Climate impact of bioH2 production from biogas using CO2 mineralization for carbon capture and storage

Abstract: Carbon dioxide (CO2) concentrations in the atmosphere are increasing and are now higher than they have ever been, mostly because of CO2 released from burning fossil fuels for energy. Global energy demand will continue to rise in the future, resulting in increased carbon emissions. Hydrogen (H2) could potentially decarbonize energy systems and replace fossil fuels. Climate impact from H2 production varies but can be considered carbon-neutral if production is replaced with biomethane as feedstock instead of natural gas. Then it is referred to as biogenic hydrogen (bioH2). If carbon capture and storage (CCS) is applied to bioH2 production, it can result in negative emissions. Carbon mineralization is a CCS method where CO2 is injected into underground basaltic reservoirs to rapidly convert into carbonate minerals, providing permanent CO2 storage. This study used a life cycle assessment (LCA) method to identify greenhouse gas (GHG) emissions and climate impact from bioH2 production coupled with carbon storage mineralization. The chosen climate metric for the study is the global warming potential (GWP). This study used a hypothetical biogas plant where the bioH2 is produced with biomethane as feedstock via the steam methane reforming (SMR) method. The hypothetical carbon mineralization storage site is located right outside of Uppsala where the CO2 emissions are injected and long-term stored each day. The results show that implementing CO2 mineralization to bioH2 production reduces climate impact and leads to carbon removal. The climate impact can be reduced or increased depending on different factors such as electricity source, CH4 leakage rate from biogas, CO2 capture efficiency from bioH2 production, the scope of CO2 capture, and different GWP time horizon. The biggest improvement is when the bioH2 production is operated with renewable energy and the CO2 capture is increased both in scope and efficiency. Mineralization of CO2 emissions from bioH2 production results in significantly reduced climate impact. By integrating the two technologies, it is possible to contribute, to meet the Paris Agreement targets of keeping global warming below 1.5°C to 2°C.