Improved, High-Moisture Ensiled Crop Feedstocks for Cellulosic Ethanol

As grain ethanol production capacity becomes constrained by the available supply of corn grain, the use of lignocellulosic biomass will become necessary for meeting the surging demand for fuel ethanol. However, the cost of biomass pretreatment and enzymatic hydrolysis makes cellulosic ethanol too expensive. In 2006, the U.S. Department of Energy released a ¿Joint Biofuels Roadmap¿ that outlines technical goals for achieving low-cost production of cellulosic ethanol. Two crucial goals are the reduction of: (1) the substantial capital and operating cost of pretreatment to remove lignin and hemicellulose, and (2) the cost of cellulase enzymes used to hydrolyze cellulose into fermentable sugars. Although these costs now range from $1.00 to $2.00 per gallon, they could fall to $0.10 to $0.25 per gallon in large scale production, with even lower costs desirable to improve ethanol¿s cost competitiveness with fossil fuels. This project addresses both of these goals by seeking to improve the quality of ensiled biomass, so as to reduce downstream pretreatment and hydrolysis costs. Past research has demonstrated that inoculating ensiled biomass with cellulases and other enzymes can increase saccharification (sugar content) and digestibility, thereby improving feed quality for livestock. By engineering energy crops to express such enzymes in plant tissues, activated by ensilement, a substantial reduction in pretreatment requirements and exogenous enzyme use is believed possible, with projected cost savings up to $1.00 per gallon. Commercial Applications and other Benefits as described by the awardee: The successful completion of this project should lay the foundation for improved biomass feedstocks for cost-effective production of ethanol, butanol, and other renewable fuels, leading to reduced downstream processing costs.