Headline: Life cycle assessment of hydrogen production by thermal cracking of methane based on liquid-metal technology

Thermal cracking of methane into carbon and hydrogen is considered as potential hydrogen production technology without direct CO2-emissions. In this work, a novel methane-cracking process based on a liquid-metal technology is analyzed using life cycle assessment to evaluate the process' environmental impacts. Based on lab-scale experimental data, the novel methane-cracking process is benchmarked against the existing hydrogen production routes: steam reforming and water electrolysis. We consider the following environmental impact categories: global warming, fossil depletion, metal depletion, and particulate matter formation. According to our analysis, the methane-cracking process can reduce the global warming impact by up to 64% compared to steam reforming. However, the fossil depletion impact is higher for the methane-cracking process due to the higher methane input. The fossil depletion impact can be reduced by utilizing the energy of co-produced carbon to increase process efficiency at the expense of additional CO2-emissions. Methane supply to the process and electricity demand for H2-separation were identified as crucial parameters for the process’ environmental impacts. Thus, we perform parameter studies on alternatives for supply of methane and electricity to identify locations where lowest environmental impacts can be achieved.