ALBERT

Description: ▪ Abstract  Ethanol made from lignocellulosic biomass sources, such as agricultural and forestry residues and herbaceous and woody crops, provides unique environmental, economic, and strategic benefits. Through sustained research funding, primarily by the U.S. Department of Energy, the estimated cost of biomass ethanol production has dropped from ∼$4.63/gallon in 1980 to ∼$1.22/gallon today, and it is now potentially competitive for blending with gasoline. Advances in pretreatment by acid-catalyzed hemicellulose hydrolysis and enzymes for cellulose breakdown coupled with recent development of genetically engineered bacteria that ferment all five sugars in biomass to ethanol at high yields have been the key to reducing costs. However, through continued advances in accessing the cellulose and hemicellulose fractions, the cost of biomass ethanol can be reduced to the point at which it is competitive as a pure fuel without subsidies. A major challenge to realizing the great benefits of biomass ethanol remains to substantially reduce the risk of commercializing first-of-a-kind technology, and greater emphasis on developing a fundamental understanding of the technology for biomass conversion to ethanol would reduce application costs and accelerate commercialization. Teaming of experts to cooperatively research key processing steps would be a particularly powerful and effective approach to meeting these needs.

Description: ▪ Abstract  Six methods for attributing ambient pollutants to emission sources are reviewed: emissions analysis, trend analysis, tracer studies, trajectory analysis, receptor modeling, and dispersion modeling. The ranges of applicability, types of information provided, limitations, performance capabilities, and areas of active research of the different methods are compared. For primary, nonreactive pollutants whose effects of concern occur on a global scale, an accounting of emissions rates by source type and location largely characterizes source contributions. For other pollutants or smaller spatial scales, accurate estimates of emissions are needed for identifying the emissions reduction potentials of possible control measures and as inputs to dispersion models. Emission levels are frequently known with factor-of-two accuracy or worse, and improved estimates are needed for dispersion modeling. The analysis of regional or urban-scale trends in emissions and ambient pollutant concentrations can provide qualitative information on source contributions, but quantitative results are limited by the confounding influence of variations in meteorology and uncertainties in the areas over which emissions affect concentrations. Tracer studies are useful for quantifying dispersion characteristics of plumes, qualitatively characterizing transport directions, and providing empirical data for evaluating trajectory and dispersion models. Data are usually temporally limited to a short study period, typically do not provide information on vertical pollutant distributions, and are most applicable to the transport of primary, nonreactive pollutants. Trajectory analyses are routinely used to estimate atmospheric transport directions. Trajectory errors of about 20% of travel distance are considered typical of the better models and data sets. Receptor models use measurements of ambient pollutant concentrations to quantify the contributions of different source types to primary particulate matter or volatile organic compounds, or to characterize source-region contributions to a single pollutant. Accuracy rates of ∼30% are often achieved when quantifying the contributions from different types of emission sources. Dispersion models are well-suited for estimating quantitative source-receptor relationships, as the effects of individual emission sources or source regions can be studied. Lagrangian and Gaussian dispersion models are computationally efficient and can simulate the transport of nonreactive primary or linear secondary species. Eulerian models are computationally intensive but lend themselves to the simulation of nonlinear chemistry. Careful evaluation of modeling accuracy is needed for a model application to fulfill its potential for source attribution. Accuracy can be evaluated through a combination of performance evaluation, sensitivity analysis, diagnostic evaluation, and corroborating analyses.

Description: ▪ Abstract  This paper reviews the empirical evidence for the following five hypotheses from the economic growth-liberalization-pollution debate: (a) economic growth will lead to a worsening pollution problem; (b) tighter environmental regulation will reduce economic growth; (c) trade liberalization will exacerbate environmental degradation, especially in developing countries with weak environmental protection; (d) tighter environmental protection in the developed countries will lead to a loss of competitiveness compared with that of countries with lower standards, especially in polluting industries; and (e) tighter environmental protection in the developed countries will lead to relocation of investment to developing countries with lax regulation, especially in polluting industries (the pollution haven hypothesis). Overall, the evidence for these hypotheses is found to be ambiguous and weak. It is further suggested that the growth-liberalization-environment empirical literature has neglected three important elements: (a) environmental innovation, (b) the international diffusion of environmental technologies, and (c) the economic benefits of a cleaner environment. Future research should integrate these elements into the debate. Analyses of endogenous environmental innovation in response to environmental policy, the tradable nature of environmental technologies, the role of trade and foreign direct investment as channels of environmental-technology transfer to developing countries, the effects of local environmental policies in encouraging the adoption of such technologies in developing countries, and the economic benefits of a cleaner environment would contribute to the development of sound, well-coordinated economic and environmental policies.

Description: ▪ Abstract  Although global warming is generally linked to increasing levels of carbon dioxide, there are many other gases produced from industrial, agricultural, and energy-generating sources that can also cause the Earth's temperature to rise. Individually these gases are not likely to make a significant contribution, but, taken together, it is believed that they can rival the effects of carbon dioxide. This paper reviews the current trends of the most abundant or the most effective of these non-CO2 greenhouse gases. Methane, nitrous oxide, and the major chlorofluorocarbons (F-11 and F-12) have been the most notable greenhouse gases other than CO2. Although these gases will continue to play a role in global warming, new compounds are likely to become increasingly important. These include the fluorocarbon replacement compounds in the hydrofluorocarbon and the hydrochlorofluorocarbon groups and gases that are nearly inert in the atmosphere, persisting for thousands of years, such as the perfluorocarbons and sulfur hexafluoride.

