I was reading some random stuff, and I came across serpentization as an exothermic reaction that can liberate hydrogen from water under some circumstances. I think its pretty interesting because Olivine is not rare, and unlike most reactions that produce hydrogen this one is not energy negative or CO2 emitting. There are some examples of it at some hydrothermal vents where the reaction heats up the water and emits a mixture of hydrogen and methane.
https://en.wikipedia.org/wiki/Lost_City_Hydrothermal_Field
Idea is as follows:
I was thinking high pressure water could get pumped into the rock (basically fracking). All the tiny cracks would give surface area for the reaction to occur. The rock would heat up and a bit of hydrogen would be produced, which could both be exploited. According to everything I have read, the reaction will occur at up to about 400C, theoretically hot enough for dry steam. The hydrogen production could be exploited by something like current natural gas wells drilled on the site.
The main problems I can think of are:
1: The reaction may not be fast enough to be practical even if done over a wide area
2: The water would likely remain under pressure since it needs to stick around to react with the rock, making the gas well a very tricky proposition
3: The cracks would be lined with the reaction product, shielding the unreacted mineral from it.
4: Olivine concentration in the rock might need to be unnaturally high to be possible/practical.
5: Hydraulic Fracturing might not be a practical way to get the surface area needed
Despite identifying these problems, I don't know how big they would be, so I will leave it to everyone else to tell me I should be disappointed
