Environmental performance of hydrogen-based synthetic methane, diesel, and petrol: A prospective life cycle assessment

This study provides a harmonised prospective life cycle assessment (LCA) of hydrogen-based synthetic methane, diesel, and petrol produced via Power-to-Fuel (PtF) pathways under different electricity supply scenarios. The analysis integrates key process steps including water electrolysis, direct air capture (DAC), reverse water–gas shift (RWGS), and fuel synthesis via Sabatier and Fischer–Tropsch processes within a consistent cradle-to-gate system boundary. Results show that electricity supply is the dominant driver of environmental performance, with water electrolysis contributing more than 80% of total impacts across most scenarios. Among the assessed fuels, synthetic methane exhibits the lowest overall environmental burden compared to diesel and petrol. Environmental impacts vary significantly with the electricity mix, revealing trade-offs between climate change mitigation and increased impacts in categories such as ionising radiation and resource use. The findings demonstrate that differences between fuel pathways diminish under future low-carbon electricity systems, indicating a convergence in environmental performance. The study contributes to the literature by providing a harmonised multi-impact comparison of PtF pathways, with results reported as overall environmental impacts further disaggregated into LCA impact categories.