Evaluation of the Environmental Impacts of Clean Hydrogen Production and CO2 Utilization from Carbon Capture and Direct Air Capture for Sustainable Chemical Synthesis

The transition to low-carbon industrial processes requires an understanding of the environmental trade-offs associated with emerging chemical conversion technologies. Life cycle assessment (LCA) provides a framework for evaluating these processes against decarbonization goals. This dissertation applies LCA to assess the impacts of methanol production, formic acid synthesis, and hydrogen production, incorporating both carbon capture (CC) and direct air capture (DAC), focused on greenhouse gas emissions. The first chapter establishes an LCA for DAC-based methanol production, showing that wind- and hydro-powered DAC lead to the most net-negative emissions of all energy sources, reaching as low as -2.53 kg CO2 eq per kg methanol. The findings highlight that DAC’s energy source determines the feasibility of CO2-derived methanol. The second chapter applies multi-objective optimization to balance competing stakeholder environmental and economic priorities relative to an LCA study. In the illustrative example, the DAC-to-methanol system is optimized between profit margin of methanol sale and climate change impacts, with the model predicting that the best business strategy is a mix of photovoltaic and wind energy cases. The third chapter examines formic acid synthesis from DAC-derived CO2 regenerated with waste heat. Results show up to a 110% global warming potential (GWP) reduction compared to fossil-based routes, but economic challenges remain, with electricity costs and CO2capture efficiency as key factors. The fourth chapter evaluates the environmental impacts of hydrogen production via gas switching reforming (GSR), a natural gas reforming process that integrates CO2 capture. The LCA results showed that compared to steam methane reforming (SMR), GSR reduces CO2 emissions by 73% and requires 94% less energy than proton exchange membrane (PEM)electrolysis. The final chapter assesses the environmental impacts of various hydrogen production routes for methanol production, showing that integrating renewable electrolysis-based hydrogen lowers emissions by 89% compared to steam methane reforming with CC, while methanol from GSR hydrogen reduces emissions by 30%.Together, these chapters provide a comprehensive assessment of decarbonization technologies, highlighting the interconnected roles of hydrogen production, DAC, carbon utilization, and synthetic fuel synthesis. This research quantifies key trade-offs, guiding the development of sustainable chemical conversion technologies to support climate change mitigation.