Date of Award

2025

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Chemical Engineering (MS)

Administrative Home Department

Department of Chemical Engineering

Advisor 1

Robert M. Handler

Committee Member 1

David R. Shonnard

Committee Member 2

Kyle B. Griffin

Abstract

The Cool Gas-to-Liquid (Cool GTL) process converts biogas and captured CO2 into renewable hydrocarbon fuels, contributing to GHG emissions reduction in transportation. This report explains a Life Cycle Assessment (LCA) study that was completed to evaluate the environmental impact of different feedstocks, hydrogen sources, and electricity inputs. The analysis considers biogas from food waste, manure, and landfill sources, as well as biogenic, fossil, and direct air capture (DAC) CO2 feedstocks. Results show that biogas pathways provide the greatest GHG reductions, with the best case (food and manure biogas + solar hydrogen + solar electricity) achieving a net-negative GWP of -60.2 g CO2eq/MJ fuel, representing a 171% reduction compared to conventional fossil jet fuel emissions. Biogenic CO2 feedstocks also lead to a 69% reduction in emissions (26.1 g CO2eq/MJ fuel) but require renewable inputs. Fossil CO2 and DAC pathways often yield higher emissions, with the worst DAC scenario reaching 205.8 g CO2eq/MJ fuel, surpassing fossil jet fuel emissions. Findings emphasize the need to prioritize biogas, transition to green hydrogen, and use renewable electricity for sustainability.

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