To produce green hydrogen, an electrolyser splits water (H2O) into hydrogen (H2) and oxygen (O2). The electrolyser is powered solely by renewable electricity, from wind energy for example. As such, no CO2 is released with the production of green hydrogen.
Besides green hydrogen, there is also grey and blue hydrogen. Grey hydrogen is made from natural gas. CO2 is released during that process. With blue hydrogen, the hydrogen source is still natural gas. Only, up to 90% of the CO2 emissions are captured and stored underground or used in greenhouse horticulture. Green hydrogen has the same characteristics as grey or blue hydrogen. However, green hydrogen is the most sustainable version.