Sustainable Hydrogen Production with Negative Carbon Emission Through Thermochemical Conversion of Biogas/Biomethane

Biogas (primarily biomethane), as a carbon-neutral renewable energy source, holds great potential to replace fossil fuels for sustainable hydrogen production. Conventional biogas reforming systems adopt strategies similar to industrial natural gas reforming, posing challenges such as high temperatures, high energy consumption, and high system complexity. In this study, we propose a novel multi-product sequential separation-enhanced reforming method for biogas-derived hydrogen production, which achieves high H2 yield and CO2 capture under mid-temperature conditions. The effects of reaction temperature, steam-to-methane ratio, and CO2/CH4 molar ratio on key performance metrics including biomethane conversion and hydrogen production are investigated. At a moderate reforming temperature of 425 ◦C and pressure of 0.1 MPa, the conversion rate of CH4 in biogas reaches 97.1%, the high-purity hydrogen production attains 2.15 mol-H2/mol-feed, and the hydrogen yield is 90.1%. Additionally, the first-law energy conversion efficiency from biogas to hydrogen reaches 65.6%, which is 11 percentage points higher than that of conventional biogas reforming methods. The yield of captured CO2 reaches 1.88 kg-CO2/m3 -feed, effectively achieving near-complete recovery of green CO2 from biogas. The mild reaction conditions allow for a flexible integration with industrial waste heat or a wide selection of other renewable energy sources (e.g., solar heat), facilitating distributed and carbonnegative hydrogen production.