Environmental performance of non‑thermal plasma methane splitting across European hydrogen pathways: a prospective LCA

Methane splitting is emerging as a promising technology for the coproduction of hydrogen and solid carbon. This study presents the first prospective life cycle assessment of non-thermal plasma methane splitting (NTP MS), benchmarking its environmental performance against conventional and low-emission pathways for hydrogen and carbon production in Norway, Germany, Spain, and France. Life cycle inventories for NTP MS are developed using process simulations based on experimental data. Results show that NTP MS is an environmentally competitive option compared with water electrolysis, reforming processes with carbon capture and storage, and furnace black production, with greenhouse gas (GHG) emissions ranging from 0.76 to 3.33 kgCO2eq/ kgH2; reaching a reduction of up to 92% relative to conventional steam methane reforming by 2050 in Norway. Germany represents an exception, as the environmental competitiveness of NTP MS depends on the decarbonization of the electricity mix by 2050. Across additional environmental indicators, NTP MS offers a favorable trade-off between GHG reduction and other environmental impacts, benefiting from catalyst-free operation and process multifunctionality. Sensitivity analyses highlight the influence of reactor electricity demand and solid carbon utilization on GHG emissions. Solid carbon use reduces hydrogen GHG emissions, decreasing the hydrogen allocation factor. These findings support NTP MS as a viable low-carbon pathway under specific regional and system conditions and open reflections on the EU low-carbon hydrogen policy approach, which favors solid carbon storage.