Electrochemical synthesis of CO2-methanol utilizing direct air capture, CO2 electrolysis and H2O electrolysis

A life cycle assessment

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This thesis examines the production of an alternative liquid hydrocarbon fuel, namely CO2-methanol, produced utilising DAC, CO2 electrolysis, H2O electrolysis and thermo-catalytic synthesis. The reason for such research lies in a persistent growth in global energy demand, a significant share of which comes from liquid fuels, in the present context of global climate change.
We answer the main research question ‘What is the comparative environmental performance of DAC methanol, natural gas methanol and biomethanol?’ by meeting three research objectives. The first objective provides a two-level analysis of the mass and energy flows within the system and opens the black-box process of the DAC. The second objective leads to undertaking a life cycle assessment of CO2-methanol. Last, the third objective evaluates the suitability of LCA for the environmental assessment of realistic industrial processes.
The results of objective one show that mass and energy balances on the DAC process contain inaccuracies and help to identify unknowns in the remaining parts of the CO2-methanol production. The second objective illustrates that the CO2-methanol performs better than fossil methanol and biomethanol in terms of climate change impact and land use. Additionally, CO2-methanol causes a lower extent of environmental impact on human toxicity (non-carcinogenics) and resource depletion (water) in comparison with biomethanol, however, scores worse on these impact categories when compared with fossil methanol. The environmental performance of CO2-methanol inferior compared to both biomethanol and fossil methanol in terms of freshwater ecotoxicity, human toxicity (carcinogenics) and resource depletion (mineral, fossils, and renewables). Finally, the third objective points to imperfect LCA software available, not sufficient to model realistic industrial processes.