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.  FIND ARTICLE HERE

In this paper, we assess what is known or anticipated about environmental and sustainability factors associated with next-generation biofuels relative to the primary conventional biofuels (i.e., corn grain-based ethanol and soybean-based diesel) in the United States during feedstock production and conversion processes. Factors considered include greenhouse (GHG) emissions, air pollutant emissions, soil health and quality, water use and water quality, wastewater and solid waste streams, and biodiversity and land-use changes. Based on our review of the available literature, we find that the production of next-generation feedstocks in the U.S. (e.g., municipal solid waste, forest residues, dedicated energy crops, microalgae) are expected to fare better than corn-grain or soybean production on most of these factors, although the magnitude of these differences may vary significantly among feedstocks. Ethanol produced using a biochemical or thermochemical conversion platform is expected to result in fewer GHG and air pollutant emissions, but to have similar or potentially greater water demands and solid waste streams than conventional ethanol biorefineries in the U.S. However, these conversion-related differences are likely to be small, particularly relative to those associated with feedstock production.

Modeling performed for illustrative purposes and to allow for standardized quantitative comparisons across feedstocks and conversion technologies generally confirms the findings from the literature. Despite current expectations, significant uncertainty remains regarding how well next-generation biofuels will fare on different environmental and sustainability factors when produced on a commercial scale in the U.S. Additional research is needed in several broad areas including quantifying impacts, designing standardized metrics and approaches, and developing decision-support tools to identify and quantify environmental trade-offs and ensure sustainable biofuels production.  FIND ARTICLE HERE

Recent analysis of the energy and greenhouse-gas performance of alternative biofuels have ignited a controversy that may be best resolved by applying two simple principles. In a world seeking solutions to its energy, environmental, and food challenges, society cannot afford to miss out on the global greenhouse-gas emission reductions and the local environmental and societal benefits when biofuels are done right. However, society also cannot accept the undesirable impacts of biofuels done wrong.  FIND ARTICLE HERE

Ensuring inexpensive and clean water is an overriding global challenge noted as one of the Millennium Development Goals of the United Nations. This challenge will likely be intensified by the increasing demand for biomass-derived fuels (i.e., biofuels) for transportation biofuel needs, because (1) large quantities of water are needed to grow the fuel crops, and (2) water pollution is exacerbated by agricultural drainage containing fertilizers, pesticides, and sediment. These potential drawbacks are balanced by biofuels’ significant potential to ease dependence on foreign oil and improve trade balance(s) while mitigating air pollution and reducing fossil carbon emissions to the atmosphere.

The water requirements of biofuel production depend on the type of feedstock used and on geographic and climatic variables. Such factors must be considered to determine water requirements and identify critical scenarios and mitigation strategies. Feedstock cultivation, usually row-crop agriculture, is the most water-intensive of biofuel production stages. For example, evapotranspiration water requirements in the U.S. necessitate 500-4000 L of water to grow enough feedstock to produce1Lof ethanol (Lw/Le) (Figure 1); processing water requirements for a typical sugar cane or corn ethanol refinery are only 2-10 Lw/Le (17). Nevertheless, the water used in biofuel processing and other stages in biofuel production is often withdrawn from local point sources and can have localized impacts on water quality and quantity.
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Prior studies have estimated that a liter of bioethanol requires 263-784 L of water from corn farm to fuel pump, but these estimates have failed to account for the widely varied regional irrigation practices. By using regional time-series agricultural and ethanol production data in the U.S., this paper estimates the state-level field-to-pump water requirement of bioethanol across the nation. The results indicate that bioethanol’s water requirements can range from 5 to 2138 L per liter of ethanol depending on regional irrigation practices. The results also show that as the ethanol industry expands to areas that apply more irrigated water than others,consumptive water appropriation by bioethanol in the U.S. has increased 246% from 1.9 to 6.1 trillion liters between 2005 and 2008, whereas U.S. bioethanol production has increased only 133% from 15 to 34 billion liters during the same period. The results highlight the need to take regional specifics into account when implementing biofuel mandates.  FIND ARTICLE HERE

In this paper, we review some of the basic energy balance and climate change impact issues associated with biofuels. For both the basic energy and greenhouse gas balances of producing and using a range of fuels, and for the increasingly debated and important issues of non-greenhouse gas impacts such as land, fertilizer, and water use, we conclude that an improved framework for the analysis and evaluation of biofuels is needed. These new methodologies and data sets are needed on both physical and socioeconomic aspects of the life-cycle of biofuels.

We detail some of components that could be used to build this methodology and highlight key areas for future research. We look at the history and potential impacts of building the resource base for biofuel research, as well as at some of the land-use and socioeconomic impacts of different feedstock-to-fuel pathways.
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The quantity of land available to grow biofuel crops without affecting food prices or greenhouse gas (GHG) emissions from land conversion is limited. Therefore, bioenergy should maximize land-use efficiency when addressing transportation and climate change goals. Biomass could power either internal combustion or electric vehicles, but the relative land-use efficiency of these two energy pathways is not well quantified. Here, we show that bioelectricity outperforms ethanol across a range of feedstocks,conversion technologies, and vehicle classes. Bioelectricity produces an average of 81% more transportation kilometers and 108% more emissions offsets per unit area of cropland than does cellulosic ethanol. These results suggest that alternative bioenergy pathways have large differences in how efficiently they use the available land to achieve transportation and climate goals.  FIND ARTICLE HERE

The purpose of this study is to consolidate and document the progress to date and development status of biomass-to-alcohol (bioalcohol) production technologies, and to help guide continued development activities in the Western region and elsewhere. Specific objectives outlined for the study are to:

(1) Review and evaluate candidate technologies for producing ethanol and other alcohols from cellulosic biomass feedstocks, describing development progress to date and future prospects for these technologies.

