Short term reduction achievable within 5 years
Most domestic and industrial heating systems burn methane, obtained from the North Sea gas fields. The CO2 produced is vented into the air, from millions of homes & factories, contributing 50% to our current total emissions. Pilot schemes are currently being evaluated, using blended gas: a mixture of methane and 20% hydrogen. This requires no alteration to the existing heating or distribution systems and no new technology. If introduced nationally, this would significantly reduce our CO2 emissions. Hydrogen is made by industrially by the steam reforming of methane and other hydrocarbons. The final products being hydrogen and carbon dioxide. The CO2 is easily removed from the gas stream. It would be possible but completely uneconomic, to remove CO2 from individual domestic or industrial boilers. Siting the hydrogen production process close to the point where the methane comes ashore and taking advantage of the economy of scale, the CO2 removed could be piped back into the depleted gas fields, effectively removing 20% of all existing emissions.
Long term reduction achievable within 15 years
Blended gas still contains hydrocarbon, the aim should be to replace this with 100% hydrogen and so achieve zero CO2 emissions. The existing National Grid distribution network, has 7,660 km of modern large diameter pipework, together with 618 above ground installations. In addition there are hundreds of thousands of km of smaller diameter, urban pipework, feeding into our homes, factories and hospitals. This will all need modification to carry pure hydrogen but is entirely achievable. This is almost the reverse of what was done 50 years ago, when town gas was replaced with methane. Town gas being made from coal, contained 50% hydrogen.
Generating the hydrogen.
This will be done by electrolysing alkaline sea water, using a recently developed nickel electrode, the products being hydrogen and oxygen. The electrical energy coming from wind turbines. The coast being the ideal setting. The new electrolysis plants being built alongside the steam reforming plants which they will eventually replace. The existing pipe work and electrical plant all being reused.
Advantage of using seawater
Relatively pure water is needed for electrolysis, which makes the process expensive. Acid or alkali being added to make the water conduct. Sea water containing salt (sodium chloride), would normally produce chlorine on electrolysis, as well as hydrogen, in equal amounts. It would be impossible to use the chlorine produced on this scale and it would be uneconomic to dispose of it. The newly developed nickel electrode, prevents discharge of the chloride ions, oxygen gas forming instead. This can easily be used industrially or vented harmlessly into the air. Excess hydrogen can be converted to ammonia and exported as a liquid, as already happens, in tanker ships. The ammonia being converted back into hydrogen as required.