Environmental Consequences of Ethanol from Corn Grain, Ethanol from Lignocellulosic Biomass, and Conventional Gasoline (original) (raw)
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Economic and environmental impacts of U.S. corn ethanol production and use
2009
aware of the enhanced demand represented by entry into world markets of new players, including other Eastern European countries and China. More recent history has been characterized by U.S. government policies that encouraged the production of biofuels (for several reasons) and high prices for commodities, including crude oil. This article reviews the history of and motivations for the policies encouraging corn ethanol production and how the original intent of these policies became magnified in a time of rapidly rising energy prices. Throughout the following discussion, it is important to distinguish the effects of corn ethanol production from the amplified effects of corn ethanol production resulting from crude oil price changes. These changes were driven by a rapidly growing demand for energy in emerging economies during wars or potential conflicts that have involved key petroleum-producing regions.
Replacing Gasoline with Corn Ethanol Results in Significant Environmental Problem-Shifting
Environmental Science & Technology, 2012
Previous studies on the life-cycle environmental impacts of corn ethanol and gasoline focused almost exclusively on energy balance and greenhouse gas (GHG) emissions and largely overlooked the influence of regional differences in agricultural practices. This study compares the environmental impact of gasoline and E85 taking into consideration 12 different environmental impacts and regional differences among 19 corngrowing states. Results show that E85 does not outperform gasoline when a wide spectrum of impacts is considered. If the impacts are aggregated using weights developed by the National Institute of Standards and Technology (NIST), overall, E85 generates approximately 6% to 108% (23% on average) greater impact compared with gasoline, depending on where corn is produced, primarily because corn production induces significant eutrophication impacts and requires intensive irrigation. If GHG emissions from the indirect land use changes are considered, the differences increase to between 16% and 118% (33% on average). Our study indicates that replacing gasoline with corn ethanol may only result in shifting the net environmental impacts primarily toward increased eutrophication and greater water scarcity. These results suggest that the environmental criteria used in the Energy Independence and Security Act (EISA) be re-evaluated to include additional categories of environmental impact beyond GHG emissions.
Reducing Life-Cycle Greenhouse Gas Emissions of Corn Ethanol
2010
A life-cycle assessment (LCA) of corn ethanol was conducted to determine the reduction in the life-cycle greenhouse gas (GHG) emissions for corn ethanol compared to gasoline by integrating biomass fuels to replace fossil fuels (natural gas and grid electricity) in a U.S. Midwest dry-grind corn ethanol plant producing 0.19 hm 3 y À1 of denatured ethanol. The biomass fuels studied are corn stover and ethanol co-products [dried distillers grains with solubles (DDGS), and syrup (solubles portion of DDGS)]. The biomass conversion technologies/systems considered are process heat (PH) only systems, combined heat and power (CHP) systems, and biomass integrated gasification combined cycle (BIGCC) systems. The life-cycle GHG emission reduction for corn ethanol compared to gasoline is 38.9% for PH with natural gas, 57.7% for PH with corn stover, 79.1% for CHP with corn stover, 78.2% for IGCC with natural gas, 119.0% for BIGCC with corn stover, and 111.4% for BIGCC with syrup and stover. These GHG emission estimates do not include indirect land use change effects. GHG emission reductions for CHP, IGCC, and BIGCC include power sent to the grid which replaces electricity from coal. BIGCC results in greater reductions in GHG emissions than IGCC with natural gas because biomass is substituted for fossil fuels. In addition, underground sequestration of CO 2 gas from the ethanol plant's fermentation tank could further reduce the life-cycle GHG emission for corn ethanol by 32% compared to gasoline.
