My augmented society of humans have managed to engineer their power-hungry cyborg components to run on a hydrogen fusion reactor. Whilst they have so far managed to fuel it by drinking lots of water, they would rather a solution which would make their lives more convienient. Would they be able to add either hydrogen (at appropriate pressure) replacing the nitrogen, or even just a couple percent of hydrogen that would stay at ground level for them to breathe?
They don't care about the hydrogen staying over geological time and can replenish it, but would like the planet to be at least inhabitable if their technology stopped maintaining it. (It has an ecosystem like Earth)
They have handwavium nanotech clouds that would help with fire supression, but would like to avoid any situations where a spark would blow up the planet anyway
So, is this possible?