UBC Theses and Dissertations

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UBC Theses and Dissertations

Potential for ethanol from urban cellulosic wastes Leung, Clara


Ethanol fuel can be used as a substitute for gasoline. It can be produced from numerous sources. There are several environmental and economic benefits associated with this feedstock; its abundant availability worldwide, the reduction of landfill space, and the production of a valuable, clean liquid fuel that when utilized. The successful bioconversion of urban cellulosic waste into ethanol will provide industries with an inexpensive raw material for ethanol production and a more competitive ethanol price. The objective of this project is to investigate whether it is technically- and economically-viable to use urban cellulosic wastes as a feedstock for a full-scale ethanol plant. The urban cellulosic wastes evaluated include: grass, cardboard, and pulp mill clarifier sludge with switchgrass being the control. In order to maximize the ethanol yield from the urban cellulosic wastes, conditions for pretreatment and enzymatic hydrolysis were optimized. After the optimal condition for each substrate was determined, the hydrolysate from each condition was subjected to fermentation with Saccharomyce cerevisiae (S. cerevisiae) K1 strain. In order to evaluate the efficiencies of oxygen delignification, the pretreatment used in this study, and enzymatic hydrolysis, the compositions (lignin, pentose and hexose) of the substrates that were not pretreated and pretreated at different temperatures were determined by acid hydrolysis. By comparing the lignin contents of non-pretreated substrates from acid hydrolysis to those that were reported in literature, they are out of range. Therefore, all the lignin contents determined from acid hydrolysis will not be used for any calculation. However, these lignin values have indicated that oxygen delignification is effective on switchgrass, grass and pulp mill clarifier sludge since their lignin contents reduced when the substrates are pretreated. Although oxygen delignification is not as effective for cardboard, the non-pretreated cardboard that was hydrolyzed at 10 g dry substrate/L and 40 FPU/g dry substrate has the highest sugar yield (6.12 g sugar/10 g dry substrate) among all substrates tested in all pretreatment and hydrolysis conditions. After the hydrolysate obtained from the hydrolysis of cardboard was subjected to fermentation, it has an ethanol yield of 0.32 gram of ethanol per each gram of sugar.

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