VIEWS: 14 PAGES: 5 CATEGORY: Science & Technology POSTED ON: 6/26/2010
[...] 20 plants are currently under construction or are undergoing expansion, all of which will contribute an additional 1.8 billion gallons/yr (6.8 billion liters/yr). Because of the dynamics of the free market economy, the growing quantity of co-products that will be produced as me industry continues to expand may substantially influence the future of die industry.
inform December 2009, Vol. 20 (12) 789 Processing Distillers’ dried grains with solubles (DDGS)—A key to the fuel ethanol industry Kurt A. Rosentrater Modern societies face many challenges, includ- ing growing populations and increasing demands for food, clothing, housing, and consumer goods and for the concomitant raw materials and energy required to produce all of these. Additionally, there is an overwhelming reliance on fossil fuels for energy. Transportation fuel accounted for 28% of all energy consumed in the United States during 2008, 95% of which came from petroleum sources. And domestic production of crude oil was 4.96 FIG. 1. A typical dry-grind corn-to-ethanol manufacturing plant. million barrels per day, whereas imports were 9.76 studies include Kaltschmitt et al. (1997), Kim and Dale (2004), million barrels per day (nearly two-thirds of the Pimentel and Patzek (2005), Shapouri et al. (2003), and Sheehan total US demand). et al. (2004). Farrell et al. (2006) presented a thorough review Biofuels, which are renewable sources of energy, can help and synthesis of this debate. However, new questions have arisen, meet some of these increasing needs. Potentially, they can be pro- including water consumption and land use change. Answers are duced from a variety of biomass materials, including agricultural now being developed. residues, corn stover, grasses, and legumes. Cur- rently, however, corn grain is the most heavily used feedstock in the United States, because alcohol production from corn is readily accom- plished at a lower cost compared to other biomass substrates. The corn-based fuel ethanol industry is well poised to help extend and augment the nation’s supply of transportation fuels. And, over the last decade, many innovations have occurred in the industry, not only in production processes used and final products produced but also in terms of optimizing raw materials and energy consumed. Due to many advantages, including lower capital and operating costs (including energy inputs), most new ethanol plants are dry grind facilities (Fig. 1), as opposed to the older style wet mills (see also inform 18:658–660, 2007). Questions regarding the energy balance of ethanol, especially about resource and energy inputs and outputs, economics, impacts of manu- facture, and the performance of ethanol in vehi- FIG. 2. Trends in production of fuel ethanol and generation of DDGS (distillers dried cles, have led to many Life Cycle Assessment grains with solubles). RFS denotes the mandate due to the Renewable Fuel Standard studies to examine the overall costs and benefits (adapted from Renewable Fuels Association, Washington, DC, 2009; available online of this biofuel. Examples of the more prominent at www.ethanolrfa.org) DEC 09 INFORM.indd 789 12/2/09 3:15:59 PM 790 inform December 2009, Vol. 20 (12) To help meet the demand for more motor fuel, the number of US ethanol plants has risen rapidly in the past 15 years, as has the quantity of fuel ethanol produced (Fig. 2). As of July 2009, 197 manufacturing plants in the United States have an aggregate production capacity of over 12.7 billion gallons/year (48.1 billion liters/yr). Moreover, 20 plants are currently under construction or are undergoing expansion, all of which will contribute an additional 1.8 billion gallons/yr (6.8 billion liters/yr). As pro- duction volume increases, the processing residues (known a
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