Sunday, May 4, 2008
3-33

Alkaline pretreatment of Switch grass

Rajesh Gupta and Y. Y. Lee. Department of Chemical Engineering, Auburn University, 207 Ross Hall, Department of Chemical Engineering, Auburn, AL 36849

Switch grass is one of the most promising feedstocks for cellulosic ethanol production. In this study, two alkaline reagents, aqueous ammonia and NaOH, were investigated for pretreatment of switch grass. In the case of ammonia based treatment, two different types of pretreatment modes were applied: ammonia recycle percolation (ARP) and soaking in aqueous ammonia (SAA). The ammonia based processes were proven to be highly effective in delignification, yet the enzymatic digestibility of treated switch grass with cellulase did not met the expectation. The lignin content of untreated switch grass was high (26.4%). It appears that the residual lignin content is the major hurdle limiting the accessibility of cellulase, thus the enzymatic digestibility even after pretreatment of switch grass with these processes. In order to further increase the delignification, H2O2 was added in the SAA and NaOH treatment. Addition of H2O2 significantly increased delignification and digestibility of switch grass. Addition of xylanase as a supplementary enzyme was highly effective in improving the digestibility of treated switch grass. Lignin separated from the pretreatment was characterized by TGA, DSC and FTIR. The data from these tests were further analyzed to understand the reaction mechanism.  

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