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Factors affecting the enzymatic hydrolysis of primary clarifier sludges

University of British Columbia

Bioconversion of cellulose to ethanol, by means of enzymatic hydrolysis, has been, and still is, the focus of much research interest since the early 1980s. The enzymatic hydrolysis process is well developed and offers an environmentally attractive option. However, many obstacles prevent the process from becoming commercially attractive. These obstacles include kinetic inhibitions (competitive reactions with lignin, intermediate and end-product inhibitions), difficulties in enzyme recycling, and economics. These hurdles have resulted in intense research over the last several decades. Despite the economic disadvantages of the enzymatic hydrolysis process, niche opportunities, such as the operations at the Tembec mill in Temiscaming, Quebec, still exist. The ethanol produced from its spent sulphite liquor is distilled to food-grade ethanol, which demands higher prices than fuel ethanol. Additional ethanol produced from Tembec's waste primary clarifier sludge (PCS), using enzymatic hydrolysis, could also be sold for similar use. This work explored several aspects of enzymatic hydrolysis to optimise the production of ethanol from Tembec's sulphite PCS. Batch hydrolysis results indicated that up to 50% of the PCS was hydrolysable by Trichoderma reesei enzymes. Adsorption experiments revealed that a significant fraction of enzyme activity was recoverable in the liquid hydrolysate. Oxygen delignification, as a pretreatment option for the PCS, was also examined. It was found that on a mass basis, a 68% increase in sugar yield from delignified PCS was possible over untreated PCS. A semi-continuous laboratory-scale hydrolysis reactor (22 L working volume) was run on both untreated and oxygen delignified PCS. In both cases, the yields represented 90% of the levels attained by batch hydrolysis.

Thesis/Dissertation

application/pdf

2009-05-26

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http://hdl.handle.net/2429/8282

Chemical and Biological Engineering

University of British Columbia

UBCV

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