C ha −1  yr −1 over the top 30 cm. Ultimately, the results from this study indicate that soil C stocks below Miscanthus plantations do not necessarily increase during the first 7 years.

Description: Modeling the life cycle of fuel pathways for cellulosic ethanol (CE) can help identify logistical barriers and anticipated impacts for the emerging commercial CE industry. Such models contain high amounts of variability, primarily due to the varying nature of agricultural production but also because of limitations in the availability of data at the local scale, resulting in the typical practice of using average values. In this study, 12 spatially explicit, cradle-to-refinery gate CE pathways were developed that vary by feedstock (corn stover, switchgrass, and Miscanthus), nitrogen application rate (higher, lower), pretreatment method (ammonia fiber expansion [AFEX], dilute acid), and co-product treatment method (mass allocation, sub-division), in which feedstock production was modeled at the watershed scale over a nine-county area in Southwestern Michigan. When comparing feedstocks, the model showed that corn stover yielded higher global warming potential (GWP), acidification potential (AP), and eutrophication potential (EP) than the perennial feedstocks of switchgrass and Miscanthus, on an average per area basis. Full life cycle results per MJ of produced ethanol demonstrated more mixed results, with corn stover-derived CE scenarios that use sub-division as a co-product treatment method yielding similarly favorable outcomes as switchgrass- and Miscanthus-derived CE scenarios. Variability was found to be greater between feedstocks than watersheds. Additionally, scenarios using dilute acid pretreatment had more favorable results than those using AFEX pretreatment.

Description: European agricultural policy increasingly focuses on environmental friendly cropping systems. Intercropping of maize ( Zea mays L.) and common beans ( Phaseolus vulgaris L.) has been suggested as an alternative cropping system with environmental benefits. The aim of this study was to assess methane yield potential of mixed silages. Based on material from two field experiments at three sites in Germany, mixed silages were produced with proportions of individual components varying from 0 to 100 % of fresh matter in increments of 12.5 %. Chemical parameters (neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (XP), starch, sugar, and crude fat) were determined, and batch tests were performed to measure methane yield potential from silages. With increasing bean proportion, concentrations of XP increased while NDF, methane yield, and methane content decreased. While methane yield showed a negative relationship with XP content ( R 2  = 0.56***), a positive relation was found with NDF ( R 2  = 0.55***). The reduction of methane yield of circa 1 L of methane per each additional bean percentage in the silages could not be explained by the chemical parameters of the silages. It is hypothesized that other chemical compounds, such as lectins, which were not determined in the present study, may have influenced methane production.

Description: The sustainable development of miscanthus as a bioenergy feedstock requires optimizing its fertilizer inputs and, therefore, determining its nitrogen (N) requirements. The ‘critical nitrogen dilution curve’ is a powerful tool to characterize such N requirements; it relates the N concentration ([N]) in aboveground organs to their biomass, defining two domains depending on whether the N factor limits biomass growth or not. We aimed to develop such a tool in miscanthus. Using a rhizome N depletion strategy with green cutting pre-treatment over several years before the start of the experiment, we grew, in 2014, two cultivated species, Miscanthus × giganteus ( M × g ) and Miscanthus sinensis ( Msin ), at four fertilizer levels (0, 80, 160 and 240 kg N ha −1 ). We found a strong nitrogen fertilization effect. The shoot [N] decreased as the aboveground biomass increased in both species and in all of the treatments. [N] was strongly correlated with leaf/stem biomass ratio. The N treatments enabled the identification of the observed critical points, i.e. points with the maximum biomass ( W ) and the lowest [N], on each measurement date. These points could be fitted to the following critical dilution curve that was common between M × g and Msin : N concentration ( Nc ) (critical [N], g N kg −1 ) = 27.0  W −0.48 when W  〉 1 t ha −1 and Nc  = 27.0 when W  ≤ 1. This curve was validated by literature data, separated into N-limited or not-limited conditions. The similarity of the curves between the two species was due to compensation between leaf/stem biomass ratio and [N] in the stems. This curve is helpful to diagnose the crop N status and define the optimal fertilizer requirements of miscanthus crops.

Description: Jatropha curcas , a promising bioenergy crop is becoming vulnerable to various biotic stresses due to large-scale cultivation of selected genotypes, thereby affecting its yield potential. Virus causing mosaic disease is prevalent in Jatropha plantations and causing significant reduction in seed yield and quality. To better understand the molecular mechanisms associated with virus infection response, we performed RNA-seq-based comprehensive transcriptome sequencing of symptomatic virus-infected (JV) and healthy (JH) leaf tissues of J. curcas . Through reference genome-based mapping approach, 55,755 genes expressed in both samples were identified. Differential expression analysis identified genes linked to various pathways, upregulated and downregulated during mosaic virus infection. Upon KEGG-based functional annotation, it was observed that various metabolism-associated processes along with oxidative phosphorylation, endocytosis, terpenoid biosynthesis, and hormone signal transduction were upregulated whereas photosynthesis, anthocyanin biosynthesis, plant-pathogen interaction, and calcium signaling were downregulated in response to virus infection. Significantly, genes associated with hormone signal transduction were upregulated as physiological symptoms induced upon mosaic virus infection is due to the interplay of various phytohormones regulating general growth and development of plant. Also, many genes regulating photosynthesis which were downregulated during virus infection showed repressed rate of photosynthesis and also reduction in seed yield and oil content upon mosaic virus infection in J. curcas . RT-qPCR-based experimental validation approach was supplemented to confirm the computational identification. The study provides a repertoire of molecular components which have been affected in response to virus infection, and their precise role can be further functionally validated.

Description: Eight willow ( Salix ) clones (Inger, Klara, Linnea, Resolution, Stina, Terra Nova, Tora, Tordis) were planted on two soil types in Denmark. The biomass quality was evaluated after 3 years of growth by measuring differences in concentrations of 14 elements associated with ash behavior during combustion, and total ash content. Three-year-old shoots of Tordis and Tora performed in general the best with relatively lower mean concentrations of K, Ca, Na, S, and total ash content than other clones across the two experimental sites. Terra Nova was the least suited for combustion as it contained up to 22, 27, 35, and 23 % higher concentrations of K, S, Ca, and total ash than the other clones. In addition to clone and site, appropriate management could further improve the fuel quality of willow biomass. When shoots of Inger were harvested annually (1-year shoots) high concentrations of K and Cl were found in all three consecutive harvests, but concentrations decreased significantly when rotation length was extended beyond 1 year of growth. Significant decreases of Mg, Na, P, S, and Zn were also registered from 2- to 3-year-old shoots. No difference in quality of biomass was found between two plant densities (8000 and 12,000 trees ha −1 ) of the clones Inger and Tora after the first 3-year rotation when grown at the site with a coarse sandy soil. The study indicates considerable diversity in concentration of elements within commercially available willow cultivars and suggests breeders and growers to select clones not only according to biomass yield potential but also according to biomass quality.

Description: Integration of algae production with livestock waste management has the potential to recover energy and nutrients from animal manure, while reducing discharges of organic matter, pathogens, and nutrients to the environment. In this study, microalgae Chlorella sp. were grown on centrate from anaerobically digested swine manure. The algae were harvested for mesophilic anaerobic digestion (AD) with swine manure for bioenergy production. Low biogas yields were observed in batch AD studies with algae alone, or when algae were co-digested with swine manure at ≥43 % algae (based on volatile solids [VS]). However, co-digestion of 6–16 % algae with swine manure produced similar biogas yields as digestion of swine manure alone. An average methane yield of 190 mL/g VS fed was achieved in long-term semi-continuous co-digestion studies with 10 ± 3 % algae with swine manure. Data from the experimental studies were used in an energy analysis assuming the process was scaled up to a concentrated animal feeding operation (CAFO) with 7000 pigs with integrated algae-based treatment of centrate and co-digestion of manure and the harvested algae. The average net energy production for the system was estimated at 1027 kWh per day. A mass balance indicated that 58 % of nitrogen (N) and 98 % of phosphorus (P) in the system were removed in the biosolids. A major advantage of the proposed process is the reduction in nutrient discharges compared with AD of swine waste without algae production.

Description: Lignocellulosic ethanol is a promising alternative to fossil-derived fuels because lignocellulosic biomass is abundant, cheap and its use is environmentally friendly. However, the high costs of feedstock supply and the expensive processing requirements of lignocellulosic biomass hinder the development of the lignocellulosic biorefinery. Lignocellulosic ethanol production so far, has been based mainly on single feedstocks while the use of mixed feedstocks has been poorly explored. Previous studies from alternative applications of mixed lignocellulosic biomass (MLB) have shown that their use can bring about significant cost savings when compared to single feedstocks. Although laboratory-scale evaluations have demonstrated that mixed feedstocks give comparable or even higher ethanol yields compared to single feedstocks, more empirical studies are needed to establish the possibility of achieving significant cost savings in terms of pre-biorefinery logistics. In this review, some potential benefits of the use of MLB for ethanol production are highlighted. Some anticipated limitations of this approach have been identified and ways to surmount them have been suggested. The outlook for ethanol production from MLB is promising provided that revolutionary measures are taken to ensure the sustainability of the industry.

Description: Appropriate canopy management, including planting density and pruning, and application of fertilizer may increase flowering success and seed and oil yields of Jatropha curcas L. Two field experiments were performed from 2009 to 2011 in Balaka, Malawi, to assess the effect of planting density and pruning regime and single fertilizer application (N, P, and K) on male and female flower number and seed and oil yields of J. curcas . Planting density influenced flower sex ratio and female flower number. Branch pruning treatments did not influence the flower sex ratio but reduced seed and final oil yield by 55 % in the following year. It is claimed that J. curcas can be grown on soils with low nutrient content, but this study revealed that yield was low for non-fertilized trees. We observed higher seed and oil yields at higher N application rates (up to 203 ± 42 % seed and 204 ± 45 % oil yield increase) compared with the non-fertilized control. The study suggests thatcurrently used heavy pruning practice is not recommended for J. curcas cultivation, although it needs further longer term investigation. Applying nitrogen fertilizer is effective in increasing yield.

Description: Ethanol produced from lignocellulosic feedstock is a promising alternative to fossil fuels and corn-sourced ethanol. However, it creates unique challenges in terms of requirements for breakdown to fermentable sugars, including the need for pretreatment and enzymatic hydrolysis of structural carbohydrates. Hydrolases from microorganisms are currently utilized for biomass hydrolysis in the production of lignocellulosic ethanol; however, expressing these hydrolases in lignocellulosic feedstock is a favorable alternative, due to the large availability of biomass and the potential for the feedstock to play a dual role as both biomass substrate and enzyme provider. This review summarizes recent achievements in hydrolytic enzyme expression in a variety of model plants and potential feedstocks, including strategies to improve enzyme yield and to prevent deleterious effects on plants hosts. We propose possible scenarios for utilizing enzyme-expressing transgenic feedstock and illustrate the potential benefits of using these crops for ethanol production. Furthermore, challenges are highlighted and potential solutions proposed to move the field forward to cost-comparable lignocellulosic ethanol.

Description: Owing to its sugar-rich stalks and high biomass, sweet sorghum [ Sorghum bicolor (L.) Moench] has potential as a source of biofuel feedstock for juice and lignocellulosic-based bioethanol production. However, stalk rot-mediated lodging is an important concern. The potential impacts of disease on sweet sorghum biofuel traits are currently unknown. The objectives of this study were to test the effects of Fusarium stalk rot and charcoal rot on sweet sorghum biofuel traits and to assess the combining ability of the parental genotypes for resistance to the two diseases. Nineteen genotypes including 7 parents and 12 hybrids were tested in the field in 2014 (Ashland, Kansas) and 2015 (Manhattan, Kansas) against Fusarium thapsinum (FT) and Macrophomina phaseolina (MP). Fourteen days after flowering, plants were inoculated with FT and MP. Plants were harvested at 35 days after inoculation and measured for disease severity using stalk lesion length. Grain weight, juice weight, Brix (°Bx), and dried bagasse weight were also determined. Total soluble sugars per plant (TSSP) were determined using juice weight and °Bx. On average, FT and MP resulted in reduced grain weight and dried bagasse weight by 17.4 and 17.6 %, respectively, across genotypes. Depending on the genotype, pathogens reduced juice weight, °Bx, and TSSP in the ranges of 11.3 to 25.9, 0.2 to 16.7, and 21.2 to 33.3 %, respectively. Parental line general and specific combining abilities were found to be statistically insignificant. This study revealed the adverse effects of stalk rot diseases on harvestable biofuel traits and the need to breed sweet sorghum for stalk rot resistance.

