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Poster Presentation 1-32
The Impact of Cotton Gin Processing on Feedstock Properties and Ethanol Production
Foster A. Agblevor
Virginia Polytechnic Institute and State University Department of Biological Systems Engineering, 212 Seitz Hall, Blacksburg, Virginia 24061
Telephone: (540) 231-2578; Fax: (540) 231-3199; E-mail: fagblevo@vt.edu
Cotton gin waste was collected from five cotton gins and characterized for summative composition. The composition of the raw feedstock varied within and between cotton gins. The ash contents ranged from 7.9 to 14.6% and the acid insoluble material ranged from 18 to 26%. The xylan content ranged from 4 to 15% while the cellulose content ranged from 20 to 38%. The large variations in feedstock compositions were attributed to the age of the feedstocks, processing methods, and handling of the cotton gin waste.
The recovery of fiber was 82.5% and 81.6% for steam explosion pretreatment at severity 3.5 and 4.5 respectively. The extractives content increased with severity of treatment and, at severity 4.5, was twice that obtained for the untreated material. The acid insoluble material content also increased between 54 to 94% relative to the untreated material. A large fraction of the hemicellulosic component was lost either through solubilization or degradation during steam explosion. The residual fiber was mostly cellulose. The enzyme hydrolysis rate during the first five hours for the steam-pretreated material was twice that for the untreated material. However, the hydrolysis appeared to be a two-phase phenomenon because of the feedstock heterogeneity. The cotton fiber hydrolyzed very rapidly, while the lignocellulosic fraction was very slow.
Overlimed steam-exploded cotton gin waste was readily fermented to ethanol by the Eschericia coli KO11. The ethanol yields were feedstock and severity dependent and ranged from 58 to 92.5% of the theoretical yields. The feedstock from the Suffolk cotton gin produced 191 L (50 gal) per ton whereas that from the Wakefield gin produced 120 L per ton for severity 3.5. At severity 4.5, the ethanol yield for the Suffolk feedstock decreased by 76%.
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