Date of Award

8-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Pankaj Lal

Committee Member

Melissa Harclerode

Committee Member

Renata Blumberg

Abstract

Under provisions of the Energy Independence and Security Act and the Renewable Fuel Standard, production of cellulosic ethanol is mandated to increase. Corn dominates the first generation ethanol industry in the United States. Already a high-demand crop, when subject to agricultural intensification, the carbon-neutrality potential associated with biofuels, and other environmental implications, fall into question. Sugarcane bagasse, a lignocellulosic byproduct of sugarcane manufacturing with limited economic value, and switchgrass (Panicum virgatum), a native, perennial, high-yield crop, are alternative resources that might used to produce ethanol. Life cycle assessment of second generation feedstocks has focused exhaustively on global warming potential with minimal consideration to broader impact categories. In this study, traditional dry-milled corn ethanol is compared to sugarcane bagasse and switchgrass that is derived using dilute phosphoric steam acid pretreatment and simultaneous saccharifcation and cofermentation. Modeled over ten-year scales, using E85 and E15 fuel blends scenarios, switchgrass and sugarcane bagasse fuel blends had greater global warming potential (kg CO2-eq) compared to corn at equal blend ratios. As the ethanol ratio increased, the hotspot would transition from fossil fuel production and emissions to fermentation driven by increases in enzymes, chemicals, and electricity. Water consumption, stratospheric ozone depletion, and marine eutrophication were reduced for switchgrass compared to corn due to lesser agricultural demands predominantly associated with upstream processes. Further research should include reduction of enzymes while maintaining ethanol yield and characterization of stillage.

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