Description: The architecture, composition, and chemical properties of wood cell walls have a direct influence on the process that occurs prior to fermentation in second-generation biofuel production. The understanding of the construction patterns of cell wall types is the key to the new era of second-generation biofuels. Eucalyptus species are great candidates for this purpose since these species are among the fastest growing hardwood trees in the world and they have been improved for biomass production. We applied the glycome profiling and other combined techniques to study xylem cell walls of three economically important species ( Eucalyptus globulus , Eucalyptus grandis , and Eucalyptus urophylla ). Glycome profiling analyses revealed that species differ in the same key aspects of cell wall polymer linkages, with E. globulus and E. urophylla presenting contrasting phenotypes, and E. grandis with intermediate characteristics . E. urophylla is known for high recalcitrance, that is probably determined by the strong associations between lignin and cell wall polymers, and also lignin content. On the other hand, E. globulus cell wall polymers are loosely linked, so its cell wall can be easily deconstructed. We have shown in this work that the composition of cell walls differs in quantity and quality among the Eucalyptus species and such variations in composition influence the process of lignocellulosic feedstock assessment. However, the greatest influence relies on the amount and type of associations between cell wall polymers. A high yield of cellulose, from any biomass source, directly depends on the cell wall architecture.

Description: Switchgrass ( Panicum virgatum L.) is currently undergoing intensive breeding efforts to improve biomass yield. Consideration must be made regarding the relative importance of spaced plantings to sward plots for evaluation and selection for increased biomass yield. It has previously been suggested that selection schemes using secondary plant morphological traits as selection criteria within spaced plantings may be an efficient method of making genetic gain. The objective of this study was to empirically test the effects of direct selection for plant height, tiller count, flowering date, and visual selection for biomass yield within spaced plantings on biomass yield and morphology traits within sward plots. Divergently selected populations for each trait were developed from the WS4U upland tetraploid germplasm and evaluated for biomass yield at five locations in Wisconsin during two growing seasons. Significant variation was observed between maternal parents of the selected populations for both selected and nonselected traits. Despite substantial differences between parent plant populations for plant morphology, significant differences were not observed for sward-plot biomass yield or sward-plot morphology relative to the base population. Late flowering selections yielded 2.0 Mg/ha greater biomass than early flowering selections (29 % increase). Plant height within sward plots was observed to have a strong positive correlation with biomass yield. Tiller count was observed to have a weak correlation with biomass yield. Based on the observed results, it is recommended that greater emphasis be placed on evaluation of biomass yield using sward plots.

Description: Lipids created via microbial biosynthesis are a potential raw material to replace plant-based oil for biodiesel production. Oleaginous microbial species currently available are capable of accumulating high amount of lipids in their cell biomass, but rarely can directly utilize lignocellulosic biomass as substrates. Thus this research focused on the screening and selection of new fungal strains that generate both lipids and hydrolytic enzymes. To search for oleaginous fungal strains in the soybean plant, endophytic fungi and fungi close to the plant roots were studied as a microbial source. Among 33 endophytic fungal isolates screened from the soybean plant, 13 have high lipid content (〉20 % dry biomass weight); among 38 fungal isolates screened from the soil surrounding the soybean roots, 14 have high lipid content. Also, five fungal isolates with both high lipid content and promising biomass production were selected for further studies on their cell growth, oil accumulation, lipid content and profile, utilization of various carbon sources, and cellulase production. The results indicate that most strains could utilize different types of carbon sources and some strains accumulated 〉40 % of the lipids based on the dry cell biomass weight. Among these promising strains, some Fusarium strains specifically showed considerable production of cellulase, which offers great potential for biodiesel production by directly utilizing inexpensive lignocellulosic material as feedstock.

Description: This study applied dilute acid (DA) and sulfite pretreatment to overcome the recalcitrance of lignocelluloses (SPORL) to deconstruct earlywood and latewood cell walls of Douglas fir for fermentable sugars production through subsequent enzymatic hydrolysis. DA pretreatment removed almost all the hemicelluloses, while SPORL at initial pH = 4.5 (SP-B) removed significant amount of lignin between 20 and 25 %. But both are not sufficient for effective enzymatic saccharification. SPORL at low initial pH = 2 (SP-AB) combines the advantage of both DA and SPORL-B to achieve approximately 90 % hemicellulose removal and delignification of 10–20 %. As a result, SP-AB effectively removed recalcitrance and thereby significantly improved enzymatic saccharification compared with DA and SP-B. Results also showed that earlywood with significantly lower density produced less saccharification after DA pretreatment, suggesting that wood density does not contribute to recalcitrance. The thick cell wall of latewood did not limit chemical penetration in pretreatments. The high lignin content of earlywood limited the effectiveness of DA pretreatment for enzymatic saccharification, while hemicellulose limits the effectiveness of high pH pretreatment of SP-B. The higher hemicellulose content in the earlywood and latewood of heartwood reduced saccharification relative to the corresponding earlywood and latewood in the sapwood using DA and SP-AB.

Description: Willow, a leading bioenergy feedstock, may be planted for bioremediation and has been used, more recently, as the biomass feedstock in the manufacture of biochar for agricultural applications. Here, we present a detailed study of the physical and chemical factors affecting willow char properties, where the feedstock is a by-product of bioremediation, potentially transferring pollutants such as heavy metals to the wood feed. Biochar samples were produced via pyrolysis of short-rotation coppice willow, grown on contaminated land, using several treatment times at heat treatment temperatures (HTTs) in the range 350–650 °C, under a constant flow of argon, set at either 100 or 500 mL min −1 . The samples were analysed for yield, elemental analysis and structural characteristics, including surface area and pore size distribution, surface functionality and metal content. All chars obtained have high fixed carbon contents but vary in surface characteristics with a marked increase in basic character with increasing HTT, ascribed to the removal of surface oxygen moieties. Results indicate a minimum pyrolysis temperature of 450 °C is required to produce a defined mesoporous structure, as required to facilitate oxygen transport, HTT ≥ 550 °C produces total surface area of 〉170 m 2  g −1 and, more importantly, an appreciable external surface area suitable for microbial colonisation. The data show that selection and optimisation of char properties is possible; however, the interplay of factors may mean some compromise is required.

Description: Increasing specific activity of cellulase on solid cellulosic materials would be among the top priorities for second-generation biorefineries. However, the complicated relationship among the heterogeneity of solid cellulosic materials and different action mode cellulase components results in great challenges in cellulase engineering. We applied directed evolution to a Clostridium phytofermentans ISDg glycoside hydrolase family 9 processive endoglucanase (CpCel9) for enhanced hydrolytic performance by using Bacillus subtilis as a host for cloning and expression. Several CpCel9 mutants with both increased expression level and enhanced specific activity on the solid cellulosic material were obtained. The most active mutant, which also exhibits an increased expression level, had more than threefold specific activity than that of wild type on regenerated amorphous cellulose. Most mutation sites were located in the family 3 cellulose-binding module near to its catalytic module, which might guide the entrance of glucan into the catalytic module. This study suggested that directed evolution by combining B. subtilis secretory protein expression host and solid cellulosic substrates would be a powerful tool to evolve more active cellulase mutants for cost-effective biosaccharification process.

Description: This study comparatively evaluates the modelling efficiency of the Response Surface Methodology (RSM) and the Artificial Neural Network (ANN). Twenty-nine biohydrogen fermentation batches were carried out to generate the experimental data. The input parameters consisted of a concentration of molasses (50–150 g/l), pH (4–8), temperature (35–40 °C) and inoculum concentration (10–50 %). The obtained data were used to develop the RSM and ANN models. The ANN model was a committee of networks with a topology of 4-(6-10)-1 structured on multilayer perceptrons. RSM and ANN models gave R 2 values of 0.75 and 0.91, respectively, with predicted optimum conditions of 150 g/l, 8 and 35 °C for molasses, pH and temperature, respectively, with differences in inoculum concentrations (10.11 and 15 %) for RSM and ANN, respectively. Upon validation, 15.12 and 119.08 % prediction errors on hydrogen volume were found for ANN and RSM, respectively. These findings suggest that ANN has greater accuracy in modelling the relationships between the considered process inputs for fermentative biohydrogen production and thus, is more reliable to navigate the optimization space.

Description: Short rotation coppice (SRC) willow is an emerging cropping system in focus for production of biomass for energy. To increase production, the willow is commonly fertilized, but studies have shown differing effects of fertilization on biomass production, ranging from almost no response to considerable positive effects. Focus has also been on replacing mineral fertilizer with organic waste products, such as manure and sludge. However, the effect on biomass production and environmental impact of various dosage and types of fertilizer is not well described. Therefore we studied the environmental impacts of different doses of mineral fertilizer, manure and sewage sludge in a commercially grown SRC willow stand. We examined macro nutrient and heavy metal leaching rates and calculated element balances to evaluate the environmental impact. Growth responses were reported in a former paper (Sevel et al. “Fertilization of SRC Willow, I: Biomass Production Response” Bioenergy Research, 2013). Nitrogen leaching was generally low, between 1 and 7 kg N ha −1  year −1 when doses of up to 120 kg N ha −1  year −1 were applied. Higher doses of 240 and 360 kg N ha −1 as single applications caused leaching of 66 and 99 kg N ha −1  year −1 , respectively, indicating N saturation of the system. Previous intensive farming including high doses of fertilizer may be responsible for a high soil N status and the high N leaching rates. However, moderate fertilization input could not compensate P and K exports with the biomass harvest. No elevated leaching of heavy metals was observed for any fertilization treatments and more cadmium than applied with the fertilizer was removed with the biomass from the system.

Description: Short rotation coppice (SRC) willow is often regarded as one of the most promising crops to increase biomass production and thereby meet the growing demand for renewable energy. This study is based on the hypotheses that biomass production of SRC willow responds positively to increasing doses of nitrogen, and that similar biomass production response can be achieved by use of mineral fertilizer, sewage sludge and animal manure. A 2-year experiment was established with the clone Tordis grown on a sandy soil in northern Jutland, Denmark. The experiment included mineral fertilizer, sludge and manure, and treatments of different doses up to 360 kg nitrogen ha −1 . The fertilization led to a modest but significant increase in biomass production. The largest production of 11.9 oven dried tons/ha/year was obtained for the application of 60 kg nitrogen ha −1 annually. Higher doses did not lead to increased biomass production; in fact, production seemed to decline with increasing fertilization application (not significant). We found no difference in production between different types of fertilizers. The limited response of the fertilization may be caused by a high fertility of the soil due to former agricultural fertilization. The number of sagging shoots increased significantly with increasing nitrogen dose.

Description: The technique of near and short wave near-infrared spectroscopy was assessed with respect to analysis of dry matter and lipid content of microalgae with potential for biodiesel production. Microalgal culture samples were filtered through GF/C filter papers and spectral measurements of wet and oven dried (60 °C overnight) filter papers over the ranges of 300–1,100 nm and 1,100–2,500 nm were recorded. Partial least square models on culture biomass and lipid content for combined species data were poor in terms of RMSECV, R CV and the ratio of RMSECV to SD. A single species model for C. vulgaris based on 1,100–2,500 nm spectra of dry filtrate supported a model with RMSECV, R CV and SDR values of 0.32 g L −1 , 0.955 and 3.38 for biomass and 0.089 g L −1 , 0.874 and 2.06 with lipid, respectively. However, the dry filtrate models on biomass and lipid content performed poorly in the prediction of samples drawn from an independent series of C. vulgaris cultured under N-, P- and Fe-limited growth trial. Thus, while the near-infrared spectroscopy technique has potential for assessment of dry matter and lipid content of microalgal cultures using a dried filtrate sample, further work is required to examine the limits to model robustness.

Description: Biofuels can play an important role in decreasing the use of fossil fuels, in particular in the transport sector, which absorbs about 30 % of the EU energy requirements. This review illustrates the motivations behind biofuel development, the government incentives and regulations and the current approaches on sustainable biomass conversion in Europe, and provides an overview on the major steps involved in thermochemical processes and on the issues challenging their deployment at large scale, with particular emphasis on the pyrolysis of biomass and bio-oil upgrading using conventional oil refinery settings. Distribution of sustainable biofuels in Europe and future prospects towards achieving success of transport biofuels were also addressed. The literature suggests that importing biofuels and increasing the cost of CO 2 to at least €60/t CO 2 will be necessary to meet the renewable obligation targets in the EU. Algae represent the future feedstock for biofuels but currently are limited by their high production costs and high N content. Pyrolysis is cost competitive compared to other technologies such as fermentation and gasification, but the quality of bio-oils requires upgrading mainly to lower their oxygen content and enhance their thermal stability. The recent advances in bio-oil upgrading using catalytic cracking and hydro-treating are very promising for the future deployment of advanced biofuels in the coming decades. However, significant investments in applied research and demonstration are still required to meet the 2020/2030 biofuel targets.

Description: Anaerobic digestion (AD) is a biotechnology that is able to produce an energy vector from waste organic materials. Its inclusion in the food industries, especially if farming activities are present, represents an interesting perspective. This work reviews the main aspects of the inclusion of AD in milk and dairy production. It includes an analysis of the sector characteristics in terms of diffusion, a discussion of waste production and disposal concerning milk and dairy production, a description of the biological and technological aspects of AD, a discussion regarding the application of AD for milk by-products, a description of environmental and legislative aspects, and the suggestion of an integrated model that includes the anaerobic co-digestion of whey and cattle slurry in the milk and dairy production industries. Both environmental and economic impacts of such integration promise to pay for the preliminary investment in AD plant installation and the development of additional expertise.

