Hydro­gen (H₂) is a color­less, odor­less substance that occurs in all living organ­isms, predom­i­nantly in chem­i­cal compounds like water. It is an energy source that is play­ing an impor­tant role in the energy tran­si­tion. Unlike elec­tric­ity, it can be stored easily and does not emit green­house gases when combusted. Green hydro­gen is produced by water elec­trol­y­sis using elec­tric­ity from renew­able sources in a CO₂-neutral way. It can replace fossil fuels and be used as an indus­trial raw material.