ARS | Publication request: Production of Butanol (a Biofuel) from Agricultural Residues: Part II - Use of Corn Stover and Switchgrass Hydrolysates

Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 28, 2009
Publication Date: February 1, 2010
Citation: Qureshi, N., Saha, B.C., Hector, R.E., Dien, B., Hughes, S., Liu, S., Iten, L., Bowman, M.J., Sarath, G., Cotta, M.A. 2010. Production of butanol (a Biofuel) from agricultural residues: Part II - Use of corn stover and switchgrass hydrolysates. Biomass and Bioenergy. 34(4):566-571.

Interpretive Summary: In these studies, we were able to convert corn stover hydrolyzate to butanol. This is important because butanol is a superior biofuel to ethanol and can be produced using microbial cultures from glucose or corn. Unfortunately, the high cost of these substrates (glucose or corn) make butanol’s production cost inefficient. Prices of corn stover and switchgrass have been in the range of $50-60/ton as opposed to corn which has ranged from $133-230/ton during recent months. For this reason, economically available substrates such as corn stover and switchgrass should be used. Both corn stover and switchgrass were hydrolyzed to simple sugars using dilute acid pretreatment and enzymatic hydrolysis. In these studies, we were able to produce more butanol (26.27 g/L) from corn stover than from glucose (21.06 g/L). Fermentation of switchgrass hydrolyzate to butanol was difficult as it contained inhibitors that prevented fermentation. This research will benefit U.S. farmers who grow corn and switchgrass and the U.S. transportation industry.

Technical Abstract: Acetone butanol ethanol (ABE or AB, or solvent) was produced from hydrolyzed corn stover and switchgrass using Clostridium beijerinckii P260. A control experiment using glucose resulted in the production of 21.06 gL**-1 total ABE. In this experiment, an AB yield and productivity of 0.41 and 0.31 gL**-1h**-1 was achieved, respectively. Fermentation of untreated corn stover hydrolyzate (CSH) exhibited no growth and no ABE production; however, upon dilution with water (two fold) and wheat straw hydrolyzate (WSH, ratio 1:1), 16.00 and 18.04 gL**-1 ABE was produced, respectively. These experiments resulted in AB productivity of 0.17 - 0.21 gL**-1h**-1. Inhibitors present in CSH were removed by treating the hydrolyzate with Ca(OH)2 (overliming). The culture was able to produce 26.27 gL**-1 ABE after inhibitor removal. Untreated switchgrass hydrolyzate (SGH) was poorly fermented and the culture did not produce more than 1.48 gL**-1 ABE which was improved to 14.61 gL**-1. It is suggested that cultures that can metabolize or tolerate inhibitors and still produce AB be developed.