Description: Napiergrass ( Pennisetum purpureum Schum.) is a high-yielding perennial biomass crop that is well adapted to the Southeast USA where poultry litter is readily available. This research was conducted to compare biomass production and nutrient utilization of napiergrass fertilized with either poultry litter or inorganic fertilizer. Each spring, approximately 100 kg ha −1 of N, 40 kg ha −1 P, and 90 kg ha −1  K were applied as poultry litter or equivalent inorganic fertilizer. Biomass was harvested each winter after senescence. For the first 2 years, dry matter yield did not differ among treatments, but in the third and fourth years, yields declined in all treatments and were lowest in the unfertilized treatment. Biomass N concentration and N removal were greatest in the inorganic treatment. In general, N removal exceeded the amount applied, suggesting that higher application rates may be necessary to maintain yields. Biomass P concentration and total P uptake were greatest in the litter fertilized treatment, demonstrating that napiergrass can remove some of the excess P from applied litter. Soil cores were taken periodically to assess changes in soil properties. After 2 years of production, soil pH in the surface layer (0–15 cm) was lower in the inorganic treatment than in the other treatments. After 4 years, total soil C had increased by an average of 3,180 kg ha −1 though fertilizer treatments did not differ. Yield declined in all treatments after 4 years and N supplementation is recommended for production in upland fields.

Description: Switchgrass ( Panicum virgatum L.) is a native perennial warm season (C 4 ) grass that has been identified as a promising species for bioenergy research and production. Consequently, biomass yield and feedstock quality improvements are high priorities for switchgrass research. The objective of this study was to develop a switchgrass genetic linkage map using a full-sib pseudo-testcross mapping population derived from a cross between two heterozygous genotypes selected from the lowland cultivar ‘Alamo’ (AP13) and the upland cultivar ‘Summer’ (VS16). The female parent (AP13) map consists of 515 loci in 18 linkage groups (LGs) and spans 1,733 cM. The male parent (VS16) map arranges 363 loci in 17 LGs and spans 1,508 cM. No obvious cause for the lack of one LG in VS16 could be identified. Comparative analyses between the AP13 and VS16 maps showed that the two major ecotypic classes of switchgrass have highly colinear maps with similar recombination rates, suggesting that chromosomal exchange between the two ecotypes should be able to occur freely. The AP13 and VS16 maps are also highly similar with respect to marker orders and recombination levels to previously published switchgrass maps. The genetic maps will be used to identify quantitative trait loci associated with biomass and quality traits. The AP13 genotype was used for the whole genome-sequencing project and the map will thus also provide a tool for the anchoring of the switchgrass genome assembly.

Description: To date, cellulosic ethanol production has not been commercialized in the United States. However, government mandates aimed at increasing second-generation biofuel production could spur exploratory development in the cellulosic ethanol industry. We conducted an in-depth analysis of the fuelshed surrounding a starch-based ethanol plant near York, Nebraska that has the potential for cellulosic ethanol production. To assess the feasibility of supplying adequate biomass for year-round cellulosic ethanol production from residual maize ( Zea mays ) stover and bioenergy switchgrass ( Panicum virgatum ) within a 40-km road network service area of the existing ethanol plant, we identified ∼14,000 ha of marginally productive cropland within the service area suitable for conversion from annual rowcrops to switchgrass and ∼132,000 ha of maize-enrolled cropland from which maize stover could be collected. Annual maize stover and switchgrass biomass supplies within the 40-km service area could range between 429,000 and 752,000 metric tons (mT). Approximately 140–250 million liters (l) of cellulosic ethanol could be produced, rivaling the current 208 million l annual starch-based ethanol production capacity of the plant. We conclude that sufficient quantities of biomass could be produced from maize stover and switchgrass near the plant to support year-round cellulosic ethanol production at current feedstock yields, sustainable removal rates and bioconversion efficiencies. Modifying existing starch-based ethanol plants in intensive agricultural fuelsheds could increase ethanol output, return marginally productive cropland to perennial vegetation, and remove maize stover from productive cropland to meet feedstock demand.

Description: Expected future cellulosic ethanol production increases the demand for biomass in the US Corn Belt. With low nutritious value, low nitrogen content, and compact biomass, maize cobs can provide a significant amount of cellulosic materials. The value of maize cobs depends on cob architecture, chemical composition, and their relation to grain yield as primary trait. Eight traits including cob volume, fractional diameters, length, weight, tissue density, and grain yield have been analyzed in this quantitative trait locus (QTL) mapping experiment to evaluate their inheritance and inter-relations. One hundred eighty-four recombinant inbred lines of the intermated B73 × Mo17 (IBM) Syn 4 population were evaluated from an experiment carried out at three locations and analyzed using genotypic information of 1,339 public SNP markers. QTL detection was performed using (1) comparison-wise thresholds with reselection of cofactors ( α  = 0.001) and (2) empirical logarithm of odds score thresholds ( P  = 0.05). Several QTL with small genetic effects ( R 2  = 2.9–13.4 %) were found, suggesting a complex quantitative inheritance of all traits. Increased cob tissue density was found to add value to the residual without a commensurate negative impact on grain yield and therefore enables for simultaneous selection for cob biomass and grain yield.

Description: We previously reported on a new yeast strain of Clavispora sp. NRRL Y-50464 that is capable of utilizing cellobiose as sole source of carbon and energy by producing sufficient native β-glucosidase enzyme activity without further enzyme supplementation for cellulosic ethanol production using simultaneous saccharification and fermentation. Eliminating the addition of external β-glucosidase reduces the cost of cellulosic ethanol production. In this study, we present results on the isolation and identification of a β-glucosidase protein from strain Y-50464. Using Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and blast search of the NCBInr database (National Center for Biotechnology Information nonredundant), the protein from Y-50464 was identified as a β-glucosidase (BGL1) with a molecular weight of 93.3 kDa. The BGL1 protein was purified through multiple chromatographic steps to a 26-fold purity ( K m  = 0.355 mM [pNPG]; K i  = 15.2 mM [glucose]), which has a specific activity of 18.4 U/mg of protein with an optimal performance temperature at 45 °C and pH of 6.0. This protein appears to be intracellular although other forms of the enzyme may exist. The fast growth rate of Y-50464 and its capability to produce sufficient β-glucosidase activity for ethanol conversion from cellobiose provide a promising means for low-cost cellulosic ethanol production through a consolidated bioprocessing development.

Description: Development of viable bioenergy economies will require large increases in biomass feedstock production. Improved methods are needed to quantify production potential based on land availability, land suitability, biomass yield, and cost. We developed such a method and applied it throughout New York State. While maintaining existing forest and agricultural production, we quantified additional sustainable biomass production potential using geospatial and yield modeling that integrates remotely sensed and survey data for land cover, soil type, climate patterns, and crop yields and then applied multiple sustainability constraints. Nearly 680,000 ha with varying quality was found to be available and suitable for new biomass production. Predicted yields ranged from 7.8 to 18.3 Mg/ha for short-rotation willow and 6.9–16.3 Mg/ha for perennial grasses for a total production potential of 8.2 Tg/year. Increased forest harvest could produce an additional 4.3 Tg/year of hardwood and 1.6 Tg/year of softwood. In total, an additional 14.2 Tg/year of biomass for bioenergy could be produced while maintaining existing agricultural and forest production. This new biomass, before processing, would contain energy equivalent to 7.4 % of 2012 New York energy use (3.4 % if converted to ethanol).

Description: Two full-length cDNAs encoding NAM, ATAF, and CUC (NAC)-family transcription factors (TFs) were isolated from two different cultivars of Panicum virgatum L. (switchgrass) and named PvNAC1 and PvNAC2 . Phylogenetic analysis of PvNAC1 and PvNAC2 grouped them with NAC proteins involved in senescence in annual plant species. Transcript profiling revealed that both PvNAC1 and PvNAC2 are induced during leaf senescence. Expression of a PvNAC1-green fluorescent protein (GFP) fusion in plant cells revealed a nuclear location of the protein, consistent with a role in transcriptional regulation. Expression of PvNAC1 in an Arabidopsis nap stay-green mutant suppressed its senescence defect. Expression of PvNAC1 in wild-type Arabidopsis triggered early leaf senescence and remobilization. Transcriptome analysis implicated leaf protein degradation and nitrogen recycling enzymes in NAC-dependent seed protein increase in Arabidopsis . Overexpression of pvNAC2 in switchgrass resulted in increased aboveground biomass associated with increased transcript levels of key nitrogen metabolism genes in leaves and nitrate and ammonium transporter genes in roots. The results indicate that NAC TFs play conserved roles in leaf senescence in the plant kingdom not only in annual monocots and dicots but also in perennial plants such as switchgrass. PvNAC1 and PvNAC2 hold promise for improving nutrient use efficiency in switchgrass through genetic manipulation.

Description: We evaluate how different contract designs impact risk sharing along the supply chain for the dedicated energy crop miscanthus. We model the full production and transportation system of the miscanthus supply chain because a sustainable supply chain must procure biomass in a cost-effective manner. Using this model, we estimate the financial returns and risks for both a farmer producing miscanthus and the biofuels plant purchasing miscanthus. We evaluate differences among contracts that are designed to address the miscanthus investment cost and the farmers’ opportunity costs. We find that risk can be reduced to both the farmer and the plant by offering a dollar per acre base payment combined with a dollar per ton payment. The farmer faces the lowest risk when the contract combines a dollar per acre and dollar per ton payment. Lastly, we find that indexed contracts designed to reduce annual counter-party risk associated with the risk of farmers opting out of the contract to produce competing crops actually increases overall financial risk to the farmer and plant.

Description: This study evaluates the economic viability of using corn to supplement sugarcane for ethanol production in Brazil. Volatility of input and output prices and their correlation due to the transmission of shocks across markets is considered in calculations of Net Present Value. Investment in a flexible mill (i.e. a mill that can process corn during the sugarcane off-season) is dominated by investment in a standard mill based on a second order stochastic dominance criterion. The latter suggests that risk-neutral and risk-averse investors may refrain from investing in a flexible plant. Downside risk associated with a flexible plant may be worsen by the US ethanol blend wall as this weakens the correlation between the price of corn and the price of inputs and outputs of the sugar complex. Reductions in capital import tariffs can offset this effect.

Description: Nutrients in dairy wastewaters can be remediated through assimilation into algal biomass. Anaerobically digested manure creates an effluent (ADE) that is useful for algal cultivation while alternate processing of manure through a polyhydroxyalkanoate reactor generates a distinct effluent (PHAE), not previously characterized for algal cultivation. Each effluent was evaluated for growth rate, biomass production, and nutrient recovery using type algae species Chlorella vulgaris . Growth rates were elevated in 5, 10, and 20 % dilutions of PHAE (0.59, 0.53, 0.42 days −1 ) compared to equal concentrations of ADE (0.40, 0.36, 0.37 days −1 ). In addition, the growth phase lasted up to twice as long for PHAE, resulting in a fourfold higher stationary phase algal concentration (cells∙mL −1 ) compared to ADE. Growth in ADE was limited by specific inhibitory properties: high concentrations of dissolved organic matter, ammonia, and elevated bacterial load. Maximum nutrient removal rates for ADE and PHAE were 0.95 and 3.46 mg·L −1 ·day −1 for nitrogen and 0.67 and 0.04 mg·L −1 ·day −1 for phosphorus, respectively. Finally, biomass derived from PHAE was higher in lipids (11.3 % versus 7.2 %) and thus has a greater potential as a feedstock for biofuel compared to ADE.

Description: Understanding the characteristics of short rotation woody crops (SRWC), like shrub willow, that affect feedstock quality and its variability is a priority as this source of biomass is expanded. Because of its relationship to ash content, the allotment of bark and wood within the stem is often highlighted as a factor impacting feedstock quality. Bark-to-wood ratios are frequently determined in willow by measuring this ratio for the centroid and assuming it represents the entire stem. The objectives of this study were to determine how site and genetic factors influenced the allometry of whole stem bark (WSB%) content on a dry weight basis and if the centroid bark percentage (CB%) on a dry weight basis adequately represents WSB%. A multiple linear regression approach was used to model WSB% and centroid bark content (CB%) using diameter, cultivar, and site factors. Five candidate models were evaluated ranging from parsimonious to complex. The simplest models estimated WSB% from CB% ( R 2  = 0.76) and stem diameter ( R 2  = 0.44). The most complex model included all factors and had an R 2 of 0.90. Two key relationships demonstrated by several models are that (1) CB% adequately predicts but underestimates WSB%, particularly for larger stems, and (2) WSB% increases as diameter decreases. However, empirical models can be enhanced with the inclusion of diameter, site, and cultivar information. The overall approaches can be useful for making relative comparisons between cultivars and sites. In a 3-year-old stand of willow stems less than 20 mm had high WSB%, the maximum being 23.8 %, but accounted for only 5 to 15 % of the total biomass. Large diameter stems accounted for the majority of the total and bark biomass, but the WSB% in large diameter stems is as low as 11.5 %. WSB% ranged from 12.9 to 14 % across the two cultivars at the stand level.

