Transgenic modification of plants is a key enabling technology for developing sustainable biofeedstocks for biofuels production. Regulatory decisions and the wider acceptance and development of transgenic biofeedstock crops are considered from the context of science-based risk assessment. The risk assessment paradigm for transgenic biofeedstock crops is fundamentally no different from that of current generation transgenic crops, except that the focus of the assessment must consider the unique attributes of a given biofeedstock crop and its environmental release. For currently envisioned biofeedstock crops, particular emphasis in risk assessment will be given to characterization of altered metabolic profiles and their implications relative to non-target environmental effects and food safety; weediness and invasiveness when plants are modified for abiotic stress tolerance or are domesticated; and aggregate risk when plants are platforms for multi-product production. Robust risk assessments for transgenic biofeedstock crops are case-specific, initiated through problem formulation, and use tiered approaches for risk characterization.
biomass
The important key technologies required for the successful biological conversion of lignocellulosic biomass to ethanol have been extensively reviewed. The biological process of ethanol fuel production utilizing lignocellulose as substrate requires: (1) delignification to liberate cellulose and hemicellulose from their complex with lignin, (2) depolymerization of the carbohydrate polymers (cellulose and hemicellulose) to produce free sugars, and (3) fermentation of mixed hexose and pentose sugars to produce ethanol. The development of the feasible biological delignification process should be possible if lignin-degrading microorganisms, their ecophysiological requirements, and optimal bioreactor design are effectively coordinated. Some thermophilic anaerobes and recently-developed recombinant bacteria have advantageous features for direct microbial conversion of cellulose to ethanol, i.e. the simultaneous depolymerization of cellulosic carbohydrate polymers with ethanol production. The new fermentation technology converting xylose to ethanol needs also to be developed to make the overall conversion process more cost-effective. The bioconversion process of lignocellulosics to ethanol could be successfully developed and optimized by aggressively applying the related novel science and technologies to solve the known key problems of conversion process.
Production of ethanol from agriculutural and forestry residues, municipal solid waste, energy crops, and other forms of lignocellulosic biomass could improve energy security, reduce trade deficits, decrease urban air pollution, and contribute little, if any, net carbon dioxide accumulation to the atmosphere. Dilute acid can open up the biomass structure for subsequent processing. The simultaneous saccharification and fermentation (SSF) process is favored for producing ethanol from the major fraction of lignocellulosic biomass, cellulose, because of its low cost potential. Technology has also been developed for converting the second largest biomass fraction, hemicellulose, into ethanol. The remaining fraction, containing mostly lignin, can be burned as boiler fuel to power the conversion process and generate extra electricity to export. Developments in conversion technology have reduced the projected gate price of ethanol from about US$0.95/liter (US$3.60/gallon) in 1980 to only about US$0.32/liter (US$1.22/gallon) in 1994. Technical targets have been identified to bring the selling price down to about US$0.18/liter (US$0.67/gallon), a level that is competitive when oil prices exceed US$25/barrel. However, at current projected costs, ethanol from biomass could be competitive with ethanol from corn, particularly if lower cost feedstocks or other niche markets are capitalized upon.
A method is presented, which estimates the potential for power production from agriculture residues. A GIS decision support system (DSS) has been developed, which implements the method and provides the tools to identify the geographic distribution of the economically exploited biomass potential. The procedure introduces a four level analysis to determine the
theoretical, available, technological and economically exploitable potential. The DSS handles all possible restrictions and
candidate power plants are identi ed using an iterative procedure that locates bioenergy units and establishes the needed cultivated area for biomass collection. Electricity production cost is used as a criterion in the identi cation of the sites of economically exploited biomass potential. The island of Crete is used as an example of the decision-making analysis. A signi cant biomass potential exists that could be economically and competitively harvested. The main parameters that affect the location and number of bioenergy conversion facilities are plant capacity and spatial distribution of the available biomass potential.
United States is experiencing increasing interests in fermentation and anaerobic digestion processes for the production of biofuels. A simple methodology of spatial biomass assessment is presented in this paper to evaluate biofuel production and support the first decisions about the conversion technology applications. The methodology was applied to evaluate the potential biogas and ethanol production from biomass in California and Washington states. Solid waste databases were filtered to a short list of digestible and fermentable wastes in both states. Maximum methane and ethanol production rates were estimated from biochemical and ultimate analysis of each waste and projected on a GIS database. Accordingly, the optimal locations for methane and ethanol production plants were approximately determined.
