This site uses cookies. By continuing to use this site you agree to our use of cookies. To find out more, see our Privacy and Cookies policy.
Skip to the content

[IOP] A community website from IOP Publishing

Tag Archives: underground coal combustion

Hydrogen futures: coal-fired fuel cells?

There has been a proposal from B9 Coal to use AFC Energy’s alkaline fuel cell technology with hydrogen produced from burning coal in situ underground in a 500 MW in Northumberland. Underground coal gasification (UCG) produces syngas, which is then passed through a clean-up process, resulting in separate streams of hydrogen and carbon dioxide. Upwards of 90% of the CO2 can then, it is claimed, be captured as a by-product at no extra cost. The pure H2 is passed through the fuel cell, converting to electricity at 60% efficiency at a projected cost as low as 4p per kWh.

UCG does avoid mining, with all its costs and risks. But UCG has some problems, as was found in early projects in the US and Russia. There have been accidental fires in coal seams underground which have been hard to control: one in Columbia County, Pensylvania, started 1962 and is still burning. The official response is that though relatively shallow coal seams can burn if an air flowpath exists, UCG cannot burn out of control. Combustion requires a source of oxygen, and this can in theory be controlled, so there is allegedly no possibility of oxygen reaching the coal which, for UCG, needs to be at a depth of 500 to 2000 metres and lying beneath impermeable rock strata. But even if that is true in practice, in situ coal does not burn cleanly or evenly – you get partial oxidation and a range of pollutants, including tars, phenols, ammonia. So there are clean-up costs.

More on UCG at:

Also the efficiency of making hydrogen from coal is usually said to be only about 65%. So with fuel-cell efficiency at best 60%, that gives and overall efficiency of under 40%, which may be low compared with direct use of mined coal in Integrated Gasification Combined Cycle plants, even with Carbon Capture and Storage (CCS).

However, why bother with complex and expensive IGCC plants? Why not just use the hydrogen direct as a heating fuel, sent to users via the gas main (piping gas is cheaper than power distribution by electricity grid). Or, if you really do need electricity, then use the hydrogen in homes in a CHP fuel cell – so recycling some of the otherwise wasted heat and raising the efficiency to maybe 70%.

Biomass as an alternative

Then again why use coal for the hydrogen source? What’s wrong with biomass? That’s more or less carbon neutral if it’s replaced by regrowing. There is a range of ways for producing hydrogen, methane or syngas from biomass including anaerobic digestion, pyrolysis, and gasification. In one approach, biomass is gasified to make carbon monoxide, and then using the standard shift reaction (CO+H2O = CO2 + H2) this is converted to hydrogen, and while the CO2 is captured and stored, so making it overall carbon negative.


There are land-use and biodiversity limits to how much we want to rely on biomass, but, intriguingly, the Sahara Forest Project includes the idea of growing algae in seawater-fed desert greenhouses, and there is plenty of desert and sea water.

Of course, there is also quite a lot of coal and in situ coal gasification may open up a new approach to using old part-worked coal seams. But if we want to avoid both coal and biomass, then what’s wrong with getting hydrogen using solar-, wind-, wave- or tidal-derived electricity, via electrolysis of water, or even by direct high-temperature dissociation of water via focused solar?


The latter is still relatively inefficient (1–2%) and both approaches are still expensive compared with conventional approaches to hydrogen production. However, the technology is improving. One 2009 study suggested that, while hydrogen produced via steam reforming of natural gas costs around $6–8 per kilogram of hydrogen, H2 from solar (via electrolysis) costs $10–12 per kg, from wind (via electrolysis) $8–10 per kg, and from solar via thermo-chemical cycles (assuming the technology works on a large scale) $7.50–9.50 per kg.

So we are getting there. For example, a 2002 study noted that PV costs of ˜$300/kWpk were needed to get H2 cost of $7-8/MMBtu via electrolysis, comparable with the cost of hydrogen production from coal, which, with current gasification technology, is $6.50-7.00 per MMBtu, or just over $8.00/MMBtu with CCS.

But some PV modules are now claimed to cost below 76 cents/Wpk, and it’s claimed that in some locations PV can deliver energy at costs below that from new nuclear plants, as can wind power. See and

However, electrolysis is only about 60% efficient, unless the waste heat can be recovered, and there is still a way to go before it, and other novel renewable powered or biomass-fed approaches, can rival conventional steam reformation of fossil fuels for hydrogen production on a large scale. So, if we want hydrogen, maybe we could go for coal UCG/ CCS just as an interim step?

Some of the above is based on discussions in the Energy Group.

Posted in Renew your energy | Tagged , , | Leave a comment | Permalink
View all posts by this author  | View this author's profile