Description: Two-pass harvesting of short-rotation forestry plantations offers the opportunity to accumulate large biomass stores without occupying costly industrial areas, while letting the biomass dry before comminution. This study aimed at developing a simple model for predicting moisture content reduction of short-rotation forestry poplar stems felled and windrowed in the field. In a controlled experiment, cut stem windrows were built and left in the field for up to 6 months (from early December to early June). Thus stored, poplar stems incurred a reduction of moisture content between 10 and 20 percent points. Drying rate varied with the period of storage, and it was faster for later felling dates. Precipitation accounted for 20 to 40 % of the drying rate. No dry matter losses due to microbial activity were recorded during the whole storage period, lasting up to 6 months. The models developed with this study are simple and robust, and allow precision management of collection operations in order to guarantee a constant flow of biomass to user plants.

Description: There is an important need to assess biomass recalcitrance in large populations of both natural and transgenic plants to identify promising candidates for lignocellulosic biofuel production. In order to properly test and optimize parameters for biofuel production, the starting sugar content must be known to calculate percent sugar yield and conversion efficiencies. Pyrolysis molecular beam mass spectrometry (py-MBMS) has been used as a high-throughput method for determination of lignin content and structure, and this report demonstrates its applicability for determining glucose, xylose, arabinose, galactose, and mannose content in biomass. Biomass from conifers, hardwoods, and herbaceous species were used to create a 44 sample partial least squares (PLS) regression models of py-MBMS spectra-based sugar estimates on high-performance liquid chromatography (HPLC) sugar content data. The total sugar py-MBMS regression model had a R 2 of 0.91 with a 0.17 mg/mg root mean square error of validation indicating accurate estimation of total sugar content for a range of biomass types. Models were validated using eight independent biomass samples from multiple species, with predictions falling within errors of the HPLC data. With a data collection time of 1.5 min per sample, py-MBMS serves as a rapid high-throughput method for quantifying sugar content in biomass.

Description: The design of site-adapted biogas cropping systems that combine high methane yield and low environmental impact represents a major challenge for biogas production. A 2-year field experiment was conducted at Hohenschulen, northern Germany, to quantify the nitrate leaching potential and the ecological efficiency, in terms of nitrate-N load per megaliter methane produced, of three maize-based biogas cropping systems: continuous maize (CS1), maize-whole-crop wheat followed by Italian ryegrass as catch crop (CS2), and maize-grain wheat followed by mustard as catch crop (CS3). Crops were fertilized with different levels of digestate, liquid pig manure, or mineral N fertilizer. Leachate was simulated using a plant-soil model, and the nitrate-N load was obtained as the product of measured nitrate-N concentration and the amount of simulated drainage. Regression functions quantifying the relations between nitrate-N load or ecological efficiency and total N input revealed a lower potential nitrate load for CS2 than CS1 and CS3. This indicates a less severe trade-off between methane yield and water pollution for CS2. At the N input required for maximum yield, however, CS1 resulted in lower or similar nitrate-N load than CS2 and CS3. A similar pattern was detected for ecological efficiency, which varied between 2.8 and 6.3 kg nitrate-N (megaliter CH 4 ) −1 . Mineral N fertilizer resulted in higher nitrate-N load than digestate and liquid pig manure for a given total N input. Liquid pig manure tended to cause higher nitrate-N load and lower ecological efficiency than digestate, but differences were not significant. Potential environmental benefits from biogas production can be counteracted by adverse environmental impacts such as the pollution of water bodies. The results of the short-term study suggest that choosing the appropriate N source and N rate is more important than maize cropping system selection in maximizing ecological efficiency.

Description: The underlying aim of biomass crops is to combine high yields and low nutrient contents. Delayed harvests of perennial grasses can reduce nutrient concentrations, while higher levels are generally observed at early harvests. However, depending on the supply chain and the conversion technology, harvesting before senescence could be viable, leading to multiple harvesting, improved feedstock digestibility, and wet biomass storage. In this study, the influence of harvest time and frequency of giant reed ( Arundo donax L.) was assessed on aboveground nitrogen, phosphorus, and potassium concentrations, removal, and nutrient use efficiency. In order to evaluate the effects of different cutting regimes, three single harvest (SH) and six double harvest systems (DH) were compared. Nutrient concentrations declined over the season from 10.3 to 2.5 gN kg −1 , from 1.8 to 0.8 gP kg −1 , and from 30.0 to 8.2 gK kg −1 . Overall, DH led to higher nutrient concentrations than SH. Biomass at second cut tended to be richer in nutrients when harvested in autumn compared with winter, and when first cuts were delayed. Nutrient removal was markedly higher in DH for all the elements considered (on average, 196 kgN, 43 kgP, 530 kgK ha −1 in DH, 111 kgN, 29 kgP, 297 kg Kha −1 in SH). In DH systems, nitrogen and potassium use efficiencies were nearly halved compared with single late cuts, while phosphorus use efficiency decreased by about 30 %. The high nutrient removal rates of double-cut management suggest that it may be not sustainable, unless nutrient cycles are closed and nitrogen losses are evaluated.

Description: Biofuels and bio-based products can be produced from a wide variety of herbaceous feedstocks. To supply enough biomass to meet the needs of a new bio-based economy, a suite of dedicated biomass species must be developed to accommodate a range of growing environments throughout the USA. Researchers from the US Department of Agriculture’s Agricultural Research Service (USDA-ARS) and collaborators associated with the USDA Regional Biomass Research Centers have made major progress in understanding the genetics of switchgrass, sorghum, and other grass species and have begun to use this knowledge to develop new cultivars with high yields and appropriate traits for efficient conversion to bio-based products. Plant geneticists and breeders have discovered genes that reduce recalcitrance for biochemical conversion to ethanol and drop-in fuels. Progress has also been made in finding genes that improve production under biotic and abiotic stress from diseases, pests, and climatic variations.

Description: Sustainable bioenergy crops must contribute not only to the production of renewable energy but also to maintaining or restoring water resource and quality. The aim of this study was to quantify water drainage and nitrate leaching under perennial ( Miscanthus  ×  giganteus and switchgrass), “semi-perennial” (fescue and alfalfa) and annual (sorghum and triticale) bioenergy crops managed with two N fertilisation rates. Soil water and mineral N contents were measured twice a year during 7 consecutive years. These measurements were used to initialize the STICS model which simulated in turn the amounts of drained water and nitrate leached below 210 cm. Semi-perennial crops produced less drainage than annual crops (64 vs. 133 mm year −1 ) despite a similar biomass production. Perennial crops resulted in an intermediate drainage (90 mm year −1 ) but a greater biomass production. The drainage was negatively correlated with biomass production for perennial and annual crops. Perennial crops exhibited much higher water use efficiency than the other species. Nitrate concentration in drained water was low for all crops, most often less than 20 mg NO 3 l −1 . It was lower for perennials than other crops, except for miscanthus on the first year of measurement. However, the comparison of model outputs with nitrate concentrations measured in subsoil after 5 years indicated that the peak of nitrate produced after miscanthus establishment was subsequently recovered by the crop in deep layers (below 210 cm). Perennial bioenergy crops have potential for restoring water quality but may decrease groundwater recharge in deep soils or dry climates.

Description: Alkaline flocculation could be an attractive microalgae harvesting method, because it is low-cost, low energy consumption, and non-toxic to microalgal cells, and the high pH effectively sterilizes the microalgal biomass as well as the process water. In this paper, the mechanism of alkaline flocculation process and the difference between the two strains marine diatom Chaetoceros muelleri #862 and freshwater algae Scenedesmus quadricauda #507 were analyzed. The particle size of C. muelleri #862 cells increased linearly with the increasing pH value which increased dramatically by nearly fivefolds after alkaline flocculation. When pH was below 10.5, the absolute value of zeta potential on the surface of C. muelleri #862 increased rapidly, and also the conductivity of the solution declined quickly. The alkaline flocculation of C. muelleri #862 was mainly attributed to the production of Mg(OH) 2 rather than calcium phosphate or calcium hydroxide. For the strain S. quadricauda #507, the cells still existed integrally as normal cells after alkaline flocculation. Firstly, with the increasing of pH in the solution, the absolute value of zeta potential had not declined. When pH was around 10.8, the absolute value of zeta potential had declined abruptly and the solution conductivity was increasing all the time. The cell wall of S. quadricauda #507 with the high content of cellulose Iα and low crystallization degree was good for the next step of saccharification or oil extraction.

Description: Although sulla ( Hedysarum coronarium L.) has many interesting features that could support the production of biofuels (e.g., a high yield and soluble sugar content, N-fixation capacity, low input requirements for its cultivation), no study has assessed the possibility of its use for that purpose. Our objective was to evaluate the potential value for energy production of sulla cut at various stages of growth. Furthermore, the potential of sulla as a dual purpose crop (energy and feed) was investigated. The crop was grown in rainfed conditions in a typical Mediterranean environment (over two complete 2-year crop cycles) and was cut at four different phenological stages. The biomass was divided into two fractions (stems and leaves), weighed, and analyzed to estimate the theoretical production of bioethanol and biomethane and the feed value of the whole biomass and of the two fractions. The total dry matter yield in the 2-year crop cycle was about 18 Mg ha −1 ; this level of production is similar to or higher than that of most other crops grown in the same environment in rainfed conditions. The stems had a high content of total soluble sugars (even higher than 200 g kg −1 ) and cell wall polysaccharides, markedly higher than the leaves. The leaves contained most of the protein of the plant, representing an actual protein concentrate. Thus, the crop seems particularly suitable for dual purpose use if stems are allocated to the production of biofuels and leaves to the production of livestock feed. Moreover, the results showed that the early seed set stage is the most appropriate cutting time for maximizing yield both for energy and for livestock use.

Description: Valorization of each component of lignocellulosic biomass is critical for sustainability of biorefinery industries. Current biorefineries are confined to ethanol-centric processes and focus only on the carbohydrate-derived sugar using energy-intensive pretreatment methods, leading to deteriorated lignin quality for high-value applications. Organosolv fractionation is an effective method to improve hydrolysis efficiency of cellulose and extract a good quality lignin stream; however, hemicelluloses recovery is challenging if an acid catalyst is used. An alkali catalyst in the organosolv process, therefore, could be a promising alternative approach. We evaluated various organic solvents (glycerol, 2,3-butanediol, dimethyl sulfoxide, ethanol, butanol, isopropanol, acetonitrile, and water) for pretreatment of different biomass feedstocks, including corn stover (grass), poplar (hardwood), and Douglas fir (softwood) using sodium hydroxide as a catalyst. Results showed that an ethanol and isopropanol mixture led to 18 % more sugar released per gram of biomass than the control (conventional aqueous alkali pretreatment) for corn stover; a mixture of ethanol, butanol, and water was the next most effective solvent. For pretreatment of poplar biomass, glycerol and 2,3-butanediol were the most efficient solvents; glycerol pretreatment offers further process improvement opportunities. The organic solvents used in this experiment were not effective for Douglas fir. The quality of released sugars was statistically equal to that of synthetic sugars for 2,3-butanediol fermentation using Klebsiella oxytoca . This study opened up a promising route for high value application for all biomass components. Further research is needed to characterize the extracted lignin for quality evaluation.

Description: In French West Indies, the high dependency of the electricity mix on imported fossil fuels has led local authorities to propose the conversion of some land to the production of energy cane. This conversion mainly concerns land polluted by the pesticide chlordecone, where most crops for human consumption have been banned. This molecule has a strong affinity for soil organic matter (SOM). The aims of this study were to assess the impact of crop residue management and compost application on the stocks of SOM and chlordecone in soils cultivated with energy cane and to determine the minimum SOM input required to maintain SOM stocks. A field experiment was conducted to determine the yield and biomass partitioning of energy cane, and laboratory incubations were performed to estimate humification from crop residues. Changes in SOM and chlordecone stocks over a 30-year period were investigated using models already calibrated for the land under study. Non-harvestable biomass left on the field (tops, litterfall and roots) covered 〉60 % of SOM mineralization. A full offset of mineralization required the return of 10 % of harvestable biomass or the application of compost at a rate of 40 Mg ha −1 every 5 years. With the total removal of harvestable biomass and without compost applications, SOM and chlordecone losses increased by 23 and 13 %, respectively, which was associated with high SOM mineralization and chlordecone leaching under tropical climate. The estimated break-even price for cane biomass indicated that compost application would be more profitable for farmers than the return of a part of the harvestable biomass.

