Green Hydrogen

Green hydrogen is produced by splitting water in an electrolyzer powered by renewable electricity, so its production carries no fossil carbon, unlike grey hydrogen from steam-methane reforming or blue hydrogen that adds carbon capture. In shipping it is both a candidate fuel for combustion engines and fuel cells and the feedstock for synthesizing e-ammonia and e-methanol. Its drawbacks are low volumetric energy density, cryogenic or high-pressure storage, and a cost still set by renewable-power and electrolyzer prices.