RESEARCH INTERESTS - Biofuels
The substitution of biomass for oil as a feedstock for producing chemicals and liquid fuels has the potential for many economic and environmental benefits. Biomass-derived ethanol has made significant inroads into the transportation fuel sector, with an annual production of about 50-60 billion litres worldwide. However, the use of corn, wheat and sugar cane as feedstocks for fuel ethanol production, while defensible from the perspective of energy security and local economics, has come under fire due to questionable energy (and CO2) balances, as well as the ethical implications of using food crops for fuel production.
Using lignocellulosic materials as a feedstock does not compete with food crops, and has a number of additional benefits, including: a favourable energy balance, limited need for fertilization, and ability to grow on marginal land. As a result, many believe that it is inevitable that cellulosic feedstocks will eventually compete with agricultural materials as feedstocks for production of ethanol and other valuable products. To turn lignocellulosic feedstocks into ethanol, a number of processing steps are required, including pretreatment, hydrolysis, fermentation and product purification.
The major challenges identified for developing biorefineries include lowering costs and increasing product yields for: 1) biomass pretreatment; 2) biomass hydrolysis to sugar; and 3) fermentation. Advances have been made in all three areas recently. We have shown the promise of oxygen delignification for pretreatment of softwood-derived fibre. Others have reported order-of-magnitude decreases in enzyme costs, one of the main limiting factors. We have also reported the first successful application of a genetically- altered yeast to co-ferment glucose and xylose in an inhibitory industrial pre-hydrolysate. Our work is continuing, primarily aimed at improving pretreatment and fermentation.
CURRENT PROJECTS
- Ethanol production from bio-oil (pyrolysis oil)
- Ethanol production using urban waste cellulosic materials
- Pretreatment and hydrolysis of agricultural residues for ethanol production
- Modelling the role of lignin in hydrolysis of lignocellulosic materials
- Biological hydrogen production from lignocellulosics
- Algae production in tar sands tailings water
RECENT SELECTED PUBLICATIONS
- Jensen, A., Branion, B., Duff, S., and D. Posarac. The effects of black liquor dissolved solids, alkali lignin, and sodium salts on the vapour-liquid equilibrium of dimethyl sulphide in water. J. Pulp Paper Sci. (accepted Jan 2008).
- Bennett, N., Helle, S. and S. Duff. Extraction and hydrolysis of levoglucosan from pyrolysis oil. Appl. Microbiol. Biotechnol. (accepted April 2008).
- Liao, C., Finnbogason, T. and S.J.B. Duff. Treatment of logyard run-off with a continuous fixed film bioreactor. J. of Env. Engrg. and Sci. (accepted March 2008).
- Helle, S., Lin, T. and S.J.B. Duff. 2007. Optimisation of spent sulphite liquor fermentation. Enz. Microb. Technol. Enzyme and Microbial Technology 42(3): 259-264.
- Tao, W., Hall, K.J. and S.J.B. Duff. 2007. Microbial biomass and heterotrophic production of surface flow mesocosm wetlands treating woodwaste leachate: Responses to hydraulic and organic loading and relations with mass reduction. Ecol. Engrg. 31: 132-139.
- Helle, S., Bennett, N., Lau, K., Matsui, J., and S.J.B. Duff. 2007. A kinetic model for production of glucose by hydrolysis of levoglucosan and cellobiosan from pyrolysis oil. Carbohydrate chemistry 342:2365-70.
- Jensen, A., Branion, B., Duff, S., Pageau, G. and D. Posarac. 2007. Prediction of kraft mill total reduced sulphur emissions using vapour-liquid equilibrium theory. Pulp and Paper Can. 73. 108(6):41-46.
- Helle, S.S., Petretta, R. and S.J.B. Duff. 2007. Fortifying spent sulfite pulping liquor with hydrolyzed reject knots. Enzyme Microbial Technol. 41:44-50.
- Helle, S.S. and S.J.B. Duff. 2007. Effect of substrate variability on activated sludge kinetics during the treatment of bleached kraft mill effluent. J. Environ. Engrg. and Sci. 6:123-129.
- Hoy, P, D.R. Cameron, S.S. Helle, and S.J.B. Duff. 2006. Production of a recombinant protein using Pichia pastoris grown in evaporator condensate from a kraft pulp mill. Enzyme Microbial Technol. 38(3/4): 317-323.
- Helle, S.S., A. Murray, D.R. Cameron and S.J.B. Duff. 2004. Xylose fermentation by genetically-modified Saccharomyces cerevisiae 259 ST in spent sulphite liquor. Bioresource Engrg., 92:163-171.
- Charles, N., S. Mansfield, O. Mirochnik and S. Duff. 2003. The effect of oxygen delignification operating conditions on downstream enzymatic hydrolysis of softwood substrates. Biotechnol. Prog. 19(5): 1606-11.
- Helle, S.S., B. White, J. Lam, D.R. Cameron and Sheldon J.B. Duff. 2003. Effect of inhibitory compounds on growth and xylose fermentation by S. cerevisiae. Enzyme Microbial. Technol., 33:786-792.
TEACHING
- CHBE 373 - Water Pollution Control
- CHBE 364 - Environmental Engineering Laboratory
- APSC 150 - Engineering Case Studies