Description: 〈h3〉Abstract〈/h3〉 〈p〉Short rotation coppice (SRC) plantations are predominantly established as monocultures. Reasons include simplicity and thus efficiency in planting, homogeneous growth, and a desire to maximize yields by selecting top-performing species. However, pests and disease outbreaks generally cause much greater damage to monocultures than to mixed plantations, thus affecting yields as well as other ecosystem services. Mixed SRC with varying genotypes or even species have the potential to positively affect biodiversity and ecosystem services, however, little is known about the quantity and quality of woody biomass from mixed SRC in respect to its use for energy generation. Therefore, we tested how volume, calorific value, and ash content of woody biomass are influenced by (1) diversity in genotypes in a 〈em〉Salix〈/em〉 SRC, and (2) diversity of species in a 〈em〉Salix〈/em〉, 〈em〉Robinia〈/em〉, 〈em〉Paulownia〈/em〉, and 〈em〉Populus〈/em〉 SRC. Results show that increasing the number of genotypes or species in a SRC plantation does not negatively affect woody biomass, calorific value, or ash content of wood chips. On average, the plots with mixed genotypes or tree species produced more biomass compared with monocultures of the component species. We found evidence of overyielding in mixtures of poplar and robinia. Our findings are relevant for managers planning new SRC plantations and indicated that mixtures of specific tree species or genotypes should be considered. Therefore, we argue that “high-diversity SRC” plantations represent a valuable alternative to conventional SRC for sustainable bioenergy production.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Various fiber lengths of banana pseudo-stem bagasse (〈em〉L〈/em〉 = 3 and 15 cm) were dehydrated at various temperatures (〈em〉T〈/em〉 = 50 °C, 60 °C, and 70 °C) with and without forced air convection (〈em〉S〈/em〉〈sub〉air〈/sub〉 〉 0). The experiments were conducted in a screened bottom tray equipped with a dryer with rising air flow. The effect of dehydrated fiber size (30 mesh, 3 cm, and 15 cm) on the saccharification of the biomass with subsequent alcoholic fermentation of the must was investigated using two different concentrations of reducing sugars (RS = 40 and 90 g/L). In the pretreatment by drying, the temperature (〈em〉T〈/em〉) was the variable that showed the greatest effect on the productivity of the process (〈em〉Q〈/em〉〈sub〉d〈/sub〉), followed by fiber length (〈em〉L〈/em〉) and 〈em〉T〈/em〉 by 〈em〉L〈/em〉 interaction. The use of dehydrated fibers in the form of bran (30 mesh granulometry) in the saccharification process provided the best theoretical average yield based on the stoichiometric conversion of cellulose and hemicellulose in RS (〈em〉Y〈/em〉〈sub〉RS〈/sub〉 = 37.87%). Fermentation of concentrated must by 〈em〉Saccharomyces cerevisiae〈/em〉 up to RS = 90 g/L provided a yield (〈em〉Y〈/em〉〈sub〉P/RS〈/sub〉) and productivity (〈em〉Q〈/em〉〈sub〉P〈/sub〉) in ethanol of 0.48 g/g and 1.62 g/L/h, respectively. These values were significantly higher (〈em〉p〈/em〉 〈 0.05) than those observed in the same fermentation type at RS = 40 g/L (〈em〉Y〈/em〉〈sub〉P/RS〈/sub〉 = 0.34 g/g, 〈em〉Q〈/em〉〈sub〉P〈/sub〉 = 0.96 g/L/h).〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this work, a sulfated titanium dioxide (STi) catalyst obtained from a commercial TiO〈sub〉2〈/sub〉 precursor was synthesized and characterized. The catalyst was sulfated by the simple impregnation method with H〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉 and subsequently calcined at different temperatures. The synthesized catalyst was characterized by X-ray Diffraction (XRD), Energy-Dispersive Spectroscopy (EDS), and Scanning Electron Microscopy (SEM). The sulfated catalyst was thermally treated at different temperatures (100, 200, 400, and 600 °C) and evaluated in oleic acid esterification reactions by varying the concentration of the catalyst during the conversion of oleic acid to methyl oleate. The conversion was measured from the variation of the acid index (AI)° and free fatty acids (FFA) during the reaction. The STi catalyst obtained was compared with two homogeneous catalysts, H〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉 and ferric sulfate [Fe〈sub〉2〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉3〈/sub〉], evaluating the reaction time in the conversion, from which improvements in the reaction performance of the catalyst synthesized in this work were observed versus the two homogeneous catalysts mentioned earlier. Catalyst reuse cycles were also evaluated as well as their performance in the esterification of waste cooking oil. The best catalyst yields reached values close to 86% in a reaction time of 6 h.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Straw removal for bioelectricity, cellulosic ethanol, or other bio-products has become a common practice in Brazilian sugarcane areas, but long-term effects on soil organic carbon (SOC) and yield are unknown. Our objective was to quantify tillage intensity and removal levels on SOC stocks and sugarcane yield on contrasting edaphoclimatic conditions in Brazil. Conventional tillage-CT and reduced tillage-RT coupled with three straw removal levels (none—NR; moderate—MR; total—TR) were combined to create six treatment combinations: CTNR, CTMR, CTTR, RTNR, RTMR, and RTTR, respectively. Sugarcane yield was measured annually and soil samples to a depth of 40 cm were collected and analyzed before and after 5 years of treatments. Neither tillage practices nor straw removal significantly affected sugarcane yield on sandy loam soil, but CTMR, CTTR, and RTTR showed substantial yield reductions on clayey soil. SOC stocks for RTNR increased by as much as 1.64 Mg ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉 on clayey soil, while CTMR and CTTR favored depletion of SOC stocks on both soils. Overall, each Mg of straw returned to the soil increased SOC stock by 95 kg ha〈sup〉−1〈/sup〉 for clayey soil under both tillage practices and 55 kg ha〈sup〉−1〈/sup〉 for sandy loam under the CT system. Furthermore, straw removal decreased microbial biomass C and b-glucosidase activity. These findings suggest that the adoption of RT attenuates the adverse impacts of straw removal on SOC stocks while ensuring sugarcane yields for a more sustainable bioenergy production in Brazil.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Rice straw was sequentially pre-treated with sulphuric acid (3% 〈em〉v〈/em〉/〈em〉v〈/em〉) and sodium hydroxide (4% 〈em〉w〈/em〉/〈em〉v〈/em〉) which resulted in the removal of ~ 90% hemicelluloses and ~ 55% lignin, respectively. The pre-treated rice straw was saccharified with cellulases to produce 787 mg/g reducing sugars, which were further fermented with 〈em〉Saccharomyces cerevisae〈/em〉 HAU. The acid hydrolysate produced after acid treatment was also subjected to fermentation by 〈em〉Pichia stipitis〈/em〉 NCIM 3499. The hexose and pentose fermentation leads to production of 26.9 g/L and 9.4 g/L of ethanol (79% and 93% fermentation efficiency, respectively). High purity (98%) lignin (146 mg/g dry substrate) was precipitated by direct acidification with HCl from the spent liquor obtained after alkali treatment. Extracted lignin was characterized by FTIR and TGA. Overall, the study aimed at effective utilization of all major polymers of rice straw into valuable products making the bioethanol production process more sustainable.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Physiological susceptibility to early- and late-season chilling limits commercial production of sugarcane (〈em〉Saccharum〈/em〉 spp. hybrid), a major crop for lignocellulosic biomass, refined sugar, and bioethanol, to tropical and the warmest subtropical regions. Interspecific and intergeneric hybridization have been used to broaden the genetic base of sugarcane and improve its adaptation to temperate climates. Chilling tolerance can be introgressed in sugarcane through intergeneric hybridization with 〈em〉Miscanthus〈/em〉, a cold-tolerant C〈sub〉4〈/sub〉 perennial grass, which is genetically homologous to sugarcane. This study evaluated intergeneric F〈sub〉1〈/sub〉 hybrids of 〈em〉Saccharum〈/em〉 × 〈em〉Miscanthus〈/em〉, miscanes, which included two genotypes of sugarcane × 〈em〉Miscanthus sinensis〈/em〉 and sixteen genotypes of sugarcane × 〈em〉Miscanthus sacchariflorus〈/em〉, for their seasonal variation in photosynthesis and biomass production under field conditions in Hokkaido, Japan, to identify promising genotypes and traits, which can be selected to further improve sugarcane. Results showed several of the miscane genotypes had high early- and late-season photosynthesis coupled with high biomass production, which likely indicates chilling tolerance. High broad-sense heritabilities for traits, including stem diameter, tiller number, leaf width, leaf and stem dry weight, and high correlations between these traits and dry matter yield indicate selections can be made efficiently to improve sugarcane. Although none of the miscanes overwintered at the experimental location, we identified miscane “JM 14-09” as a superior genotype for introgression breeding programs and as a potential energycane cultivar for its high biomass-production capacity.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Microalgae have been appeared as excellent source of bioenergy recently in Brunei Darussalam due to the favorable growth conditions, while sewage sludge emerged as major threat to the environment. Therefore, the challenge of sewage sludge management and microalgae utilization has spurred the demand of developing an innovative approach to utilize these sources for commercial applications. Hence, the main objective of this study was to characterize the bioenergy properties of microalgae, sewage sludge, and different blending ratios of microalgae-sewage sludge incorporated with sub-bituminous coal. Among three different blended samples, sample mixture 1 (SM-1) combined with 25% microalgae, 25% sewage sludge, and 50% coal presented the highest calorific value of 16.57 MJ/kg and lowest ash content of 45.61%. Along with this, SM-1 also manifested the highest values for pellet density (1.23 g/cm〈sup〉3〈/sup〉) and energy density (20.41 GJ/m〈sup〉3〈/sup〉) that can be referred as the most favorable values among all co-pelletized samples for transportation and logistics. Besides the characterization of raw samples, this study also emphasized on elemental analysis of ash content to determine the possibility of fouling and slugging. Ash analysis of all blends represented the major inorganic components aluminum (Al) and silicon (Si). Thermogravimetric analysis of all samples demonstrated the different phases of pyrolysis and combustion within 50 to 900 °C at heating rate of 10 °C/min. It can be concluded that this study recommended SM-1 as a potential feedstock for solid fuel purpose.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Restricted activities of individual plant cell wall–degrading enzymes, i.e., cellulase, xylanase, and pectinase, on plant biomass are due to the complex interactions among structural polysaccharides and lignin components of plant cell wall. This can be overcome through altering the structural components by subjecting biomass to physicochemical pretreatments. In present studies, experiments were undertaken with the rationale that applying tailor-made cocktail formulations to pretreated biomass, by striking a synergy between core cellulolytic (C) and/or accessory xylano-pectinolytic (X, P) enzymes from the 〈em〉Bacillus〈/em〉 strains 〈em〉B. safensis〈/em〉 M35, 〈em〉B. altitudinis〈/em〉 R31 and 〈em〉B. altitudinis〈/em〉 J208, should enhance the saccharification. Efficiency of individual and substitutive cocktails for saccharification of raw, NaOH, and NH〈sub〉4〈/sub〉OH pretreated sugarcane bagasse was demonstrated and compared. Among the individual CP, CX, PX, and CPX cocktails, the CPX cocktails yielded enhanced and maximum saccharification of 71.4–81.3% and 17.0–17.28% from NaOH and NH〈sub〉4〈/sub〉OH pretreated biomass as compared to the 7.1–7.6% from raw. After finding xylanases and pectinases from the three 〈em〉Bacillus〈/em〉 strains compatible with each other, substitutive cocktail CPX〈sub〉sub〈/sub〉 was prepared by putting all these accessory enzymes with core cellulase. This enhanced saccharification to 84.02% and 25.52% from NaOH and NH〈sub〉4〈/sub〉OH pretreated biomass as compared to 8.91% from raw. With the support of HPLC, FTIR, and SEM analyses, results clearly confirmed the high saccharifying potential of tailor-made substitutive cocktails due to synergistic and accessory nature of xylanases and pectinases to the core commercial cellulase.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Brazil has the world’s second largest cattle herd, which produces 1.9 billion tons of cattle manure per year. This work describes, for the first time, the processing of cattle manure by pyrolysis at 400, 500, and 600 °C in a rotary kiln reactor, as an alternative means of treating this waste to produce second generation biofuels. The biomass was mainly composed of hemicellulose (18.24%), cellulose (14.24%), and lignin (6.09%), with high ash content (18.86%). Pyrolysis of the cattle manure at 500 °C resulted in the best bio-oil yield (5.8% organic phase; 34.4% aqueous phase). The bio-oil consisted mainly of phenolic compounds such as phenol and 3-vinyl-phenol. The results for the biochar were indicative of its potential use in agricultural applications for correcting soil acidity. The biochars produced at higher temperatures presented a high degree of aromaticity, indicating the formation of a more stable material for the purposes of carbon sequestration.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Sugarcane (〈em〉Saccharum officinarum〈/em〉) residue (straw) has been identified as a promising feedstock for bioenergy production, but excessive straw removal may impair soil macrofauna and related ecosystem services. To quantify straw removal effects on abundance, richness, and diversity of soil macrofauna, four experiments were conducted in São Paulo state, Brazil, under different edaphoclimatic conditions. A secondary goal was to evaluate seasonal changes on soil macrofauna and identify linkages between those changes and soil chemical and physical attributes. Four straw removal treatments (NR, no removal, LR, low removal, HR, high removal, and TR, total removal) were evaluated. Macrofauna and other soil attributes were sampled within the 0- to 0.30-m depth increment. Soil macrofauna were impaired by TR with the magnitude of response being related to both edaphoclimatic conditions and management practices. Numerous interactions among seasons, straw removal rates, and soil macrofauna were found, especially for total abundance and diversity of organisms. Partial straw removal (HR and LR) may be a strategy to protect soil health and increase bioenergy production with minimal effects on soil macrofauna, although long-term experiments are needed to confirm our hypothesis. The NR treatment generally had better soil quality as indicated by greater soil moisture, macropore number, soil organic carbon (SOC) content, and soil fertility, which led to a higher abundance of most macrofauna organisms. Total removal resulted in greater soil compaction and decreased macrofauna abundance, especially in clay soils. Our findings confirm that an integrated approach using soil indicators as guidelines should be adopted to better predict sustainable straw management practices for sugarcane in Brazil.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉High demand for crop oils is anticipated in the lubricant industry because of their renewable, non-toxic, environment-friendly nature. Crop oils typically offer high viscosities, viscosity indexes, and flashpoints. The unique structure of crop oils provides good lubrication, high flammability, and anti-corrosion ability. In contrast, petroleum-based lubricants face a difficult future because of declining petroleum reservoirs that will increase their prices. This paper reviews green-lubricant feedstock requirements, the effect of fatty acids composition to improve physicochemical properties, chemical modifications of green lubricants by applying transesterification to find suitable environmentally -friendly and cheaper feedstock to replace petroleum lubricants. Moreover, global and Pakistani indigenous crop oils are also analyzed for their potential use in green lubricants by comparing their fatty acid compositions, characteristics and reaction conditions according to applications and standards. This review discovers that cottonseed oil has great potential as a new sustainable and cheaper feedstock for the global and Pakistani green-lubricant markets. Green lubricant production rate can be enhanced significantly after upgrading the conventional production method. It is believed that this review paper will provide useful information to engineers, researchers, chemists, industrialists, and policymakers, who are interested in green-lubricants synthesis.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The large-scale culture of microalgae has become a focus of interest for the biorefinery industry, combining the production of biofuels with that of other value-added bioproducts and thus increasing the profitability of the process. In order to evaluate its potential as biodiesel feedstock under a biorefinery approach, the biomass, pigment, nutrient, total lipid and lipid fraction kinetics of the Argentinian 〈em〉Nannochloropsis oceanica〈/em〉 CCALA 978 strain were analysed. The species was first cultivated under optimal conditions (f/2 medium) and then transferred to nutritional stress conditions (N-deprivation or P-deprivation media). Under complete f/2 medium, 〈em〉N. oceanica〈/em〉 presented maximum growth rate (〈em〉μ〈/em〉) and chlorophyll-〈em〉a〈/em〉 values and minimum values for lipid and carotenoid content. The high nutrient consumption rate (N or P) in this exponential phase was associated with increasing cell density. Under both nitrate and phosphate deprivation, 〈em〉μ〈/em〉 was drastically reduced but biomass production reached its highest values, indicating a phase of metabolite accumulation. Maximum values of total lipids (ca. 39% dw) and carotenoids (1100 × 10〈sup〉−3〈/sup〉 ± 15 μg mL〈sup〉−1〈/sup〉) were obtained under nitrate deprivation. In addition, total lipid composition was characterized by 92% neutral lipids, 0.7% phospholipids, a high percentage of C16:1 (ca. 37% of total fatty acids) and minimum values of PUFA (5.9% of total fatty acids). Biodiesel properties inferred from the fatty acid methyl ester profile of neutral lipids meet the standards established by EN 14214 and ASTMD 6751-08. Although N and P deficiency both produced an increase in neutral lipids in the studied strain, under a biorefinery approach, nitrate deprivation is considered to be a better method of stress induction than phosphate deprivation for the purpose of co-producing neutral lipids for biodiesel and value-added pigments.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉About 11% of the world’s primary energy consumption comes from biomass. However, a continuing material deficit indicates the need to find suitable timber for use as bioenergy. In this context, this study aims to determine some chemical and energetic properties, wood density, and fiber features of 10 〈em〉Hevea brasiliensis〈/em〉 clones, including 〈em〉Eucalyptus tereticornis〈/em〉 and 〈em〉E. pellita〈/em〉 species, to understand how the characteristics of studied woods might interfere with higher heating value (HHV) and determine if these woods and their residues would present potential for bioenergy. In general, HHV results corroborate those in the literature, e.g., 〈em〉E. pellita〈/em〉 (16,502 kJ kg〈sup〉−1〈/sup〉) lower value, and MT45 〈em〉H. brasiliensis〈/em〉 clone (19,757 kJ kg〈sup〉−1〈/sup〉) higher value, and woods with higher extractive contents and lignin content, but lower holocellulose content, of wood pulp, in addition to denser woods with longer fibers and thicker walls, are woods considered to have higher heating values and, hence, indicated as potential woods for use in bioenergy. However, it is suggested that wood characteristics should be analyzed together to determine the most suitable material for use in bioenergy since a high value of one factor influencing HHV would not, in and of itself, establish suitability of the wood for bioenergy. Nonetheless, all wood samples could have their waste exploited for bioenergy since they range from 16,502 kJ kg〈sup〉−1〈/sup〉 in 〈em〉E. pellita〈/em〉 to 19,757 kJ kg〈sup〉−1〈/sup〉 in the MT45 clone of 〈em〉H. brasiliensis〈/em〉.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study focused on relationships between soil properties, root architecture, and aboveground biomass productivity of 〈em〉Salix miyabeana〈/em〉 “SX67”. Roots were excavated at eight short-rotation cultures with contrasted soil/climatic conditions and root system ages from 4 to 14 years. The depth of the root branching points to the initial cuttings, root diameters, and root branching occurrence as well as soil physico-chemical properties were measured. Aboveground biomass had been estimated in a previous study, which allowed to calculate a proxy of root-to-shoot ratio. Root system ages and belowground biomass were related (adj. 〈em〉R〈/em〉〈sup〉2〈/sup〉 = 0.88, 〈em〉p〈/em〉 〈 0.001). However, biomass partitioning in the different tree components was mainly governed by soil properties. Sand content was related to root-to-shoot ratio (adj. 〈em〉R〈/em〉〈sup〉2〈/sup〉=0.73, 〈em〉p〈/em〉 〈 0.01) and the proportion of coarse roots (diameter 〉 1 cm) deeper than 10 cm (adj. 〈em〉R〈/em〉〈sup〉2〈/sup〉 = 0.75, 〈em〉p〈/em〉 〈 0.01), whereas clay content was related to root branching occurrence-to-aboveground productivity ratio (adj. 〈em〉R〈/em〉〈sup〉2〈/sup〉 = 0.80, 〈em〉p〈/em〉 〈 0.01). Coarse root depth distribution was related to aboveground biomass following a quadratic model that suggested (〈em〉i〈/em〉) a maximal aboveground biomass productivity when a third of the roots were deeper than 10 cm and (〈em〉ii〈/em〉) two opposite strategies of biomass allocation, i.e., biomass was allocated “downward” with a higher proportion of deeper roots and root-to-shoot ratio at sites with coarser soils and “upward” with a lower proportion of deeper roots and root-to-shoot ratio at sites with clayey/compacted soils. The study highlights how root plasticity of “SX67” copes with different soil stresses to maintain high aboveground biomass productivity.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Five plant species from two Chinese constructed wetland (CW) environments were studied for the production of bioethanol using simultaneous saccharification and fermentation (SSF). Fourteen CW plant species were found in the constructed wetlands and four species (〈em〉Phragmites australis〈/em〉, 〈em〉Fargesia spathacea〈/em〉 F., 〈em〉Thalia dealbata〈/em〉, and 〈em〉Juncus effusus〈/em〉 L.) containing the highest contents of holocellulose (between 50 and 55% d.b.) as well as a highly abundant invasive species (〈em〉Eupatorium adenophorum〈/em〉) were selected for further study of bioethanol production. Among the selected species, 〈em〉P. australis〈/em〉, 〈em〉T. dealbata〈/em〉, and 〈em〉J. effusus〈/em〉 L. exhibited high glucose conversion efficiencies between 42 and 46% of the sample dry mass. These three species were then subjected to SSF at 38 °C with 〈em〉Saccharomyces cerevisiae〈/em〉 BY4742 and obtained ethanol titers between 30 and 35 g/L. These results indicate promise for the application of CW plants in second-generation biofuel production.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Interesterification reaction of palm oil and ethyl acetate for the synthesis of biodiesel was performed in a small-scale fixed-bed reactor. The reactor was packed with ion-exchange resin (RCP160M), which was used as catalyst for this work. The important factors affecting biodiesel content including reaction temperature, mass flow rate of reactants, and ethyl acetate-to-oil molar ratio were examined and optimized via the Box-Behnken design. Main effects and interactions of the variables on biodiesel content were addressed. The remarkable long-term stability of catalyst was also demonstrated for at least 72 h of continuous operation with relatively constant %FAEE. The optimal conditions yielding 99% of ester content were found as follows: reaction temperature of 113 °C, total mass flow rate of 5.4 × 10〈sup〉−4〈/sup〉 kg/h, and ethyl acetate-to-oil molar ratio of 16.7:1. Considering the operating conditions and productivity parameter, this method could be further developed for efficient biodiesel production.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical Abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/12155_2019_10051_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This issue of 〈em〉Bioenergy Research〈/em〉 summarizes the results of two large-scale projects aiming to provide quantitative data to support decision-making for straw management and establish rational plans for sustainable straw removal without compromising soil health, greenhouse gas (GHG) emissions, and sugarcane yield in Brazil. These projects cover results from multi-disciplinary research quantifying the effects of sugarcane straw harvest, transport, and conversion into biofuel, bioelectricity, or bio-renewable. Seventeen publications from a cross-institutional group addressing soil health, nutrient cycling and fertilizer management, GHG emissions, pest management, crop yield, engineering solutions, and industrial performance are included in this special issue. Overall, the main findings confirm that sustainable straw removal is feasible in Brazil, but integrated knowledge should be used to ensure that straw removal for industrial uses will not compromise soil ecosystem services and crop yields. We believe that this special issue provides an amalgamation of high-level scientific information and can be used on a strategic basis by academics, sugarcane industry, and policy makers at both state and national government levels.〈/p〉

