Abstract
In the context of climate change, most of the actual dihydrogen production is not sustainable with about 96% of the 60 million tons of dihydrogen produced annually generated by reforming of fossil fuels, calling for cleaner methods of dihydrogen production. Here we review dihydrogen production from wastewater with focus on biological methods, electrochemical methods, dihydrogen storage, techno-economic aspects, governance and applications. Methods include fermentation, photolysis, photocatalysis, electrolysis and supercritical water gasification. Applications comprise refining crude oil, ammonia production, the food industry, metal extraction, pharmaceuticals, fuel cells, combustion engines, power generation and energy carrier.