Hydrogen

Most of the current methods of producing hydrogen are based on using fossil fuels, and thus produce CO₂ in the atmosphere, unless the CO₂ produced is also captured. Steam reformation of methane is the most commonly used and is the least expensive. It needs an external heat source, but does not need pure oxygen. Hydrogen can also be made starting with syngas, made from coal, and then using the water gas shift reaction to produce hydrogen. It is also possible to start with biomass and produce syngas from that, but again you end up with CO₂ to capture, and also typically a lot of SO₂ and oxides of nitrogen which are also bad pollutants.

So this all feels like the wrong way to go.

Thankfully there are ways to produce Hydrogen that do not produce CO₂

but we need to make them economically viable

A novel method of producing hydrogen from methane is plasma arc decomposition (PAD) where high temperature decomposition of methane in the absence of air (pyrolysis) produces pure H₂ and solid carbon. This sounds promising, but an attempted commercial operation was abandoned because it was a more expensive way to produce hydrogen than using steam reformation of methane. A form of this process at an even higher temperature can also produce carbon nano-tubes. Given that this requires a large amount of energy and a high temperature, it may become far more feasible if we are using MSTGs to provide the raw heat and electricity.

Another alternative production method is alkaline water electrolysis, using a platinum electrode. This requires the water to purified before starting the process, which takes energy. Amounts of electricity required though are compatible with electricity produced from PV or wind. Other electrolysis processes use polymer electrolyte membranes, or solid oxide electrolyser cells (SOEC). SOEC is a high temperature process and is very efficient. The only problem with SOEC is developing stable materials to cope with the high temperatures involved. However, again this would be plausible if using MSTGs for the heat source.

One form of electrolysis called Carbon-assisted water electrolysis (CAWE) produces CO₂, so that is another method worth avoiding.

We could also use the high temperature sulphur-iodine cycle, which again is far more plausible if using MSTGs as a direct heat source.

Another non CO₂ producing method is photo-catalytic water splitting. In the presence of a catalyst, light can be used to split water into hydrogen and oxygen. However this method is very low efficiency, only about 11% efficient in energy terms.