Description: 〈p〉The first and last names for both of the authors are reversed.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study proposes a novel integration of a municipal wastewater treatment facility (WWTF) with a cyanobacterial nutrient removal process for sidestream wastewater treatment. A life cycle assessment (LCA) approach was used to determine the effectiveness and environmental performances of the integrated system. The LCA is populated by models of wastewater process engineering, material balance, cyanobacterial growth, and kinetics of anaerobic digestion. The cyanobacteria growth model incorporates chlorophyll synthesis, nitrogen uptake, photosynthesis, centrate inhibition, and competition for nitrogen between cyanobacteria and nitrifiers. Modeling results are validated against experiments with 〈em〉Synechocystis〈/em〉 sp. PCC6803 grown in sludge centrate. With a maximum specific growth rate of 1.09 day〈sup〉−1〈/sup〉, the nitrogen removal rate of the proposed WWTF would be increased by 15% when compared to the baseline wastewater treatment facility with a biological nutrient removal process. Incorporating the cyanobacterial nutrient removal process as the sidestream wastewater treatment of a conventional activated sludge process reduces the total nitrogen concentrations discharged from the WWTF from 25.9 to 15.2 mg 1〈sup〉−1〈/sup〉. Methane yield was found to be increased by 4% of the baseline value when cyanobacterial biomass was co-digested with the activated sludge. Life cycle energy use and greenhouse gas emissions were found to be reduced by 8% and 17%, respectively, relative to a baseline wastewater treatment facility. Overall, a cyanobacteria-based sidestream municipal wastewater treatment process could be an effective and environmentally sustainable biological nutrient removal process in the future addressing the water-energy-food nexus.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This work provides the first study about the evaluation of the bioenergy potential of lignocellulosic waste from Brazilian pine-fruit shell (〈em〉Araucaria angustifolia〈/em〉). Physicochemical characterization, evolved gas from pyrolysis, and kinetic and thermodynamic studies were performed. A thermogravimetric analyzer was used for the pyrolysis experiments, where the runs were performed under an inert atmosphere of nitrogen at temperatures ranging from room temperature to 850 °C at different low heating rates (5, 10, 20, and 30 °C min〈sup〉−1〈/sup〉). The physicochemical characterization of Brazilian pine-fruit shell showed good applicability for the gasification process due to the high fixed carbon content. Similarly, the pyrolysis experiments and FTIR-evolved gas analysis indicate its great potential for use as a solid biofuel. The kinetic study showed that the Kissinger–Akahira–Sunose method (〈em〉ε〈/em〉 = 0.07–0.11%) had a smaller relative error, when compared with the methods of Friedman (〈em〉ε〈/em〉 = 5.12–28.89%), Flynn–Wall–Ozawa (〈em〉ε〈/em〉 = 0.26–1.21%), and Starink (〈em〉ε〈/em〉 = 0.17%), and it was comparable to the Vyazovkin method (〈em〉ε〈/em〉 = 0.08–0.09%). Furthermore, the conversion rate curves obtained from kinetic parameters showed a satisfactory behavior, with a high regression coefficient (〈em〉R〈/em〉〈sup〉2〈/sup〉 ≥ 0.9165), thus demonstrating the great applicability of the parameters for the design and optimization of the thermochemical system. The endothermic and nonspontaneous process was observed, based on the positive Δ〈em〉H〈/em〉, positive Δ〈em〉G〈/em〉, and positive Δ〈em〉S〈/em〉 values of Brazilian pine-fruit shell. The pyrolysis of Brazilian pine-fruit shell has been identified as a viable alternative for bioenergy generation, acting as a solution for the final disposal of this agricultural waste biomass.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Soaking in aqueous ammonia (SAA) is a means of pretreating biomass at moderate temperatures and ammonia concentrations (15% 〈em〉w〈/em〉/〈em〉w〈/em〉). To establish process consistency and scalability, sieved maize stover was pretreated at 50-ml, 300-ml, and 100-l scales. Each scale was carried out through different methods. Sealed reactor tubes were used for 50-ml pretreatment. Fabric dyeing apparatus was used for the 300-ml pretreatment and a commercial Littleford DVT reactor was used for 100-l pretreatment. For each scale, biomass washing and solid-liquid separations were scaled appropriately. Washed pretreated solids were analyzed for composition and recovery of dry biomass and carbohydrates calculated. Nearly 100% of the glucan content was recovered in pretreated solids at all three scales, indicating the viability of SAA pretreatment. Pretreated solids (15% 〈em〉w〈/em〉/〈em〉w〈/em〉) were hydrolyzed in a 1-l twin Sigma blade mixer using Cellic CTec2 (15 FPU.g-glucan〈sup〉−1〈/sup〉) followed by fermentation in shake flasks. Hydrolytic yields ranged 65–70% across scale treatments. In comparison, fermentative yields averaged 95% across scale treatments, indicating saccharification to be a rate-limiting step in effective bioconversion of lignocellulose.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Biodegradation of agribiomass especially wheat straw to biohydrogen and biomethane is an encouraging approach to the current waste management problem. To do so, the biomass must first be pretreated to break down lignin thereby increasing accessibility of the substrate to fermentative organisms. In the current study, out of 20 isolates from the granular sludge of full-scale anaerobic digester, four ligninolytic 〈em〉Bacillus〈/em〉 sp. strains were selected based on their lignin and Azure B degradation. Further, among the four isolates, 〈em〉Brevibacillus agri〈/em〉 AN-3 exhibited the highest of 88.4 and 78.1% decrease in COD of lignin and Azure B respectively. These strains were also found to secrete optimum yields of lignin peroxidase (LiP) at pH 3, laccase (Lac) at pH 5, and xylanase and cellulase enzymes at pH 7. The strains demonstrated maximum activity of Lip and Lac at 50 °C and xylanase and cellulase at 60 °C after 72-h growth. Among the four strains, 〈em〉Brevibacillus agri〈/em〉 AN-3 showed hydrogen (H〈sub〉2〈/sub〉) yield of 1.34 and 2.9 mol-H〈sub〉2〈/sub〉/mol from xylose and cellulose respectively. In two-phase wheat straw batch fermentation, 〈em〉Brevibacillus agri〈/em〉 AN-3 produced 88.3 and 283.7 mL/gVS cumulative H〈sub〉2〈/sub〉 and methane (CH〈sub〉4〈/sub〉) respectively. Biotreatment with ligninolytic 〈em〉Bacillus〈/em〉 sp. strains perceived that 261.4% more methane yield could be obtained from the wheat straw than using the untreated wheat straw in batch fermentation. This is the first study establishing not only the hydrogen potential of ligninolytic 〈em〉Bacillus〈/em〉 sp. strains but also indicates a vital role of these species in developing standard inoculum and a biocatalyst for processing agribiomass.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical Abstract〈/strong〉 〈em〉 〈div〉ᅟ〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/12155_2018_9936_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this study, our working hypothesis was to examine whether temperature alters biomass and metabolite production by microalgae according to strain. We also addressed whether it is possible to choose a strain suitable for growing in each season of a given region. A factorial experiment revealed a significant interaction between chlorophylls 〈em〉a〈/em〉 and 〈em〉b〈/em〉 (Chl 〈em〉a〈/em〉 and Chl 〈em〉b〈/em〉), carotenoid/Chl (〈em〉a〈/em〉 + 〈em〉b〈/em〉) ratio, biomass and total lipid productivity of six green microalgae (four 〈em〉Chlorella〈/em〉 spp., 〈em〉Chlorella sorokiniana〈/em〉 and 〈em〉Neochloris oleoabundans〈/em〉) after 15 days at four temperatures. At 39/35 °C, two 〈em〉Chlorell〈/em〉a sp. strains (IPR7115 and IPR7117) showed higher total carotenoids/Chl (〈em〉a〈/em〉 + 〈em〉b〈/em〉) (0.578 and 0.830), respectively. 〈em〉N. oleoabundans〈/em〉 had the highest Chl 〈em〉a〈/em〉 (8210 μg L〈sup〉−1〈/sup〉) and Chl 〈em〉b〈/em〉 (1909 μg L〈sup〉−1〈/sup〉) at 19/15 °C and highest maximum dry biomass (2900 mg L〈sup〉−1〈/sup〉), specific growth rate (0.538 day〈sup〉−1〈/sup〉) and total lipids (1003 mg L〈sup〉−1〈/sup〉) at 15/8 °C. We applied a method to infer the growth of these six green microalgae in outdoor ponds, as based on their response to changing temperatures and by combining with historical data on day/night air temperature occurrence for a given region. We conclude that the use of regionalized maps based on air temperature is a good strategy for predicting microalgal cultivation in outdoor ponds based on their features and tolerance to changing temperature.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A central composite design circumscribed method was used to define the experimental conditions that improve the methane production rate (〈em〉k〈/em〉〈sub〉CH4〈/sub〉, liters of methane per kilogram of VS of waste added and per day) and the cumulative methane production (cMP, liters of methane per kilogram of VS of waste added) of the co-digestion of sewage sludge (SS) with crude glycerol (cGly) and waste frying oil (WFO). Three factors were selected, i.e., SS concentration, global co-substrate concentration, and mass fraction of cGly (〈em〉x〈/em〉〈sub〉cGly〈/sub〉) in a mixture of cGly and WFO (in chemical oxygen demand, COD). SS digestion without co-substrate reached a cMP of (294 ± 6) L·kg〈sup〉−1〈/sup〉 and a 〈em〉k〈/em〉〈sub〉CH4〈/sub〉 of (64 ± 1) L·kg〈sup〉−1〈/sup〉·d〈sup〉−1〈/sup〉, at standard temperature and pressure conditions and expressed relatively to the initial volatile solids. After statistical analysis, SS and co-substrate concentrations of 4.6 g·L〈sup〉−1〈/sup〉 and 8.8 g·L〈sup〉−1〈/sup〉 (in COD), respectively, with 〈em〉x〈/em〉〈sub〉cGly〈/sub〉 of 0.8, were defined to simultaneously boost cMP (91 % more) and 〈em〉k〈/em〉〈sub〉CH4〈/sub〉 (3-fold increase). Application of these conditions would yield 214 MWh more in electricity per 1000 m〈sup〉3〈/sup〉 of SS digested.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉During the last years, a demand for regionally produced biogas feedstocks was created by government subsidies to biogas production in Germany—contrary to the trend of specialization of agricultural production towards global commodity markets. The question arose whether this trend could contribute to an increased cultivation of uncommon crops and diversification of cropping patterns, owing to comparably different and less restricted feedstock requirements. In the cooperative research project “EVA,” a multi-site experimental crop rotation field trial was conducted over 8 years at eight sites, representing the variety of soil-climatic conditions in Germany. The aim of the trial was to assess a variety of established and novel crops for anaerobic digestion. This paper presents the key findings of the trial. Special emphasis is given to biomass productivity and profitability. The chances for the approach “diversification of cropping patterns via energy cropping” are discussed. Results show that maize (average 4-year dry matter yield varied site-specific between 14.22 and 25.12 t ha〈sup〉−1〈/sup〉) is clearly the most efficient crop for biogas production in Central Europe. Some cropping options for biogas feedstock production, such as winter triticale (whole crop, average yield of 6.71 to 15.17 t ha〈sup〉−1〈/sup〉) or perennial fodder mixtures (average yield of 7.51 to 19.44 t ha〈sup〉−1〈/sup〉) are feasible choices for farmers in some regions, which could contribute to diverse cropping systems.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this study, the effect of sludge retention time (SRT) on biomass production and nutrient removal was determined by constant hydraulic retention time (HRT) with mixed microalgae culture. The SRTs of 2, 3, 6, 12, and 24 days with constant 24 h HRT were studied in microalgae membrane photobioreactor (msMpBR) by using hollow fiber (HF) membranes with a pore diameter of 0.45 μm. According to the results, the best removal was achieved within 3 days of SRT. Chlorophyll-a/mixed liquor suspended solid (MLSS) ratios were found to be 0.033. Total nitrogen (TN) and phosphate phosphorus (PO〈sub〉4〈/sub〉–P) removal rates were found to be 5.55 mg N/L day〈sup〉−1〈/sup〉, and 0.4 mg PO〈sub〉4〈/sub〉–P/L day〈sup〉−1〈/sup〉, respectively. The volumetric microalgae production was found to be 0.118 g/L day〈sup〉−1〈/sup〉. Also, 〈em〉Chaetophora〈/em〉 sp. and 〈em〉Navicula〈/em〉 sp. cultures were found to be dominant in steady state. The percentage of lipid and protein in dry biomass was obtained to be 8.94% and 30.34%, respectively. It is advisable to use algal membrane photobioreactor, and mixed microalgae cultures instead of specific microalgae cultures, which could be readily affected by seasonal changes and outdoor conditions in wastewater treatment.