Comparative Greenhouse Gas Impact Assessment of Well-to-Use Hydrogen and Other Alternative Pathways Across 11 Use Cases

Investments in “clean” hydrogen as an alternative to fossil fuels are driven by anticipated climate benefits. However, most climate impact assessments of hydrogen pathways overlook or underestimate important climate-warming emissions (i.e., hydrogen, methane) and impacts over time. Moreover, hydrogen is often evaluated against conventional fossil fuels without considering alternative decarbonization options, which limits the ability to inform decision-making effectively. This study evaluates the greenhouse gas emissions mitigation potential of 31 well-to-use hydrogen pathways (renewable- and grid-based electrolytic hydrogen and fossil fuel-based hydrogen with carbon capture and sequestration [CCS]) and 14 other alternative pathways (direct electrification, electro-fuels, and CCS) to replace conventional fossil fuels for eleven use cases across various economic sectors. We aim to quantify the effect of hydrogen and methane emissions on the climate benefits of decarbonization pathways and provide guidance on where to deploy hydrogen for maximum climate benefits. Preliminary results show that, across all use cases, hydrogen and methane emissions can considerably reduce the near-term climate benefits of a decarbonization pathway, with an average of a 3% and 12% reduction for every 1% of hydrogen and methane emitted, respectively. Renewable electricity-based pathways (direct electrification, hydrogen, and electro-fuels) consistently offer greater climate benefits than pathways that involve fossil fuel and CCS, but their deployment should consider the efficiency of utilizing renewable electricity. For use cases where direct electrification is available (i.e., light-duty vehicles, buses, trucks, and home heating), it is the most efficient option to reduce climate-warming emissions. Hydrogen and electro-fuels can achieve comparable benefits but demand around 1.4-7 times the renewable electricity capacity. Therefore, they should be reserved for use cases where electrification is limited (i.e., ship, aircraft, industrial heat, power) and where hydrogen serves as a feedstock (i.e., fertilizer, steel, refinery). In these cases, additional renewable capacity buildout is required to avoid diverting resources from other essential decarbonization strategies and inadvertently increasing system level emissions.