King coal is ready for a British comeback in a form that sounds more like medieval hellfire than an energy source for the 21st century. But could it be green? The stakes are high – not least because the company behind the plan has captured the high ground in environmental marketing by calling itself Clean Coal Limited.
The idea is this. Forget about mining coal, and instead burn entire coal seams in situ underground, then tap the gases that the fires give off to put in gas turbines and generate electricity. Unknown to most residents, the company has already obtained licences from the UK Coal Authority to do this at five sites round Britain's coast.
Seismic surveys could be finished within two years and the company says the first commercial scheme could be in operation by 2014. The combined coal reserves for the five trial sites alone are enough to supply Britain with coal for more than a decade.
Clean Coal is a small start-up company of engineers, geologists and venture capitalists, that has big plans for selling its expertise round the world. Last week, it unveiled plans to burn coal within 500m off the shore of the north Norfolk area of outstanding natural beauty.
But its chief executive, Catherine Bond, told the Guardian that the first project is likely to be in Swansea Bay "because we know the geology best". The other three sites are off Grimsby, Sunderland, and under the Solway Firth in Scotland.
Coal "gasification" is an old idea. Until half a century ago, Britain ran on "coal gas" manufactured at local gas works. What is new is cutting out the coal mining stage and doing the gasification underground.
In principle it is simple. You sink a borehole to the coal seam and insert a firelighter and oxygen to keep the fire going. The fire generates carbon dioxide, methane and hydrogen. You sink another borehole to extract the gases. There are technical issues. But trials on coalfields in Queensland, Australia suggest the technology may be ready to go.
And Bond says she has assembled "the top people in the northern hemisphere. Only the Queensland people are ahead of us. They are proving the technology."
But how green is it? Gasification has one advantage over burning coal directly. By converting coal to methane, you reduce the carbon dioxide emissions at the power station by more than half.
The problem is that methane is not the only gas to emerge from underground. While the engineering trick is to manage the fires to maximise methane production, there will inevitably be a lot of CO2 produced by the fires as well.
So what do you do with it? Bond says they plan to capture the CO2 at the wellhead and find a safe home for it – carbon capture and storage (CCS). "Because of our name, we can't do any project without a CCS solution," she says. But the company's website simply says its technology will "allow" carbon capture to be included at the well head. So how firm is the commitment?
The aim is to pour as much of the CO2 as possible right back into the underground cavity created by burning the coal seam. At the depth planned for burning, below 700m, the gas will form a gel and take up less space. Even so, Bond says: "There is only room for about 30% of the CO2."
The remaining 70% will have to find another home. "We are talking to people about what the options are, but it will be difficult," she says. "We want to be clean. But we may not be capturing all the CO2 from day one." Bond agrees that CCS "is not done on a commercial basis anywhere in the world."
And, as I have reported here before, most people believe any kind of commercial system for CO2 burial is at least a decade away. "I am not going to say a CCS solution is simple and straightforward," says Bond. "But when we do it, we may well be the first."
The problem is that underground coal gasification is emerging as another technology aimed at keeping alive the vast and climatically dangerous coal industry on a prospectus of highly uncertain promises about possible future carbon capture and storage.
The stakes are immensely high. According to the International Energy Agency, unexploitable coal reserves deep in the Earth amount to around 5 trillion tonnes, five times the reserves currently recoverable with mining. Underground coal gasification could make much of that exploitable.
So is this clean coal or greenwash? Bond and her colleagues sound serious. But even if they are true to their word, it is far from clear how soon CCS can be used to bury their unwanted subterranean gases. One thing is for sure. The name of the company ensures its track record will be viewed with specially close scrutiny.
Guardian 05 March 2010
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