There's no easy way to capture all the carbon dioxide from a traditional coal-burning station. "Right now, if you took a plant and slapped a carbon-capture device on it, you'd lose 25 percent of the energy," says Julio Friedmann, who studies carbon dioxide management at Lawrence Livermore National Laboratory. But a new kind of power station could change that.
A hundred miles up the Wabash River from the Gibson plant is a small power station that looks nothing like Gibson's mammoth boilers and steam turbines. This one resembles an oil refinery, all tanks and silvery tubes. Instead of burning coal, the Wabash River plant chemically transforms it in a process called coal gasification.
The Wabash plant mixes coal or petroleum coke, a coal-like residue from oil refineries, with water and pure oxygen and pumps it into a tall tank, where a fiery reaction turns the mixture into a flammable gas. Other equipment removes sulfur and other contaminants from the syngas, as it's called, before it's burned in a gas turbine to produce electricity.
Cleaning the unburned syngas is cheaper and more effective than trying to sieve pollutants from power plant exhaust, as the scrubbers at a plant like Gibson do. "This has been called the cleanest coal-fired power plant in the world," says Steven Vick, general manager of the Wabash facility. "We're pretty proud of that distinction."
The syngas can even be processed to strip out the carbon dioxide. The Wabash plant doesn't take this step, but future plants could. Coal gasification, Vick says, "is a technology that's set up for total CO2 removal." The carbon dioxide could be pumped deep underground into depleted oil fields, old coal seams, or fluid-filled rock, sealed away from the atmosphere. And as a bonus, taking carbon dioxide out of the syngas can leave pure hydrogen, which could fuel a new generation of nonpolluting cars as well as generate electric power.
The Wabash plant and a similar one near Tampa, Florida, were built or refurbished with government money in the mid-1990s to demonstrate that gasification is a viable electricity source. Projects in North Dakota, Canada, the North Sea, and elsewhere have tested the other parts of the equation: capturing carbon dioxide and sequestering it underground. Researchers say they need to know more about how buried carbon dioxide behaves to be sure it won't leak back out—a potential threat to climate or even people. But Friedmann says, "For a first cut, we have enough information to say, 'It's a no-brainer. We know how to do this.'"