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Fifteen varieties of willow (〈em〉Salix〈/em〉) hybrids were observed in a replicated study on five diverse sites in Michigan during the establishment year and over two subsequent 3-year rotations. Sixty-one percent of the total variation in yield observed was due to environmental factors, 11% was due to genetic factors, and the remainder was unexplained. Biomass yield over 6 years ranged from 50.5 oven-dry Mg ha〈sup〉−1〈/sup〉 at one site to 22.9 oven-dry Mg ha〈sup〉−1〈/sup〉 at another. Warmer and wetter sites tended to produce more biomass than colder drier sites, but correlations between yield and other edaphic and climatic factors were less clear. High-yielding varieties tended to be taller, but survival and number of stems per stool were uncorrelated with yield. A cohort of elite varieties selected based on test-wide performance produced up to 26% more biomass than randomly chosen varieties. Cohorts of elite varieties selected based on performance in local tests did better, producing up to 31% more biomass than randomly chosen varieties. Because of ranking changes, selections made after two rotations outperformed those made after only one rotation by as much as 9%. Adequately tested planting stock has the potential to increase the financial return to a willow energy farmer by nearly $100 ha〈sup〉−1〈/sup〉 year〈sup〉−1〈/sup〉. This will multiply rapidly as willow is planted on some of the 700 million hectares of retired cropland in the USA. The nominal cost of breeding and field testing willow energy crops can be easily justified as we proceed to the envisioned billion-ton bioeconomy.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Variability in biomass yield among 13 varieties of 〈em〉Populus〈/em〉 hybrids was examined during a 7-year rotation in a network of 4 field trials in Michigan, USA. Seventh-year yield varied by site, averaging from 15.1 Mg ha〈sup〉−1〈/sup〉 in the north to 35.2 Mg ha〈sup〉−1〈/sup〉 in the south. Yield varied among varieties, ranging from 3.0 Mg ha〈sup〉−1〈/sup〉 for DN70 in the north to 52.9 Mg ha〈sup〉−1〈/sup〉 for NM2 in the south. Yield was most strongly correlated with growing season temperatures and rainfall but less with edaphic factors throughout the network. Twenty-eight percent of the total variation in individual tree weight was due to location effects and another 28% was due to genetic factors, including strong genotype by environment interactions. Even though each 64-tree plot comprised genetically identical clones, the remaining 44% of total observed variation among trees occurred within these plots. Five varieties that performed well throughout the network were identified as an elite cohort for general commercial use throughout the region. This cohort yielded as much as 50% more biomass than random selections. Certain varieties did well at one location while not at others because of strong genotype by environment interactions. Locally chosen elite cohorts produced as much as 5% more biomass than the regional elite cohort. Varietal ranking did change over time but it was possible to reliably identify the regional cohort after 3 years and local cohorts after 4 years. Local, long-term testing of 〈em〉Populus〈/em〉 hybrids will be necessary to optimize commercial biomass yields and thereby maximize financial returns to growers.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Certain substrate-related parameters that determine sugar release from pretreated lignocellulosic biomass are important for the biorefinery process optimization. Unfortunately, phylogenetical differences in plants often complicate physicochemical variances and mask mechanisms of biomass recalcitrance. Herein, an in-depth statistical approach that combines correlation analysis, principal component analysis, multiple linear regression, and multiscale validation procedures was employed to comprehensively analyze 14 compositional and structural parameters of cell wall collected after acid and base pretreatment. Individual and sequential analysis provided quantitative proof of lignin-relevant parameters as particular constraints for sugar release in two typical plants, the rice straw (〈em〉Oryza sativa〈/em〉) and poplar (〈em〉Populus girinensis〈/em〉). More striking contributions of lignin removal to xylose release were found in both biomasses, while the combination of crystallinity index (CrI) and CrI/glucan highlighted the specific hindrance of crystallinity of cellulose to glucose release. The compositional changes of lignin additionally affected glucose release in rice straw, while functional groups of lignin played a less pronounced role in poplar. The direct impacts of xylan removal and concomitant changes in biomass porosities insignificantly improved the sugar release. These results suggest that innate differences in diverse plants and the targeted sugar species should be considered when designing proper pretreatment for efficient enzymatic hydrolysis.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The bioconversion yield of ethanol from lignocellulosic feedstocks is negatively affected by the unproductive adsorption of cellulolytic enzymes onto lignin. In this work, soybean protein was used as a lignin-blocking additive, with the aim of improving the production of ethanol from enzymatic hydrolysates of pretreated sugarcane bagasse. Investigation was made of the effects of the type of hydrothermal pretreatment process—steam explosion (SE) or liquid hot water (LHW), loadings of solids and enzymes, and bioreactor type. The addition of soybean protein led to a exceptional 76% increase of glucose released using the LHW pretreated bagasse, after 24 h of reaction, employing a high-solids loading (15%, 〈em〉w〈/em〉/〈em〉v〈/em〉) and a low enzyme dosage (5 FPU/g dry biomass). A significant improvement was also achieved for industrial-like mixing conditions in a bench-scale stirred tank reactor, increasing the glucose released by 61 and 42% for the LHW and SE processes, respectively. Ethanol production was also positively affected by the presence of soybean protein, with increases of up to 86 and 65% for the LHW and SE hydrolysates, compared to the control experiment. Characterization of the sugarcane bagasse after the adsorption of soybean protein, using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), corroborated the higher affinity of the additive for the LHW bagasse. These findings suggest that soybean protein supplementation during enzymatic hydrolysis by commercially available enzymes is an effective strategy for achieving higher saccharification yields from hydrothermally pretreated biomass, hence improving ethanol production.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Corn stalk is not suitable for direct combustion due to poor grindability, high moisture content, and insufficient heating value. The aim of this study was to optimize reaction conditions to improve the quality of corn stalk char, and to investigate the effects of carbonization on the physicochemical and combustion characteristics of corn stalks and chars. Optimal conditions for the carbonization of corn stalk were investigated with regard to temperature, holding time, and particle size. Response surface methodology (RSM) provided satisfactory models of responses, and the optimal conditions for higher heating values were obtained as follows: temperature of 551 °C, holding time of 150 min, and particle size range of 0.8–1.0 mm. In addition, after carbonization, changes in surface morphology, functional groups, and organic elements were clearly observed on the chars. The optimal point char experienced fairly complete carbonization, and holds promise for use as a solid biofuel.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The impacts of hydrothermal and dilute acid pretreatments and alkali and alkaline earth metals (AAEMs) on the thermal degradation of biomass were studied. Besides, the influence of these pretreatments on the biomass ash properties was investigated. The influence of pretreatments on the biomass thermal degradation was manifested in the removal of potassium out of the biomass. The presence of potassium in the biomass catalyzed cellulose thermal degradation and increased the char percentage at temperatures higher than 380 °C. Pretreatments were effective at removing the potassium from biomass and dramatically reduced the char percentage at temperatures higher than 380 °C. It was found that the best burning temperature for biomass ash production was 500 °C because at this temperature the thermal degradation of biomass was completed under pure combustion. It was shown that when burning biomass in oxygen-limited environments, removing AAEMs, particularly potassium, will improve the quality of ash as a potential candidate for supplementary cementitious materials for concrete application.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉To avoid competition with food crops, biofuel feedstocks may need to be produced on economically marginal lands where yields are limited and replacement of existing vegetation will reduce soil C, foregoing some CO〈sub〉2〈/sub〉 emission savings. Therefore, our first goal was to determine whether biochar application to marginal lands could improve switchgrass yield while sequestering sufficient soil C to eliminate the negative impact of cultivation. Because it may be difficult to obtain large quantities of biochar, our second goal was to compare small, incremental and large, all-at-once biochar applications. Our third goal was to determine whether biochar had any negative effects on earthworms, mycorrhizal fungi, soil bacteria, soil fungi, and soil enzyme activity. We grew switchgrass at two sites with poorly drained soils and two sites with excessively drained soils. Irrespective of site, biochar significantly increased yield when we rototilled in the entire amount before planting but not when we applied it incrementally between crop rows using a chisel plow. Biochar increased soil C stocks, in some cases increasing it beyond that found in soils of intact marginal land vegetation. Nevertheless, mixing biochar with soil had little or no impact on earthworm activity, mycorrhizal colonization, soil bacterial and fungal communities, and soil enzyme activities. We conclude that biochar may be part of an effective strategy for producing switchgrass on marginal lands, but the choice of application method depends on the relative importance of several considerations including biochar availability, switchgrass yield, C sequestration, soil erosion, and ease of application.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉〈em〉Kappaphycus alvarezii〈/em〉 is a red macroalgae widely used to produce carrageenan. The carrageenan processing produces a by-product rich in glucan which has been reported as easily hydrolyzed with enzymes, but the hydrolysate forms a gel at usual fermentation temperatures. The purpose of this study was to evaluate the enzymatic hydrolysis integrated with a mild-acid treatment of the by-product to obtain a hydrolysate rich in monomeric sugars. Using an enzyme load of 10 FPU g〈sup〉−1〈/sup〉 of by-product, close to 100 and 14.7% of glucan and galactan conversion were reached, respectively. Increasing the enzyme load to 100 FPU g〈sup〉−1〈/sup〉 raised the galactan conversion to 30%. The mild-acid treatment after enzymatic hydrolysis was satisfactory, increasing the glucose and galactose concentrations, without producing significant amounts of fermentation inhibitors and avoiding the formation of a gel structure. The statistical analysis showed that the main effects on the response were negative for the three independent variables, meaning that the selectivity (〈em〉S〈/em〉) becomes lower when experimental conditions at the higher levels are used (longer time, higher temperature, and acid concentration). Therefore, the integrated enzymatic and acid hydrolysis of the by-product becomes a promising technological route to produce monomeric sugars for bioethanol or fine chemical production.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Insufficient light supply is a major limitation in cultivation of cyanobacteria for scaled-up biofuel production and other biotechnological applications, which has driven interest in nanoparticle-mediated enhancement of cellular light capture. In the present study, 〈em〉Fremyella diplosiphon〈/em〉 wild-type (Fd33) and halotolerant (HSF33-2) strains were grown in solution with 20-, 100-, and 200-nm-diameter gold nanoparticles (AuNPs) to determine their impact on biomass accumulation, pigmentation, and fatty acid methyl ester (FAME) production. Results revealed a significant increase in growth of Fd33 (0.244 ± 0.006) and HSF33-2 (0.112 ± 0.003) when treated with 200-nm AuNPs. In addition, we observed a significant increase in chlorophyll 〈em〉a〈/em〉 accumulation in 200-nm AuNP-treated Fd33 (25.7%) and HSF33-2 (36.3%) indicating that NPs enhanced photosynthetic pigmentation. We did not observe any alteration in FAME composition and biodiesel properties of transesterified 〈em〉F. diplosiphon〈/em〉 lipids among all AuNP treatments. Interactions between 〈em〉F. diplosiphon〈/em〉 and AuNPs were visualized using scanning electron microscopy. Energy dispersive X-ray spectroscopy confirmed the presence of AuNPs outside the cells with aggregation in high cell density locales. Our findings indicate that nanotechnological approaches could significantly enhance growth of the organism with no negative effect on FAME-derived biodiesel properties, thus augmenting 〈em〉F. diplosiphon〈/em〉 potential as a biofuel agent.〈/p〉

