"Air Quality and GHG Emissions Associated with Using Ethanol in Gasoline Blends" by David Andress & Associates, Inc. May, 2000 http://www.ott.doe.gov/biofuels/newsearchdb2.cgi?4645 32 pg. PDF
[ Some excerpts ] ABSTRACT This paper presents an overview of the issues related to air quality and greenhouse gas (GHG) emissions associated with ethanol used in gasoline blends. The air quality issues, in particular, are the subject of current regulatory interest because of the potential widespread replacement of MTBE with ethanol. The detection of MTBE in groundwater is growing, and a national debate about its continued use gasoline is currently taking place. The intent of this paper is to provide a short set of standalone topics that will provide a quick reference source for both federal and state government officials and the interested public. The reader is assumed to have some familiarity with the issues involved. The principal air quality concerns arising from gasoline-powered mobile-source emissions are ozone, toxic air pollutants, and carbon monoxide. The major ozone precursors come from emissions of volatile organic compounds (VOC) and nitrous oxides (NOx), and to a lesser extent carbon monoxide (CO). Because ozone formation is related to temperature and solar intensity, ozone problems occur primarily in hot weather. Toxic air pollutants are a year-round problem, but are more pronounced in hot weather. Carbon monoxide emissions from mobile sources are greater in cold weather, and unhealthy levels of CO are primarily a wintertime air quality problem. The problem of determining how emissions affect global warming differs from the problem of determining how emissions affect urban pollution in several important ways. First, the major GHG emissions are CO2, CH4, and N20, are not regulated by EPA as contributors to urban air quality problems. Second, climate change is a global problem and must consider emissions from the total fuel cycle (feedstock production fuel conversion, and vehicle combustion). Urban pollution is a localized problem and EPA regulates only emissions associated with vehicle use. Biomass fuels from ethanol emit no net carbon emissions from fuel combustion, since the carbon in the fuel is withdrawn from the environment during feedstock growth. Corn ethanol used in E10 is currently estimated to reduce GHG emissions between 12 and 19 percent relative to gasoline, depending on whether wet or dry milling is used. GHG emission reductions for future corn ethanol are projected to be between 24 and 26 percent. The increase in GHG emission reductions is due to advances in farming practices and ethanol conversion technologies. For future cellulosic ethanol used in E10, reductions in GHG emissions are projected to be between 84 and 130 percent, depending on whether herbaceous or woody biomass is used. GHG reductions greater than 100% are explained by a coproduct credit for the sale of electricity from cellulosic ethanol plants. Background Ethanol was first used as a motor vehicle fuel in 1908, but remained a small niche fuel favored by racers for many years. Beginning in the 1970s, several events occurred that led to the introduction of ethanol into the commercial gasoline market. - Energy security concerns brought about by the Arab oil embargo spurred Congress to enact tax incentives to encourage the production of alternative fuels. - Around the same time, concerns about environmental impacts associated with gasoline began to emerge. The banning of lead in gasoline created a demand for blending agents, like ethanol, with a high octane content. - Ethanol demand further increased after Congress passed legislation requiring the use of oxygenates in gasoline to reduce harmful emissions from mobile sources. - Global warming, considered the next major environmental front by many people, may further boost the demand for ethanol. Ethanol, being a renewable fuel, produces less GHG emissions than gasoline. - As part of a broad program to improve the nation's air quality, the Clean Air Act Amendments of 1990 (CAAA) impose requirements on fuels sold in urban areas with air quality problems. The CAAA requires the use of reformulated gasoline (RFG) in ozone nonattainment areas and oxygenated fuels in winter carbon monoxide nonattainment areas. - The RFG program is designed to reduce mobile-source emissions that produce ozone and toxic air pollutants. The CAAA requires all RFG to contain an average of at least of 2.0 wt% oxygen and winter oxygenated fuels to contain an average of at least of 2.7 wt% oxygen. Most oxygen requirements are currently satisfied by either ethanol or methyl tertiary butyl ether (MTBE). This paper focuses primarily on issues related to air quality and GHG emissions associated with ethanol used in blends (E10, E7.7, and E5.7). More than 99 percent of the ethanol currently consumed in the U.S. is in the gasoline blend market. Air quality issues related to ethanol used as a neat fuel (E85) are different, as the spectrum of evaporative and tailpipe emissions from neat fuels differs from those of blends. GHG emissions associated with ethanol used in blends and neat fuels are similar. While comparisons with MTBE are necessary, no attempt is made to present a comprehensive treatment of MTBE. Both ethanol and MTBE have desirable properties that contribute to clean gasoline, but there are some important differences between them. In particular, the growing detection of MTBE groundwater contamination has prompted a national debate about its continued use. MTBE imparts a turpentine odor and taste to water at very low concentrations1. ` ------------------------ Yahoo! Groups Sponsor ---------------------~--> Take the Yahoo! Groups survey for a chance to win $1,000. 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