Greenhouse gas emissions implications of hydrogen fuel cell technology for passenger trains

The transportation sector contributes over a quarter of the greenhouse gas emissions in Canada. Rail decarbonization remains challenging where electrification is not feasible. Hydrogen fuel cell trains may offer an opportunity to mitigate carbon emissions in these areas. Their environmental impacts depend on hydrogen leakage, fuel distribution pathways, and the carbon intensity of hydrogen production. This study quantifies the life cycle greenhouse gas emissions of a regional hydrogen train compared with a diesel train using primary operational data from a pilot project in Quebec, complemented by secondary data. A well-to-wheel model evaluates scenarios of hydrogen leakage and fuel distribution pathways considering short- and long-term climate impacts. Uncertainty is quantified through Monte Carlo simulations, and critical thresholds are identified through environmental break-even analysis. The hydrogen train emits 3 g carbon dioxide equivalent (CO 2 -eq) per passenger kilometre (PKM) compared to 26 g CO 2 -eq per PKM for the diesel train at full passenger loads and optimal conditions using a 100-year global warming potential (GWP). High hydrogen leakage reduces the climate benefits by approximately 26% using a 20-year GWP with diesel trucks transporting fuel. Low leakage scenarios achieve 83–86% emission reductions using fuel cell trucks and pipelines over a 100-year horizon. The sensitivity analysis identifies key parameters, including the carbon intensity of electricity used for hydrogen electrolysis and the fuel consumption rate. A hydrogen emission rate of 6.6% or higher eliminates the climate benefit for diesel truck delivered hydrogen. The break-even electricity emission factor ranges from 0.14 to 0.26 kg CO 2 -eq per kWh across distribution pathways. These findings provide quantitative thresholds to guide hydrogen deployment in rail transportation and highlight key data gaps in life cycle inventories, supporting leakage mitigation and low-carbon electricity supply as priorities for decision makers.