Description: Wheat straw is a potential source of feedstock for biofuel production that does not compete with food. We have screened 48 wheat lines from a collection representing a broad range of the biodiversity of wild and domestic wheat. Wheat straw was fractionated into water-soluble and nonsoluble fractions. In the water-soluble fraction (WSF), we found a broad variation in the concentration of free soluble sugars (FSS) and a narrow variation in starch. The FSS fraction could reach levels of reducing sugars as high as 130 g sugar/kg of straw. The analysis of the FSS by ion chromatography indicated that fructose and glucose were the major sugar monomers in this fraction. The composition of the nonsoluble cell wall fraction was determined by both pyrolysis and direct chemical analysis. These analyses showed a limited variation in the lignin or the cellulose fraction. There was a significant degree of variation among wheat lines in the enzymatic saccharification of the straw, following acid pretreatment. Interestingly, the straw from wild wheat had the highest degree of saccharification compared to domestic lines. These findings are of interest for the biofuel industry because they mean that wheat lines can be developed in which a significant amount of free soluble sugars can be easily extracted from straw without the need for costly pretreatment and enzymatic deconstruction. Moreover, the high FSS trait might be combined with the high enzymatic saccharification trait suggesting that wheat lines can be developed with a straw composition better adapted for biofuel production.

Description: Successful establishment of switchgrass ( Panicum virgatum L.) remains a challenge. It is reported that increasing seed-soil contact using a roller could improve switchgrass establishment in silt-loam soils. However, use of rollers is not common among growers and operating them could be difficult. The objective of this study was to assess whether rolling could improve switchgrass stand establishment in sandy-loam soils by increasing seed-soil contact through compacting the soil, and to evaluate the use of cultipacker as a more user-friendly alternative to roller. An experiment was conducted in 2012 and repeated in the 2013 growing season at the University of Massachusetts Agricultural Experiment Station farm in Deerfield. The soil type at the experimental site was Hadley fine sandy loam (nonacid, mesic Typic Udifluvent). The experimental design was a randomized complete block design with four replicates. There were eight treatments including disking-planting (D-P), disking-cultipacking-planting (D-C-P), disking-cultipacking-planting-cultipacking (D-C-P-C), disking-cultipacking-planting-cultipacking-cultipacking (D-C-P-C-C), disking-rolling-planting (D-R-P), disking-rolling-planting-rolling (D-R-P-R), disking-rolling-planting-rolling-rolling (D-R-P-R-R), and disking-rolling-planting-rolling-rolling-rolling (D-R-P-R-R-R). Tiller density was influenced rolling and cultipacking frequency but not by the compaction equipment. Tiller density increased by cultipacking or rolling the soil once (D-C-P-C; D-R-P-R) and two times after planting (D-C-P-C-C; D-R-P-R-R). Disking-planting had the lowest tiller density with 188 and 110 plants (m −2 ) in 2012 and 2013 growing seasons, respectively. Similar to tiller density, biomass yield was not influenced by compaction equipment but by compaction frequency. Higher biomass yield was obtained from soils that were firmed once before and at least once after planting (D-C-P-C; D-R-P-R) compared with seedbed firming only once before planting (D-C-P; D-R-P). In a dry season (2012), a twofold yield increase (1.06 Mg ha −1 ) was obtained from D-C-P-C compared with D-C-P (0.55 Mg ha −1 ). However, two times rolling (D-R-P-R-R-) or cultipacking (D-C-P-C-C) after planting was needed in 2013 to increase the yield compared with D-C-P by 41 %. Our results indicated that using cultipacker as an alternative to roller can be a solution to improve switchgrass establishment. We conclude that D-C-P-C-C could ensure switchgrass establishment and improve switchgrass biomass production in the establishment year in a sandy-loam soil.

Description: Chemical 2,3-butanediol is an important platform compound possessing diverse industrial applications. So far, it is mainly produced by using petrochemical feedstock which is associated with high cost and adverse environmental impacts. Hence, finding alternative routes (e.g., via fermentation using renewable carbon sources) to produce 2,3-butanediol are urgently needed. In this study, we report a wild-type Klebsiella sp. strain XRM21, which is capable of producing 2,3-butanediol from a wide variety of carbon sources including glucose, sucrose, xylose, and glycerol. Among them, fermentation of sucrose leads to the highest production of 2,3-butanediol. To maximize the production of 2,3-butanediol, fermentation conditions were first optimized for strain XMR21 by using response surface methodology (RSM) in batch reactors. Subsequently, a fed-batch fermentation strategy was designed based on the optimized parameters, where 91.2 g/L of 2,3-butanediol could be produced from substrate sucrose dosing in 100 g/L for three times. Moreover, random mutagenesis of stain XMR21 resulted in a highly productive mutant strain, capable of producing 119.4 and 22.5 g/L of 2,3-butanediol and ethanol under optimized fed-batch fermentation process within 65 h with a total productivity of 2.18 g/L/h, which is comparable to the reported highest 2,3-butanediol concentration produced by previous strains. This study provides a potential strategy to produce industrially important 2,3-butanediol from low-cost sucrose.