Except for Joe Biden, who delivers a thorough shaking to anyone who questions him on the subject, the candidates in the presidential race have all been tripping over each other to support "clean coal." What they mean here is that they favor research into ways to capture and sequester the CO2 emitted from coal-fired plants. Many environmentalists think that this is all just a cover for continuing to build dirty coal plants, and have started a small Internet cottage industry devoted to debunking "clean coal" claims and explaining why carbon capture and sequestration will be too complicated and expensive to ever be practical.

So just how much would carbon capture and sequestration cost? A new McKinsey report on the economics of carbon sequestration in Europe suggests that by 2030, when the technology has presumably matured, it will cost somewhere between 30 and 45 euros per ton of CO2 captured. These numbers are speculative and—given large upfront costs—particularly sensitive to the cost of capital. But they're also in line with what McKinsey estimates that the cost of emitting CO2 will be in Europe by 2030 under various emissions regimes, which means that, if predictions hold—and if governments are wiling to invest in demonstration projects to get sequestration running—then carbon capture and storage could be economically feasible in less than fifteen years.

But it's not enough to ask whether carbon capture could be done. A better question is whether it's the best investment for governments to be making. How does carbon sequestration for coal plants compare, in terms of the cost of keeping one ton of CO2 from escaping into the atmosphere, with other methods of reducing carbon emissions? Last year, McKinsey released a study that attempts to answer this question. As Brad noted yesterday, McKinsey found that improving energy efficiency—through better insulation, more efficient lighting and appliances, and better fuel mileage in vehicles—is the cheapest way to reduce carbon emissions, with most efficiency improvements having negative life-cycle costs. (You'll have to read his post to find out why, if these changes have negative costs, we haven't already made them.) It also finds that wind, nuclear, rooftop solar, and combined heat and power from small natural gas turbines are all cheaper options for reducing carbon emissions than building coal plants with carbon sequestration. It's possible to quibble with the low cost estimate McKinsey gives for nuclear power, given that nuclear plant operators are able to socialize the risk of a catastrophic accident, but otherwise these findings adhere pretty closely to the conventional wisdom.

Of course, even if solar and wind are cheaper ways to reduce emissions, it's still an open question whether they'll be able to provide a large enough fraction of our electricity to reduce our carbon emissions by as much as we have to reduce them. The answer to this question depends on how much it will cost to solve the problem of wind and solar being intermittent sources of power. If we can do this economically—through either long-distance grid interconnections or better energy storage—then coal with carbon sequestration doesn't make sense. If we can't, then "clean coal" might start to become attractive on the merits, and not just because it plays well in swing states.

--Rob Inglis, High Country News