The available net power for transportation and electricity generation was evaluated considering three process efficiency factors in the waste to power life cycle. The net power from methane and ethanol would ultimately cover ~ 6 - 8% of the transportation needs for motor gasoline or cover ~ 3 - 4% of the electrical power consumption in each state.
There is a strong societal need to evaluate and understand the sustainability of biofuels, especially because of the significant increases in production mandated by many countries, including the United States. Sustainability will be a strong factor in the regulatory environment and investments in biofuels. Biomass feedstock production is an important contributor to environmental, social, and economic impacts from biofuels. This study presents a systems approach where the agricultural, energy, and environmental sectors are considered as components of a single system, and environmental liabilities are used as recoverable resources for biomass feedstock production. We focus on efficient use of land and water resources. We conducted a spatial analysis evaluating marginal land and degraded water resources to improve feedstock productivity with concomitant environmental restoration for the state of Nebraska. Results indicate that utilizing marginal land resources such as riparian and roadway buffer strips, brownfield sites, and marginal agricultural land could produce enough feedstocks to meet a maximum of 22% of the energy requirements of the state compared to the current supply of 2%. Degraded water resources such as nitrate-contaminated groundwater and wastewater were evaluated as sources of nutrients and water to improve feedstock productivity. Spatial overlap between degraded water and marginal land resources was found to be as high as 96% and could maintain sustainable feedstock production on marginal lands. Other benefits of implementing this strategy include feedstock intensification to decrease biomass transportation costs, restoration of contaminated water resources, and mitigation of greenhouse gas emissions.
Biomass is receiving increasing attention as scientists, policy makers, and growers search for clean, renewable energy alternatives. Compared with other renewable resources, biomass is very flexible it can be used as fuel for direct combustion, gasified, used in combined heat and power technologies, or biochemical conversions. Due to the wide range of feedstocks, biomass has a broad geographic distribution, in some cases offering a least-cost and near-term alternative. The objective of this research is to estimate the biomass resources available in the United States and map the results. To accomplish this objective, biomass feedstock data are analyzed both statistically and graphically using geographic information systems (GIS). A GIS is a computer-based information system used to create, manipulate, and analyze geographic information, allowing us to visualize relationships, patterns, or trends that are not possible to see with traditional charts, graphs, and spreadsheets. While other biomass resource assessments concentrate on the economic or theoretical availability, this study estimates the technical biomass resources available in the United States (page 59). The estimates are based on numerous assumptions, methodologies adopted from other studies, and factors that relate population to the amount of post-consumer residue generation. The main contribution of this research is that it adds a geographic perspective to biomass research by answering questions such as where the resources are and how much is available.
"Sustainable development," according to the United Nations' World Commission on Environment and Development, "meets the needs of the present without compromising the needs of the future generations." It is hard to argue with the idea of sustainability when it is couched in these terms. Beyond this broad and highly idealized view of sustainable development lies a more problematic definition-one that recognizes sustainable development as a careful balancing act among issues of environmental protection, public health and safety, and sound economic development.
Biomass is a significant contributor to the US economy--agriculture, forest and paper products, food and related products account for 5% of our GDP. While the forest products industry self generates some of their energy, other sectors are importers. Bioenergy can contribute to economic development and to the environment. Examples of bioenergy routes suggest that atmospheric carbon can be cycled through biofuels in carefully designed systems for sustainability. Significant potential exists for these options. Research and development of integrated biomass reduction and conversion systems, as currently being performed in the Biomass for Rural Development Program, can help verify the potential energy, economic, and environmental benefits and advance biomass and bioenergy into the 21st century.
Electric power production from biomass has the potential to make significant contributions to the power mix in the U.S., and to do so with substantially fewer environmental impacts than current technologies. Using dedicated energy crops for power production will significantly close the carbon cycle, reduce and stabilize feedstock costs, increase the feasible size of biomass power plants, and provide economic benefits to agricultural communities.