Location: Bioenergy ResearchTitle: Comparison of cellulosic ethanol yields from midwestern maize and reconstructed tallgrass prairie systems managed for bioenergy Author
Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2014
Publication Date: 6/26/2014
Publication URL: http://handle.nal.usda.gov/10113/62007
Citation: Nichols, V.A., Miguez, F.E., Jarchow, M.E., Liebman, M.Z., Dien, B.S. 2014. Comparison of cellulosic ethanol yields from midwestern maize and reconstructed tallgrass prairie systems managed for bioenergy. BioEnergy Research. 7:1550-1560. Interpretive Summary: Perennial grasses with high biomass yields are predicted to be significant feedstocks for production of chemicals and biofuels from lignocelluloses. In the past, perennial grass production has been gauged on sub-par farmland. This study addressed the question: how does the production of diverse prairie compare to continuous maize for cellulosic biomass on fertile fields? In this study, production quality land was used for cultivation of a diverse prairie biomass side by side with continuous maize. As part of the experiment, prairie fields were cultivated with and without spring nitrogen fertilization. Fields were grown from 2009-2013. Biomass production was highest for the fertilized prairie followed by unfertilized prairie followed by continuous maize. The biomass collected was examined for composition and it was determined that theoretical ethanol yields from the fertilized prairie field was 1790 L/ha/yr. This study will be of interest to those interested in sustainable land use and advanced biofuels.
Technical Abstract: Maize- and prairie-based systems were investigated as cellulosic feedstocks by conducting a 9 ha side-by-side comparison on fertile soils in the Midwestern United States. Maize was grown continuously with adequate fertilization over years both with and without a winter rye cover crop, and the 31-species reconstructed prairie was grown with and without spring nitrogen fertilization. Both maize stover and prairie biomass were harvested in the fall. We compared amounts of cellulosic biomass produced and harvested, carbohydrate contents as measured by both dietary and detergent methods, and estimated cellulosic ethanol yields per hectare. From 2009-2013, the cropping system with the largest non-grain biomass yield was fertilized prairie, averaging 10.4 Mg ha-1 yr-1 aboveground biomass with average harvest removals of 7.8 Mg ha-1 yr-1. The un-fertilized prairie produced 7.4 Mg ha-1 yr-1 aboveground biomass, with average harvests of 5.3 Mg ha-1 yr-1. Lowest cellulosic (non-grain) biomass harvests were obtained from continuous maize systems, averaging 3.5 Mg ha-1 yr-1 when grown with, and 3.7 Mg ha-1 yr-1 when grown without a winter rye cover crop, respectively. Un-fertilized prairie biomass and maize stover had equivalent dietary-determined potential biomass ethanol yields at 330 g ethanol kg-1 dry biomass, but fertilized prairie was lower at 315. The detergent method did not accurately capture these differences. Over the five year period of the experiment, un-fertilized and fertilized prairie systems averaged 810 and 1790 L potential cellulosic ethanol ha-1 yr-1 more than the maize systems, respectively. Differences in harvested biomass accounted for >90% of ethanol yield variation.