The global potential for converting renewable electricity to negative-CO2-emissions hydrogen

The IPCC has assigned a critical role to negative-CO2-emissions energy in meeting energy and climate goals by the end of the century, with biomass energy plus carbon capture and storage (BECCS) prominently featured. We estimate that methods of combining saline water electrolysis with mineral weathering powered by any source of non-fossil fuel-derived electricity could, on average, increase energy generation and CO2 removal by >50 times relative to BECCS, at equivalent or lower cost. This electrogeochemistry avoids the need to produce and store concentrated CO2, instead converting and sequestering CO2 as already abundant, long-lived forms of ocean alkalinity. Such energy systems could also greatly reduce land and freshwater impacts relative to BECCS, and could also be integrated into conventional energy production to reduce its carbon footprint. Further research is needed to better understand the full range and capacity of the world’s negative-emissions options.