"Hydrogen, the most common element in the universe, has a lot of promise for the energy transition: it can power cars, provide electricity to buildings, and be used to help decarbonize tough industries like manufacturing and construction. The problem with hydrogen is that it needs to be separated from other elements, which in and of itself takes a lot of energy. Hydrogen can be separated from oxygen in water via electrolysis to create what’s known as green hydrogen—an option free from any greenhouse gas emissions, but one that’s pretty expensive. It can also be harvested from fossil fuels like coal and gas, to create what’s known as gray hydrogen. This is a little cheaper than green hydrogen, but emits quite a lot of CO2 during the hydrogen extraction process."
Source: https://gizmodo.com/big-oil-s-new-clean-fuel-is-dirtier-than-they-say-1847474392