Description: ▪ Abstract  Of the thousands of species of microalgae that form the base of the marine food chain, only a small number are toxic or harmful. However, when these toxic species proliferate, they can cause massive kills of fish and shellfish, mortality among marine mammals and seabirds, substantive alterations of marine habitats, and human illness and death. Currently, six distinct human clinical syndromes associated with harmful algal blooms are recognized: ciguatera fish poisoning, paralytic shellfish poisoning, neurotoxic shellfish poisoning, diarrhetic shellfish poisoning, amnesic shellfish poisoning, and Pfiesteria-associated syndrome. Human illnesses are caused by toxins produced by these microorganisms, acquired either by passage through the food chain or direct skin or respiratory contact. Syndromes frequently include debilitating neurologic manifestations and, in some instances, may progress to death. There is a perception among investigators that the number of harmful algal blooms is increasing, as is the range of toxic species. It has been postulated that this increase is caused by human-related phenomena such as disruption of ecosystems, nutrient enrichment of waterways, and climatic change. In environmental studies, attention has traditionally focused on direct human health effects of pollutants. Harmful algal blooms are an example of an alternative paradigm, in which human-induced stress on complex ecologic systems leads to the emergence of new, potentially harmful microorganisms (or the reemergence of “old” pathogens from previously restricted environmental niches), which, in turn, cause human disease. Although data are lacking to fully substantiate this latter model, it provides a useful conceptual framework to assess data needs and consider public health interventions.

Description: ▪ Abstract  Yucca Mountain, NV, is being characterized for disposal of U.S. high-level nuclear waste, which consists predominantly of spent fuel from nuclear reactors and radioactive waste from reprocessing. In this paper, the program is presented in the context of global and U.S. nuclear energy systems and of international plans for high-level waste disposal. The potential impact of the proposed repository is discussed in the context of the U.S. Department of Energy's Total System Performance Assessment-Viability Assessment, the primary tool for assessing how the repository might operate.

Description: ▪ Abstract  The US-Mexico border region illustrates the challenges of binational environmental management in the context of a harsh physical environment, rapid growth, and economic integration. Transboundary and shared resources and conflicts include limited surface water supplies, depletion of groundwater, air and water pollution, hazardous waste, and conservation of important natural ecosystems. Public policy responses to environmental problems on the border include binational institutions such as the IBWC, BECC and CEC, the latter two established in response to environmental concerns about the North American Free Trade Agreement (NAFTA). Environmental social movements and nongovernmental organizations have also become important agents in the region. These new institutions and social movements are especially interesting on the Mexican side of the border where political and economic conditions have often limited environmental enforcement and conservation, and where recent policy changes also include changes in land and water law, political democratization, and government decentralization.

Description: ▪ Abstract  About two-thirds of primary energy today is used directly as transportation and heating fuels. Any discussion of energy-related issues, such as air pollution, global climate change, and energy supply security, raises the issue of future use of alternative fuels. Hydrogen offers large potential benefits in terms of reduced emissions of pollutants and greenhouse gases and diversified primary energy supply. Like electricity, hydrogen is a premium-quality energy carrier, which can be used with high efficiency and zero emissions. Hydrogen can be made from a variety of feedstocks, including natural gas, coal, biomass, wastes, solar sources, wind, or nuclear sources. Hydrogen vehicles, heating, and power systems have been technically demonstrated. Key hydrogen end-use technologies such as fuel cells are making rapid progress toward commercialization. If hydrogen were made from renewable or decarbonized fossil sources, it would be possible to have a large-scale energy system with essentially no emissions of pollutants or greenhouse gases. Despite these potential benefits, the development of a large-scale hydrogen energy infrastructure is often seen as an insurmountable technical and economic barrier. Here we review the current status of technologies for hydrogen production, storage, transmission, and distribution; describe likely areas for technological progress; and discuss the implications for developing hydrogen as an energy carrier.

Description: This review presents a personal view of the development of plant physiological ecology, the science of studying biological diversity, and the functioning of the Earth as a system. The need for interaction among these disciplines is becoming increasingly urgent as we are faced with the challenge of “managing” the Earth system that is increasingly impacted by the activities of humans.

Description: ▪ Abstract  Technology largely determines economic development and its impact on the environment; yet technological change is one of the least developed parts of existing global change models. This paper reviews two approaches developed at the International Institute for Applied Systems Analysis, both of which use the concept of technological learning and aid modeling of technological change. The first approach is a micromodel (“bottom-up”) of three electricity generation technologies that rigorously endogenizes technological change by incorporating both uncertainty (stochasticity) and learning into the model's decision rules. This model, with its endogenous technological change, allows radical innovations to penetrate the energy market and generates S-shaped patterns of technological diffusion that are observed in the real world. The second approach is a macro (“top-down”) model that consists of coupled economic- and technological-system models. Although more stylistic in its representation of endogenous technological change, the macro model can be applied on a worldwide scale and can generate long-term scenarios that are critical for policy analysis. Both the micro- and macro models generate radical departures from currently dominant technological systems (“surprises”), including long-term scenarios with low carbon and sulfur emissions. Our focus is modeling, but for policy, the work underscores the need for huge investments before environmentally superior technologies can compete in the market.