![]() ![]() ethanol plants conducted in 2008 reported average ethanol yield of 100 gallons per dry ton (Mueller, 2010).ĭDGS is a coproduct of grain ethanol production. The theoretical yield of converting corn starch to ethanol is 112 gallons per dry ton (Patzek, 2006). The residue can be marketed wet as a dairy or cattle feedstuff or as dried distillers grain with solubles (DDGS) as a dairy, cattle, swine, and poultry feedstuff (Schwietzke et al., 2008). The fermented mash is separated into ethanol and residue by distillation ( Figure 2-2). The 6-carbon sugars are then fermented to ethanol by natural yeast and bacteria. Most corn is dry milled-that is, the grain is ground to a meal, and then the starch from the grain is hydrolyzed by enzymes to glucose. ![]() Starch from grains can be converted to ethanol by biochemical pathways. An advantage of grains as biofuel feedstock is that they are relatively dense and efficient to store and transport have well-established production, harvest, storage, and transport supply chains or systems and are commodity crops with well-established grades and standards that facilitate marketing and trading.įIGURE 2-1 Distribution of planted corn acres in the United States in 2008. The national average reached 165 bushels per acre in 2009 and was 156 bushels per acre in 2010. Corn yield in the United States has been increasing over recent decades (Cassman and Liska, 2007). The majority of corn acreage is found in the Midwest ( Figure 2-1). Other feedstocks and conversion technologies that are not likely to be deployed by 2022 also are discussed.Īs of 2010, the primary feedstock for biofuel produced and consumed in the United States was corn grain. This chapter examines the supply chains of food-based biofuels that are produced and nonfood-based biofuels that are likely to be produced in the United States within the 2022 timeline as established by the Renewable Fuel Standard amended by the Energy Independence and Security Act of 2007 (RFS2). Each subsequent stage of biofuel production and use could incur positive or negative effects on the economics of producing biofuels, the economic effects on other sectors, and the environment. These differing conditions contribute to a range of economic costs for feedstocks and environmental effects. Biomass is procured from diverse environments, each associated with different economic costs for production and collection. The biofuel supply chain involves producing biomass feedstock harvesting, collecting, storing, and transporting the feedstock to the biorefinery converting the biomass to fuel at the biorefinery distributing biofuels to end users and, finally, using the fuel. ![]()
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