Climate-optimal use of green hydrogen

Green hydrogen is projected to play a key role in achieving net-zero emissions, with applications across various sectors. While hydrogen applications have been assessed on costs, competitiveness and feasibility, it is unclear which applications are most favourable for the climate. Here, we use prospective life cycle assessment to compare the greenhouse gas emissions of green hydrogen use in various applications with: (i) their fossil counterparts, and (ii) low-emission alternatives for these applications, which are other mitigation technologies that provide the same service. Specifically, we look at methanol, ammonia, steel, aviation fuel, passenger cars, long-term grid balancing, and domestic and industrial heat production for the year 2030. We demonstrate that green hydrogen production, transport and application leads to emissions savings compared to their fossil counterparts, but emissions are similar or higher than those of the low-emission alternatives. Only with very low hydrogen production emissions and without transport do the green hydrogen-based applications result in net emissions savings compared to the low-emission alternatives for: ammonia, steel, long-term grid balancing, and industrial and domestic heat. We conclude that for green hydrogen to fulfil its anticipated role in the net-zero transition, emission reductions are needed across the supply chain, as well as a prioritisation of hydrogen use in different applications that accounts for and optimises climate benefits.