Biomethane Splitting: The Hindered Carbon Removal Potential of Biohydrogen

Biomethane splitting for hydrogen and solid carbon production is an emerging carbon removal technology. It sequesters biogenic CO2 from biomass into solid carbon, enabling negative GHG emissions. Reported GHG emissions vary depending on the accounting framework used. This is the first study to systematically assess MS emissions across the EU Renewable Energy Directive (Red III), the UK Low Carbon Hydrogen Standard, and ISO LCA, addressing the implications of the inclusion and exclusion of biogenic CO2 and carbon credits. GHG emissions are 2.11, −7.41, and 5.32 kgCO2/kgH2, respectively. Red III underestimates the removal potential by excluding both biogenic CO2 and carbon credits. LCA including biogenic CO2 results vary based on biomethane origin, creating an unfavorable scenario for biowaste biomethane. The UK standard offers the most balanced approach, recognizing credits for the solid carbon sequestration.