Bryan D. Bals, Department of Chemical Engineering and Material Science, Michigan State University, 2527 Engineering Building, East Lansing, MI 48824, Bruce Dale, Chemical Engineering and Materials Science, Michigan State University, 3900 Collins Rd, Lansing, MI 48910, and Michael Allen, Department of Animal Science, Michigan State University, 2265 Anthony, East Lansing, MI 48824.
As commercial cellulosic ethanol becomes a reality, concerns regarding land use are becoming increasingly prevalent. Critics claim a large cellulosic ethanol industry will result in decreased land available for food production, leading to increased food prices as well as increased carbon emissions due to indirect land use change. However, these concerns assume a “business as usual” approach to farm management. If bioenergy is to become a significant portion of agriculture, then it is likely that the animal feed market will be adapted to reflect these changes. Dedicated energy crops such as switchgrass have the potential to produce more carbohydrates and protein per acre than corn and soy, respectively, thus leading to the possibility that these crops could be integrated into animal feed rations. These feed co-products could be produced on-site at the biorefinery, or more likely at a regional biomass processing center (RBPCs).We propose several methods for integrating animal feed production with cellulosic ethanol from switchgrass using ammonia fiber expansion (AFEX) pretreatment technology. AFEX-pretreated fiber can significantly increase the digestibility and feed quality of grasses, and thus potentially compete with more traditional energy feeds. Extracting proteins from grasses prior to pretreatment as well as recovering proteins after hydrolysis and fermentation will also be considered. Of particular importance is the quality and digestibility of the proteins, particularly for the essential amino acids. The potential for producing animal feed co-products is considered for both on-site production as well as at RBPCs, and the consequences of each taken into account.
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