Greenest Hydrogen is White Hydrogen!

Hydrogen comes in a rainbow of varieties. "Grey" hydrogen comes from reforming methane; "grey" can become "blue" if the CO (carbon monoxide) byproduct of grey is stored underground; "green" is produced from water by carbon-free renewable electricity.

Hydrogen formed from solar powered electricity is "yellow"; "red" is made chemically from biowaste; "black" by coking coal using steam; "pink" by nuclear powered electrolysis; and "turquoise" from methane, leaving only solid carbon, using renewables and - probably - magic!

You can learn all this by reading THIS ARTICLE which was based on this LONG ARTICLE 

But best of all is "white" hydrogen - hydrogen produced from the earth without any processing. This was thought not to exist - mainly because no one was looking for it! Petroleum companies did not analyse for hydrogen when they tested gas produced. And hydrogen is not found in the sorts of rocks petroleum companies were drilling.

Eventually it was realised that hydrogen was coming out of the earth. And as people began to look for it the more was found. Where does it come from? - That is still being worked on. The following diagram tells all (as far as we know).

There is a lot of interest in hydrogen exploration. Will it save civilization? Watch this space!