Feedstock Yield and Quality of Three Bioenergy Production Systems in Oklahoma.

Biomass based biofuel production has emerged as one of the major approaches towards achieving energy independence. However, the successful development of biofuel from feedstock depends on the ability produce high yields and acceptable quality in harsh environmental conditions.  Therefore, the objective of this study was to evaluate the effect of N fertilization on feedstock yield and quality from three bioenergy production systems. Variable biomass yield was generated by supplying N at different rates (hairy vetch (Vicia villosa Roth), 0, 84,168, and 252 kg N ha^-1) in a field plot study at Stillwater, Oklahoma. Plots were planted with switchgrass “Alamo” (Panicum, virgatum L.), high biomass sorghum (Sorghum bicolor) and mix grasses (Indian grass (Sorghastrum nutans), big bluestem (Andropogon gerardii) and Switchgrass “Alamo”) in a split plot design with three replications. Main plot was the crop species and sub-plot the nitrogen treatments.  Nitrogen was applied in the spring, hairy vetch planted in the spring and biomass harvested in fall after killing frost. Feedstocks were analyzed for lignin, cellulose, hemicellulose and nitrogen content. Feedstock cellulose and hemicellulose content varied with production system, while biomass yields varied in response to nitrogen rate only. Nitrogen and lignin content was affected by both production systems and nitrogen rates independently. The highest overall biomass yield (5.5 Mg ha^-1) was achieved without N fertilization and the lowest (3.2 Mg ha^-1) with 252 kg N ha^-1. Higher lignin, cellulose and hemicellulose content were observed in switchgrass and mix grass systems, while sorghum had the highest N content in the biomass. Nitrogen content showed a quadratic trend with N fertilizer rate, while biomass yield and lignin content both followed a decreasing linear trend with fertilizer rate. The severe drought condition of 2011 that affected the state of Oklahoma contributed to the lack of fertilizer response.  However, despite the environmental condition, these results do suggest that biomass quality may differ among production systems.