Only 20%?
I suppose we're not quick enough to capture anything more decent. Well, that's it for lightning, I suppose the human thing is out, nobody seemed eager to capture human excrement and "air", then the sex thing has not really led to any great ideas.
Then there is the thing with the cows and sheep, but I suppose that's just to capture the harmful gases.
So, we're back to solar panels, wind power, fuel cells, and possibly alternative fuels, and on a smaller scale Stirling engines.
Ever wondered if there is not a liquid composition that will be better suited to solar panels, to up the efficiency rating?