For info on how to attend this videoconference, email matthew.r.kubis.th@dartmouth.edu.

"Informing and enabling high solid loading lignocellulose conversion via consolidated bioprocessing"

Abstract

Efficient deconstruction and conversion of inedible plant biomass, i.e. lignocellulose, is critical to decarbonizing the energy system in order to meet climate stabilization objectives. However, lignocellulose biomass is recalcitrant to deconstruction, and is often augmented by energy- and capital- intensive thermochemical pretreatment. Alternatively, Clostridium thermocellum is a thermophilic anerobe capable of both deconstruction and conversion of lignocellulose without thermochemical pretreatment.

In this thesis, the deconstruction performance of lignocellulose is evaluated at industrially relevant conditions, i.e., solid loadings exceeding 100 g/L in several configurations. This work seeks to inform the deployment of cellulosic ethanol production by furthering our understanding of C.thermocellum mediated deconstruction. In batch fermentations, it was observed that fractional deconstruction declines as solid loadings increase, which prompted diagnostic experiments and the inclusion of a second bacterium, Thermoanaerobacterium thermosaccrhrolyticum, to improve fractional deconstruction. Ultimately, the bioreactors used to characterize this were unsuitable for work above 100 g/L, which necessitated a novel bioreactor system capable of semi-continuous fermentations. To our knowledge, this first-of-its-kind bioreactor will enable lab-scale characterization of lignocellulose deconstruction at high solid loadings not yet reported in literature.

Lastly, a technoeconomic analyses adds another component to the thesis that describes the project economics and relative greenhouse gas (GHG) emissions for a 60-million gallon per year biorefinery. The impact of adopting emerging technologies such as carbon capture and storage (CCS) and biogas upgrading were evaluated in this context. Results indicate there are significant, i.e., up to 5-fold improvement, in net GHG benefits by adopting this approach, while simultaneously also improving project economics.

Thesis Committee

• Lee R. Lynd (Chair)
• Evert K. Holwerda
• Mark S. Laser
• Tom L. Richard
• Daniel L. Sanchez

Contact

For more information, contact Theresa Fuller at theresa.d.fuller@dartmouth.edu.