Ethanol production: energy, economic, and environmental losses
Reviews of environmental contamination and toxicology, 2007
The prime focus of ethanol production from corn is to replace the imported oil used in American vehicles, without expending more fossil energy in ethanol production than is produced as ethanol energy. In a thorough and up-to-date evaluation of all the fossil energy costs of ethanol production from corn, every step in the production and conversion process must be included. In this study, 14 energy inputs in average U.S. corn production are included. Then, in the fermentation/distillation operation, 9 more identified fossil fuel inputs are included. Some energy and economic credits are given for the by-products, including dried distillers grains (DDG). Based on all the fossil energy inputs, a total of 1.43 kcal fossil energy is expended to produced 1 kcal ethanol. When the energy value of the DDG, based on the feed value of the DDG as compared to that of soybean meal, is considered, the energy cost of ethanol production is reduced slightly, to 1.28 kcal fossil energy input per 1 kcal ...
Journal of the Air & Waste Management Association, 2010
This paper reports on the estimated potential air emissions, as found in air permits and supporting documentation, for seven of the first group of precommercial or "demonstration" cellulosic ethanol refineries (7CEDF) currently operating or planning to operate in the United States in the near future. These seven refineries are designed to produce from 330,000 to 100 million gal of ethanol per year. The overall average estimated air emission rates for criteria, hazardous, and greenhouse gas pollutants at the 7CEDF are shown here in terms of tons per year and pounds per gallon of ethanol produced. Water use rates estimated for the cellulosic ethanol refineries are also noted. The air emissions are then compared with similar estimates from a U.S. cellulosic ethanol pilot plant, a commercial Canadian cellulosic ethanol refinery, four commercial U.S. corn ethanol refineries, and U.S. petroleum refineries producing gasoline. The U.S. Environmental Protection Agency (EPA) air pollution rules that may apply to cellulosic ethanol refineries are also discussed. Using the lowest estimated emission rates from these cellulosic ethanol demonstration facilities to project air emissions, EPA's major source thresholds for criteria and hazardous air pollutants might not be exceeded by cellulosic ethanol refineries that produce as high as 25 million gal per year of ethanol (95 ML). Emissions are expected to decrease at cellulosic ethanol refineries as the process matures and becomes more commercially viable. IMPLICATIONS Development of the next generation of biofuels is already underway with the recent development and operation of approximately 25 cellulosic ethanol demonstration refineries in the United States. These fledgling biofuel refineries, many funded in part by the U.S. Department of Energy, are attempting to show that the production of fuel from nonfood but carbon-neutral sources is economically and technically feasible. The environmental impacts in terms of air and water are being closely watched; this paper shows that low impacts appear to be achievable.
From the Cover: Environmental, economic, and energetic costs and benefits of biodiesel and ethanol b
Pnas, 2006
Negative environmental consequences of fossil fuels and concerns about petroleum supplies have spurred the search for renewable transportation biofuels. To be a viable alternative, a biofuel should provide a net energy gain, have environmental benefits, be economically competitive, and be producible in large quantities without reducing food supplies. We use these criteria to evaluate, through life-cycle accounting, ethanol from corn grain and biodiesel from soybeans. Ethanol yields 25% more energy than the energy invested in its production, whereas biodiesel yields 93% more. Compared with ethanol, biodiesel releases just 1.0%, 8.3%, and 13% of the agricultural nitrogen, phosphorus, and pesticide pollutants, respectively, per net energy gain. Relative to the fossil fuels they displace, greenhouse gas emissions are reduced 12% by the production and combustion of ethanol and 41% by biodiesel. Biodiesel also releases less air pollutants per net energy gain than ethanol. These advantages of biodiesel over ethanol come from lower agricultural inputs and more efficient conversion of feedstocks to fuel. Neither biofuel can replace much petroleum without impacting food supplies. Even dedicating all U.S. corn and soybean production to biofuels would meet only 12% of gasoline demand and 6% of diesel demand. Until recent increases in petroleum prices, high production costs made biofuels unprofitable without subsidies. Biodiesel provides sufficient environmental advantages to merit subsidy. Transportation biofuels such as synfuel hydrocarbons or cellulosic ethanol, if produced from low-input biomass grown on agriculturally marginal land or from waste biomass, could provide much greater supplies and environmental benefits than food-based biofuels. corn | soybean | life-cycle accounting | agriculture | fossil fuel