Tradeoffs in life cycle water use and greenhouse gas emissions of hydrogen production pathways

Abstract

Hydrogen has been promoted as a key component of global decarbonization efforts, with various past studies estimating carbon emissions for several production pathways, but little past work has considered its water resource needs. This life cycle analysis considers hydrogen production on a per-kilogram basis for 11 pathways, fossil and non-fossil. It also includes impacts of treating water to the required quality for hydrogen production. Greenhouse gas emissions results were in a range of −15 to +31 kg CO2e/kg H2 produced. Water consumption varied more widely, from about 7 to 55 kg water/kg H2 for fossil-based pathways and 530 to 3400 kg water/kg H2 for biomass-based pathways. Electrolysis with various renewable electricity scenarios were also modeled. Overall, there are challenging tradeoffs to be navigated to achieve a low carbon and water footprint in hydrogen economy.