Feedstock cost is predicted to be the largest contributor to overall cost for the biorefinery and this percentage will only increase as the industry matures. Because of this, finding diverse sources of inexpensive, highly digestible materials is very important for the success of the industry. Compared to conventional agriculture, low-input mixed-species feedstocks such as biomass from native prairie grasslands, require minimal agronomic inputs and maintenance, and provide more valuable ecosystem services.  However, these fields may not produce the high yields necessary to be economically competitive.  To this point, most research on energy generation from mixed-species feedstocks has focused on thermochemical conversion methods and, although various groups have predicted the ethanol yield from biochemical conversion, there has been no experimental research to analyze this method.  One benefit of the biochemical conversion route over the thermochemical is the potential to alternatively use pretreated biomass produced from these fields as a higher value animal feed.

In order to investigate the feasibility of using low-input mixed-species feedstocks for biofuel and animal feed production, we tested five replicates (fields) of differing species composition from the old field treatment of the Great Lakes Bioenergy Research Center (GLBRC) intensive field site.  Ammonia fiber expansion (AFEX) pretreatment followed by either enzymatic hydrolysis or in vitro rumen digestibility were performed on these samples in order to determine their value as both a biofuel feedstock and an animal feed compared to untreated material.  An economic analysis from the perspective of the biorefinery was also conducted and the results were compared to corn stover.  The results indicate that the biorefinery economics depend heavily on the overall sugar content and the digestibility of the feedstock, which in turn is dependent on the species composition.