Unlike pollutants such as sulfur dioxide, which is relatively easy to remove with a scrubber installed on the smokestack of a coal plant, CO2 emerges in a diffuse stream that is difficult to filter. To solve this problem, there are basically two choices. Option A: Build gasification plants, which use heat and pressure to gasify the coal, allowing the CO2 to be captured before combustion. Option B: Bolt a CO2 scrubber on the stack of a conventional coal plant. The problem with both options is that they are prohibitively expensive, jacking up the cost of the plant by at least 20 percent and lowering its output by up to 40 percent.
And even if somebody invents a cheap, efficient way to capture CO2 from existing coal plants, you still have to bury it. First, the CO2 gas must be compressed into a supercritical fluid — a process that uses up to 10 percent of the energy created by burning the coal in the first place. And pumping the liquefied carbon gas underground consumes even more energy. But the real problem for underground disposal ("storage" is an industry euphemism) is one of scale. The most significant storage project in the world today is located off the coast of Norway, where StatoilHydro, a large Norwegian oil and gas company, has been pumping 1 million tons of CO2 into a reservoir beneath the North Sea each year since 1996. It's an enormous engineering project, deploying one of the largest offshore platforms in the world. But compared to the engineering effort that would be required to stabilize the climate, it's inconsequential. It would take 10 Statoil-size projects to store the annual emissions of a single big coal plant.When you think about what it would mean to bury the CO2 from even a fraction of the coal plants in the world, the scale of this undertaking gets downright absurd. Vaclav Smil, an energy expert at the University of Manitoba, argues that "carbon sequestration is irresponsibly portrayed as an imminently useful option for solving the challenge" of global warming. Smil points out that to sequester just 25 percent of the CO2 currently emitted by stationary sources — mostly coal plants — we would have to create a system that would produce twice as much fluid every year as the world's crude-oil industry: an undertaking that would take decades to accomplish.
Then there's the question of safety. "If it's done right," says Susan Hovorka, a sequestration expert at the University of Texas, "the risks of burying CO2 are minimal." But if it's not done right, the buried carbon gas could migrate through cracks in the earth and, at high concentrations, create deadly pools of an invisible, odorless asphyxiant. Improperly stored CO2 could also trigger earthquakes or damage freshwater drinking supplies by pushing up salty brine from deep aquifers. Given the risks, Big Coal is likely to pass off the liability for these high-tech CO2 dumps onto the public, pushing for a version of the Price-Anderson Nuclear Industries Indemnities Act, which assures power companies that if their nukes melt down, they won't be liable for the full cost of the disaster.
Bottom line: Clean coal and carbon sequestration are disdainful lies purely designed as delaying tactic PR exercises to allow big coal to keep shoveling in the money while the world burns.