Monday, May 4, 2009
9-55
Quantifying Livestock Feed Value of AFEX-Treated DDGS and Subsequent Biorefinery Byproducts
With annual U.S. production of fuel ethanol at nearly 9 billion gallons, coupled with the Renewable Fuels Standard, supplies of coproducts such distillers dried grains with solubles (DDGS) are anticipated to continue to grow for the next several years. DDGS is used as livestock feed. But as supplies of this coproduct grow, it will become increasingly important to investigate opportunities to improve its value and utilization. Ammonia Fiber Expansion (AFEX) is a process that has been shown to improve the nutritional qualities of feedstuffs, and it may play a role in developing corn-based biorefineries using existing ethanol plants. Toward that end, the objective of this study was to investigate the effects of AFEX-treatment and subsequent biorefining on the resulting feed quality of DDGS. During AFEX treatment, samples of DDGS were subjected to ammonia loadings at a rate of 1:1, at 90oC, for 30 min. Portions of both untreated DDGS and AFEX-treated DDGS were then fermented, using SSF, at 20% loading using Saccharomyces cerevisiae in order to produce ethanol. Nutritional composition was determined on all samples (untreated DDGS, AFEX-treated DDGS, and fermentation residues) in order to quantify their values as livestock feed. Analyses included proximate compositions (crude protein, lipid, ash), acid detergent and neutral detergent fiber, amino acid and fatty acid profiles, macro/micro mineral compositions, and in-vitro dry matter digestibility. Determining the value of resulting coproducts will be crucial in helping guide the development of biorefineries; their sale and utilization will be key to achieving economic sustainability.
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