(2) Review and summarize relevant past bioalcohol production technology projects studied or proposed in the Western United States (namely California).

(3) Identify opportunities for new projects involving applications of candidate bioalcohol production technologies using come of the West's cellulosic biomass resources.

(4) Identify remaining regulatory, economic and institutional obstacles to bioalcohol project development and describe state and federal government roles in addressing these challenges.
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Biofuels derived from renewable resources are thought to help reduce greenhouse gas emissions.  However, a Swiss study by Zah et al. (German) looks at the full life-cycle costs of 26 different biofuels produced from a wide variety of crops.  The study assesses the total environmental impact of each biofuel by aggregating natural resource depletion and damage to human health and ecosystems into a single indicator.  A second criterion for each fuel is its greenhouse-gas emissions relative to gasoline.

The majority (21 of 26) of the biofuels reduce greenhouse-gas emissions by more than 30% relative to gasoline.  However, nearly half (12 of 26) of the biofuels, including the most widely spread (U.S corn ethanol, Brazilian sugarcane ethanol and soy diesel, and Malaysian palm-oil diesel) have larger aggregate environmental costs than do fossil fuels.

The Biofuels that fair best are those produced from residual products (biowaste, recycled cooking oil, and ethanol from grass and wood).

This article outlines some of the imperfections in the Zah et al. analysis, namely: collapsing all environmental costs into a single number, failing to quantify all of the indirect effects of biofuels (subsidies that shift U.S. soy fields to corn, thereby increasing the cost of soy on the global market, and incentivizing the destruction of tropical savannas for soy production), the over reliance on old data sets (2004), the social consequences of large-scale biofuels production on global food prices, and the inclusion of many second-generation biofuels that can be produced from nonfood plants (prairie grasses, trees grown on marginal land, and algaculture).
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The overall chemical stoichiometry in the conversion of corn stover, switch grass, wood, corn stover lignin, C6 sugar, C6 polysaccharide, C5 sugar, and C5 polysaccharide to ethanol, butanol, hexane, and benzene is explained. The theoretical amount of fuel that can be made from these biomass sources and how much water is required for each reaction is determined. The maximum fuel volume yield for ethanol is 382.7 gallons per ton of corn stover lignin. However this process requires 163.9 gallons of water per ton of feedstock.
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The ammonia fiber expansion (AFEX) process has been shown to be an effective pretreatment for lignocellulosic biomass. Technological advances in AFEX have been made since previous cost estimates were developed for this process. Recent research has enabled lower overall ammonia requirements, reduced ammonia concentrations, and reduced enzyme loadings while still maintaining high conversions of glucan and xylan to monomeric sugars. A new ammonia recovery approach has also been developed. Capital and operating costs for the AFEX process, as part of an overall biorefining system producing fuel ethanol from biomass have been developed based on these new research results. These new cost estimates are presented and compared to previous estimates. Two biological processing options within the overall biorefinery are also compared, namely consolidated bioprocessing (CBP) and enzymatic hydrolysis followed by fermentation. Using updated parameters and ammonia recovery configurations, the cost of ethanol production utilizing AFEX is calculated. These calculations indicate that the minimum ethanol selling price (MESP) has been reduced from $1.41/gal to $0.81/gal.  FIND ARTICLE HERE

This study describes how some biofuels are produced, emphasizing agricultural production systems, and considers what is needed in order to measure and communicate environmental performance, and gives examples of how this might be done. We describe a set of seven uses of a Green Biofuels Index, from a wholly market-driven implementation through a set of increasingly intrusive regulatory approaches. We then present several case studies of specific biofuel production pathways using a lifecycle analysis of the inputs to feedstock production and processing, but excluding market-mediated effects.

We recommend four steps to create markets for green biofuels: 1. Measure the global warming intensity of biofuels. 2. Measure the overall environmental performance of biomass feedstock production. 3. Develop and implement a combined Green Biofuels Index. 4. Research better practices, assessment tools, and assurance methods.  FIND ARTICLE HERE

In this paper, we review some of the basic energy balance and climate change impact issues associated with biofuels. For both the basic energy and greenhouse gas balances of producing and using a range of fuels, and for the increasingly debated and important issues of non-greenhouse gas impacts such as land, fertilizer, and water use, we conclude that an improved framework for the analysis and evaluation of biofuels is needed. These new methodologies and data sets are needed on both physical and socioeconomic aspects of the life-cycle of biofuels.  We detail some of components that could be used to build this methodology and highlight key areas for future research. We look at the history and potential impacts of building the resource base for biofuel research, as well as at some of the land-use and socioeconomic impacts of different feedstock-to-fuel pathways.  FIND ARTICLE HERE