Thursday, 17 May 2007 - 9:40 AM
209 (Pfahler Hall)

Breaking biological barriers to producing biofuels: Cellulosic ethanol and hydrogen

Y.-H. Percival Zhang, Virginia Polytechnic Institute & State University, Blacksburg, VA

Effectively releasing the locked polysaccharides from recalcitrant lignocellulose to fermentable sugars is among the greatest technical and economic barriers to realization of lignocellulose biorefineries because leading lignocellulose pretreatment technologies suffer from low sugar yields, and/or severe reaction conditions, and/or high cellulase use, narrow substrate applicability, and high capital investment, etc. A new lignocellulose pretreatment featuring modest reaction conditions (50C and atmospheric pressure) has been demonstrated to effectively fractionate lignocellulose to amorphous cellulose, hemicellulose, lignin, and acetic acid by sequentially using a non-volatile cellulose solvent (concentrated phosphoric acid), a highly volatile organic solvent (acetone), and water. The highest sugar yields after enzymatic hydrolysis were attributed to no sugar degradation during the fractionation and the highest enzymatic cellulose digestibility (~97% in 24 hours) during the hydrolysis step. Isolation of high-value lignocellulose components (lignin, acetic acid, and hemicellulose) would greatly increase potential revenues of lignocellulose biorefinery.

A novel enzymatic reaction was conducted for producing hydrogen from starch and water at 30C. The system contained 13 enzymes, 1 cofactor (NADP+), and phosphate, and water was cleaved by energy stored in starch according to the overall reaction: C6H10O5 (l) + 7 H2O (l) --> 12 H2 (g) + 6 CO2 (g). With technology improvement and integration with fuel cells, this technology would be suitable for mobile applications and also solves the challenges associated with hydrogen storage, distribution, and infrastructure in a hydrogen economy.

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