AGRO 148

Developing herbaceous energy crops as feedstocks for bioethanol production

Bruce S. Dien, dienb@mail.ncaur.usda.gov1, Michael A. Cotta, cottama@ncaur.usda.gov1, Hans-Joachim G. Jung, jungx002@umn.edu2, and Kenneth P. Vogel, kpv@unlserve.unl.edu3. (1) Fermentation Biotechnology Research Unit, USDA-Agricultural Research Service, National Center for Agricultural Utilization Research, 1815 N. University Street, Peoria, IL 61604, (2) Plant Science Research Unit, USDA-Agricultural Research Service, 411 Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN 55108-6026, (3) Grain, Forage, and Bioenergy Research Unit, USDA-Agricultural Research Service, 344 Keim Hall, East Campus, Lincoln, NE 68508
Perennial herbaceous crops with high biomass yields are promising substrates for producing bioethanol. A variety of biomasses including cool and warm season grasses and a legume are being evaluated for this purpose. As a first approach, biomass materials were pretreated with dilute sulfuric acid and either converted to sugars by solely adding commercial cellulase preparations or to ethanol by co-adding Saccharomyces cerevisiae. Sugar and ethanol yields were influenced by both plant type and harvest maturity. Conversion efficiency was found to decrease and carbohydrate content to increase with maturity. Also, alfalfa stem was more recalcitrant than other sources of biomass tested to pretreating with dilute acid. A critical issue found for herbaceous biomass was the relatively high amounts of soluble sugars compared to other sources of biomass. It was determined that treating with dilute acid may be impractical as the pretreatment converts these sugars to furans which inhibit the subsequent yeast fermentation. Currently, other pretreatment methods are being explored that are more amendable to preserving these sugars.