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Going underground

A new study's recommendations for carbon capture should be pursued.

The world has no shortage of coal: about a trillion tonnes of the stuff is considered to be recoverable worldwide. It's also cheap: joules from coal cost considerably less than those from natural gas. But coal has a deservedly bad reputation for carbon emissions, which are greater per kilowatt-hour than for any other major electricity source.

The United States has a quarter of the world's coal, and half of its electricity is coal-generated. But power companies are finding it increasingly difficult to build new coal plants, even with increasing demand. The difficulty is twofold. Environmental lawyers and lobbyists are making the process as lengthy, expensive and unpredictable as possible. And companies are increasingly convinced that carbon regulation is coming to the country, maybe not today, maybe not tomorrow, but soon, and for the rest of our lives. Politicians in the Democratic Party have made clear their intention of penalizing any attempt to cheat future regulations by building large numbers of plants before these regulations take effect.

This confluence of factors contributed to the decision this year by Texas electricity company TXU to back away from its idea to build eleven new coal plants (see page 362). Instead, the company looks set to be bought out by a group of investors who cannily obtained public support for the deal from environmental groups, in part by pledging not to build eight of the eleven plants — a decision they would probably have made anyway. Meanwhile, the idea of banning further construction of coal plants is being promoted by an unprecedented range of people, including NASA's Jim Hansen, members of the Texas legislature, and a United Nations panel chaired by the director of the Missouri Botanical Garden, Peter Raven. The epoch of US coal plants without carbon capture and storage may be coming to an end.

That would be just fine for many people, to whom coal is anathema. There are plenty of alternatives, from renewables to natural gas. The latter is plentiful in the United States and is cleaner-burning. And although the general idea behind carbon capture and sequestration seems reasonable to most experts, it hasn't been tried at the truly colossal scales that would be needed. Pumping gigatonnes of carbon underground is not to be undertaken lightly. Early studies indicate that there is sufficient capacity, but detailed surveys must be made. Questions about leakage and the best ways to monitor the sites must be answered. Full-scale demonstration plants must be built with varying technologies and on different geologies, and they must be carefully monitored and studied.

The MIT report calls for immediate investment in carbon capture and sequestration projects.

This is challenging indeed, but a study by researchers at the Massachusetts Institute of Technology, The Future of Coal, finds that the technology is viable. According to their models, it will be adopted when carbon emissions cost US$30 a tonne. The report calls for immediate investment in carbon capture and sequestration projects, with a total of ten projects worldwide at a cost of about $15 million each per year for ten years.

This figure of $1.5 billion may sound big, but it's tiny when compared to the role of coal in the worldwide energy industry. Despite all the uncertainties and all the other energy options, this proposal should be implemented. If carbon markets and competing technologies eventually lead most countries to abandon coal as an energy source, so much the better. But it is impossible to be sure of such an outcome, and the risks of global change are serious enough for the United States and other countries to be pursuing all low-carbon energy sources with vigour.

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Going underground. Nature 446, 348 (2007).

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