Sunday, May 4, 2008
1-15

Ethanol Production as a Supplementary Unit in Kraft Paper Mill

Li Kang, Wei Wang, and Y.Y. Lee. Chemical Engineering, Auburn University, 212 Ross Hall, Auburn, AL 36849

Kraft paper mill produces chemical pulp treating wood chips with white liquor, a mixture of sodium hydroxide, sodium sulfide, and sodium carbonate at 130 - 180 ºC. The long fibers of pulp are used for paper making. The short and fine fibers that are rejected in paper making process and eventually become waste material, e.g., paper mill sludge. Due to its high carbohydrate, low lignin, and low ash content, the pulp can be an attractive substrate for bioconversion into various products, one of which is cellulase. Kraft paper mill thus offers substrates for production of cellulase enzyme as well as  cellulosic ethanol. Our laboratory data indicate that only about 10 kg of Kraft pulp is required to produce cellulase enzyme that can saccharify one dry-ton of the sludge. In this study, the Kraft pulp was used as the main carbon source for production of cellulase by Trichoderma Reesei, Rut C-30. Partially de-ashed Kraft paper mill sludges were tested as a substrate for production of cellulosic ethanol through fermentation using the cellulase procduced in-house and two different microorganisms -recombinant E. coli KO-11 and Saccharomyces cerevisiae D5A. Fermentation process proceeded without any major problems and demonstrated ethanol yields comparable to those of pretreated corn stover. It is projected that 70 gallons of ethanol can be produced from these processes per ton of dry sludge.

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