The IPCC recently stated that failure to deploy technology to capture carbon emissions from coal would double the cost of stopping climate change. Two coal-fired power plants nearing completion in Saskatchewan and Mississippi will be the first in the world to actually prove the technology, capturing their CO2 emissions and store that bolus of greenhouse gases underground. You can learn how they will do it in my latest for Technology Review. However, one point dropped from that story bears stressing. Part of what makes the extra cost of carbon capture feasible for these plants is that they have buyers for their CO2: oilfield operators who will use the stuff as a solvent to loosen up petroleum stuck in aging oil wells. That means the CO2 may not be permanently trapped underground warns Sarah Forbes, a carbon capture expert at the Washington-based World Resources Institute. In Canada ensuring CO2 stays underground is urgent, according to Robert Watson, CEO of SaskPower, the utility completing the coal-fired power plant in Saskatchewan. Watson told me that the oilfield operator taking his plant’s CO2 must ensure that any CO2 that comes back to the surface with produced oil is recycled back underground: “They’re going to have to assure the government that they can account for all of the CO2 they use all of the time.”