> There is already a great deal of equipment for manipulating hydrogen on an industrial scale
If by "a great deal" you mean "a fraction of one percent of what is required". No, the issue I'm raising is not well solved. Currently hydrogen is used shortly after it's produced, typically for chemical manufacturing or oil refining. It's not being stored for long periods of time, nor is it being transported in anything close to the amount of natural gas.
> The great majority of methane storage is underground as compressed gas, not cryogenic. Underground storage is cheap; the capacity in the US is a good fraction of the annual consumption of natural gas here. It is this long-proven technology I am referring to, which should have been clear from what I wrote earlier.
That's assuming these underground storage will work with a substance that has greater permeability. And storage is only half the problem, it's also a matter of the infrastructure used to transport gas to the end user. Simply pumping hydrogen through the same pipelines as natural gas isn't as easy as it sounds. Hydrogen has greater permeability and turns metals into hydrides at pressure. Hydrogen pipelines need to be much more corrosion resistant.
To put this in comparison, the US has 2 million miles of natural gas pipelines [1]. It only has 900 miles of hydrogen gas pipelines [2]. Most hydrogen is produced near areas of demand, and is not transported for long distances or stored for long periods of time. There's research into carbon-fiber pipelines that could better resist corrosion, but this is not a mature level of technology. It's more feasible to pipe methane, and then use steam reforming on-site.
> The density of hydrogen gas at STP is less than 0.1 kg/m^3. Divide to get 7.0e11 m^3.
Volume doesn't matter, I converted the volume of methane produced to mass.
> Globally, 6% of natural gas production is used to make hydrogen. I wasn't talking about hydrogen production by electrolysis; I was talking about total hydrogen production, to show that hydrogen is a material that global industry already has vast experience with.
Excellent point, total hydrogen production is 70 million tons with most of it produced through steam reforming (which produces carbon dioxide). Electrolysis only accounts for 4% of hydrogen production: https://en.wikipedia.org/wiki/Hydrogen_production#Methods_of....
The fact that 6% of natural gas production is used to make hydrogen doesn't mean that our hydrogen production equals 6% of our natural gas production. Most of the natural gas used in steam reforming is used to produce heat. And methane is 75% carbon by mass.
To recap, we have 3 orders of magnitude less hydrogen production and hydrogen transport infrastructure. Even less if you only count hydrogen produced through electrolysis. This is in no way "a great deal of equipment for manipulating hydrogen at scale".
1. https://www.ncsl.org/research/energy/state-gas-pipelines.asp...
2. https://en.wikipedia.org/wiki/Hydrogen_pipeline_transport