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MS Thesis Defense: Zachary Losordo

Thursday, February 27, 2020, 9:00–11:00am

Rm 105, Cummings Hall

“Cost Competitive Second-Generation Ethanol Production from Hemicellulose in a Brazilian Sugarcane Biorefinery”

New technologies are needed to meet the growing global demand for transportation fuel while mitigating the risks of climate change. Second generation (2G) ethanol, which is produced from inedible lignocellulosic plant material, is a promising technology that provides greenhouse gas reductions compared to conventional fuels and avoids direct competition with food production. Despite a significant technology development effort to realize these benefits, 2G ethanol commercialization was unsuccessful. Lignocellulosic carbohydrate, in particular, the six-carbon (C6) cellulose fraction is highly recalcitrant to conversion requiring multiple unit operations and high cost inputs which renders the process uneconomical. An alternate strategy would produce 2G ethanol selectively from the five carbon sugars in the hemicellulose rather than from the six carbon sugars found in cellulose. Although the five carbon sugars represent a smaller fraction of the available carbohydrate, they can be more readily extracted and converted. Sugarcane mills would be an ideal host for a C5 process due to pre-existing infrastructure and readily available 2G feedstock. This analysis finds that in this integrated context, a C5 strategy could cost effectively increase ethanol yield at first generation (1G) sugarcane biorefineries in Brazil. Process modeling analysis predicts that C5 extraction strategies can permit increases in total sugar recovery of 11% to 20% on sugarcane compared to traditional extraction. Co-fermenting the C5 sugars with cane juice and molasses can be accomplished using bioengineered yeast in the pre-existing fermenters which is an integration enabled by recent biotechnology advances. Due to close integration with the 1G host plant, these projects achieve a minimum ethanol selling price (MESP) of $0.17/L to $0.29/L at a 10% return, which is lower than the reported MESP for other 2G projects and is cost competitive with 1G ethanol and gasoline.

Thesis Committee

For more information, contact Daryl Laware at daryl.a.laware@dartmouth.edu.