UBC Theses and Dissertations
Ethanol production from bio-oil Chan, Jacky
Bioethanol is often viewed as one of the solutions to the tight gasoline supplies in North America. Although bioethanol is already available in the market, there are a number of problems associated with the current processes for the production of bioethanol. The current bioethanol production processes are often referred as first generation bioethanol production processes. For these first generation processes, the feedstocks for production are usually energy crops. The most common energy crops in North America are corn and wheat. The use of these energy crops has triggered debates on the problems associated with using food sources to create energy and the uptake of agricultural land to produce energy. In this project, an alternative feedstock for bioethanol is investigated. The feedstock used in the project is bio-oil, which can be derived from any biomass waste. An advantage of using bio-oil is that it is not derived from food crops but instead waste material is being converted into energy. The objective of this study was to determine the technical viability of producing bio ethanol using bio-oil as a substrate for fermentation. In order to maximize the ethanol yield, the extraction of levoglucosan with water was optimized and a number of detoxification techniques for inhibitor removal were evaluated. This report provides a technical overview of conditions evaluated for extracting levoglucosan from bio-oil, and methods used for improving the fermentability of bio-oil hydrolysate by detoxification. The techniques used in an attempt to improve the fermentability of bio-oil hydrolysate include: adsorption, overliming, solvent extraction, and hydrogenation. In addition, a biological approach called adaptive evolution was used to aid the yeast to adapt to the inhibitory environment of bio-oil hydrolysate in order to increase their resistance to inhibitors. The optimal condition for aqueous extraction of levoglucosan from bio-oil was found to be 1:1 (mass water to mass bio-oil). It was found that the temperatures examined (25°C and 80°C) had minimal effect on the amount of levoglucosan extracted. Among the detoxification techniques tested, it was found that overliming and solvent extraction were able to improve the fermentability of bio-oil hydrolysates. Overliming was able to increase the yield of ethanol from bio-oil hydrolysate by 0.19±0.01 (g ethanol/g glucose) at 50% strength hydrolysate and 0.45±0.05 (g ethanol/g glucose) at 40% strength hydrolysate. A number of extractants were examined and the three best solvents were 25% volume of tri-n-octylamine with co-solvent 1-octanol, 50% volume of alamine 336 with co-solvent 1-octanol and oleyl alcohol. These three solvents were able to selectively remove at least 84 — 93% of acetic acid, which was the targeted inhibitor in bio-oil hydrolysate. In addition, a technique called adaptive evolution of yeasts was applied, which was capable of increasing the ethanol yield by at least 6% when compared with the unadapted parental strains.
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