Investigation On The Production Of Ethanol From Paper Sludge By Simultaneous Saccharification And Fermentation

Paper sludge is solid waste from wastewater treatment of pulp and paper making mill, which consists of cellulose and hemicellulose. A study was taken up to determinate the composition of paper sludge and to esatablish simultaneous saccharification and fermentation (SSF) and simultaneous saccharification and co-fermentation (SSCF) using paper sludge, yeast and commercial cellulase. Ethanol production from paper sludge using SSF and SSCF were investigated.The moisture content of wet chemical pulping sludge was 72.70%, pH value was 7.6; the average ash in dried sludge was 38.32%, protein was 1.52% and fat was 2.74%. Based on the amount of glucose and xylose present after dilute acid hydrolysis, the amount of cellulose and hemicellulose was estimated to be 25.77% and 5.86% respectively. The moisture content of wet deinking paper sludge was roughly 41.47%, pH value was 7.6, and the composition of the dried deinking paper sludge was determined to be: 43.96%ash, 11.99%cellulose, 3.92% hemicellulose, 1.78%protein and 1.11%fat. The characteristics of Saccharomyces cerevwasiae SHY08-3 and fusion SHY07-1 were investigated.The results showed that the culture with 18-21h was suitable inoculum.The experiment results showed that commercial cellulase can be used for SSF without filtration sterilization. Chemical pulping sludge had good enzymability and fermentability, whereas deinking paper sludge was not susceptible to cellulase. The maximum ethanol production efficiency of chemical pulping sludge and deinking paper sludge, 95.97% and 72.71% respectively, were reached at 72h of fermentation under the conditions of substrate concentration of 35g/L (according to cellulose), cellulase loading of 55FPU/gEC(effective cellulose), inoculum size of 6%, temperature of 37℃and rotation speed of 200rpm.The optimum technical conditions for ethanol production using SSCF were as follows: pH6, temperature 30℃, substrate concentration 40g/L, cellulase loading 40FPU/gEC. Under such conditions, the final ethanol concentration was 14.80g/L, and ethanol production efficiency was 65.96%. The orthogonal design was used for estimating significance of the factors for ethanol production. The results showed that cellulase loading was the most significant factor, and substrate concentration and fermentation temperature had significant effect on ethanol production too. However, inoculum size had no significant effect on ethanol production. Compared to SSF, SSCF had certain advantages at the same substrate concentration and enzyme loading, but it needed to improve the ability of fusion yeast SHY07-1 to utilize glucose.The semicontinuous fermentation made more paper sludge utilized for ethanol production at lower enzyme loading than batch fermentation. The concentration of ethanol increased twice after semicontinuous fermentation and the concentration reached 32g/L. Meantime, byproducts were no longer increased in semicontinuous fermentation and maintained at low concentration.