PhD Thesis Defense: Madeline Hoey

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"Strategies for cellulosic biofuel production with technoeconomic analysis: Ex situ ball milling with fermentation, as modeled for cotreatment, to enhance feedstock deconstruction"

Abstract

Advancing the deconstruction of lignocellulosic feedstocks (e.g. corn stover, switchgrass) for conversion into liquid biofuels (e.g. ethanol) if of interest for achieving a net zero/net negative carbon transport sector. A key barrier to achieving economic feasibility of this conversion process is the recalcitrance of lignocellulose, the resistance to deconstruction, which is thought to be linked to the structure of the lignocellulosic matrix. This recalcitrance has been the subject of extensive research and has informed the development of a novel approach known as cotreatment with consolidated bioprocessing (C-CBP), which has been shown to reduce costs compared to conventional conversion paradigms. This thesis explores the use of milling within an ex-situ C-CBP regime as a means of increasing access to lignocellulosic biomass constituent carbohydrates for conversion into ethanol and demonstrating enhanced fractional total carbohydrate solubilization (FTCS). This has resulted in a body of work that saw >90% FTCS in short-duration ball milling, as well as new insights as to the physical and chemical changes seen in the feedstock when subjected to either ball or disc milling using analytical characterization techniques. Finally, a technoeconomic analysis describes the economics of a consolidated bioprocessing based biorefinery at various scales, with comparison to a conventional processing paradigm, and  incorporation of feedstock cost which varies with scale. These results provide further insight into the feasibility of small-scale biorefineries, which require lower overall capital investment, as well as the conditions in which C-CBP is successful for enhancing carbohydrate solubilization.

Thesis Committee

• Lee R. Lynd (chair)
• Evert Holwerda
• Erin Mayfield
• Yannick Bomble (National Laboratory of the Rockies)

Contact

For more information, contact Thayer Registrar at thayer.registrar@dartmouth.edu .