Progress 12/15/07 to 06/30/09
Outputs
OUTPUTS: We investigated the potential of producing ethanol from municipal waste in Washington State. We divided the municipal waste into three primary streams and then investigated the potential of converting each into ethanol. This division was made to provide a more fundamental understanding of the issues associated with conversion for each of the major streams. The three primary streams were mixed waste paper, yard waste, and municipal solid Waste. For each stream, an experimental study was done to investigate conversion of the biomass into ethanol using bioconversion processes. This experimental work was then accompanied by a Life Cycle Assessment (LCA) to determine the overall environmental impact of the proposed processes. ASPEN models of biorefineries were developed to provide process data for the LCA. An assessment of economic viability was also performed based on the ASPEN models. PARTICIPANTS: Rick Gustafson, Professor, University of Washington College of Forest Resources. Renata Bura, Assistant Professor, University of Washington College of Forest Resources. Joyce Cooper, Associate Professor, University of Washington Department of Mechanical Engineering. Ryan McMahon, undergraduate student, University of Washington College of Forest Resources. Elliott Schmitt, graduate student, University of Washington Department of Mechanical Engineering. Azra Vajzovic, Research Scientist/Engineer, University of Washington College of Forest Resources. TARGET AUDIENCES: Target audiences include the Washington State Department of Ecology and other governmental agencies, waste management professionals, biorefineries, engineers, educators, researchers, students, and the general public. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
1. Process Development: Paper, yard and municipal solid waste are sugar rich lignocellulosic feedstocks. Dilute acid hydrolysis is an effective pretreatment method for paper and municipal solid waste. Steam pretreatment is a good pretreatment method for fractionation of yard waste. The water insoluble fractions of municipal solid and paper waste are easily hydrolysable by enzymes. Almost theoretical cellulose to glucose conversion was achieved. The water insoluble fraction of yard waste is difficult to hydrolyze by enzymes. However, the low cellulose to glucose conversion yields were expected since the biomass was composed of mixture of branches, wood chips, bark, and needles. The results obtained during this study also demonstrate that PTD3 was able to very efficiently convert yard waste hydrolysate to ethanol with a yield 100% of theoretical during the fermentation process. Pretreated and hydrolyzed sugars of municipal solid, paper and yard waste are readily fermentable by yeast. High ethanol yields were obtained (100% of theoretical). Overall ethanol yields of 110 gallons/ton, 90 gallons/ton, and 40 gallons/ton are estimated for municipal solid waste, paper waste, and yard waste respectively. 2. Life Cycle Assessment: a. Municipal solid waste seems to offer the greatest potential as both a waste management strategy and for bio-fuel production. With over 4 million metric tons of MSW generated in 2007, there is enough lignocellulosic material available to meet the demands of a large capacity biorefinery within the State. b. The greatest contributor to ethanol production environmental flows is chemicals production, specifically lime production. On the other hand, avoidance of dry-mill corn ethanol greatly reduces the environmental flows for ethanol production. c. Landfilled waste offers the least benefit overall, even with production of electricity and avoidance of Washington electric grid. This is related to the fact that the Washington electric grid is largely dominated by clean hydropower and offers little benefit from avoidance. It is recommended that biofuel production from lignocellulosic rich MSW should be pursued over the other waste streams. Mixed waste paper, although has benefits for ethanol production, seems to have greater benefits for replacing virgin pulp. Likewise yard waste seems to offer greatest benefits as a compost than as solely as an ethanol fuel source. It is also possible that some combination of the waste streams be used. Overall the economic analysis suggests that conversion of municipal waste is economically viable. Further economic analysis would be required, however, for a more definitive conclusion.
Publications
- Gustafson, R., Bura, R., Cooper, J., McMahon, R., Schmitt, E., and Vajzovic, A. 2009. Converting Washington Lignocellulosic Rich Urban Waste to Ethanol. http://www.ecy.wa.gov/biblio/0907060.html, verified 02/16/2011.
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