CLEAN COAL?: According to the IPCC, the world will likely continue to rely on coal to generate a large portion of its electricity, necessitating technological fixes like undemonstrated carbon capture and storage to avoid catastrophic climate change. Image: © ISTOCKPHOTO.COM/WARWICK LISTER-KAYE
Power plants in the U.S. burned more than one billion tons of coal in 2006, according to the U.S. Department of Energy's Energy Information Administration. Nearly 400 million of those tons came from the region known as Appalachia, a swath of territory stretching along the spine of the Appalachian mountains from southern New York State to northern Mississippi. These ancient mountains hold high-quality bituminous coal, which fuels the aging coal-fired power plants that supply roughly 50 percent of the nation's electricity and more than 40 percent of the nation's emissions of carbon dioxide—the leading greenhouse gas. As a result, mountains are being leveled to get at the coal that lies below them, clearing forests, polluting streams and destroying the health of local residents. And, according to the most recent report of the Intergovernmental Panel on Climate Change (IPCC), this state of affairs is likely to continue as the U.S. and the world continue to burn coal for electricity.
"Certainly for the next several decades, the majority of electricity will be generated by fossil fuels in a fairly conventional way," says Bill Moomaw, an international energy policy expert at Tufts University's Fletcher School of Law and Diplomacy, primarily because it is cheap and readily available. "If we're going to continue to use coal we're going to have to have some way of reducing the carbon dioxide." As a result, the IPCC summary notes that carbon capture and storage—trapping the carbon dioxide before it escapes from the smokestack and pumping it underground—is a likely technology solution for mitigating climate change, along with a variety of other options. "There is no silver bullet," says Harlan Watson, senior climate negotiator for the U.S.
But carbon capture and storage will play a key role as coal continues to supply a significant portion of world energy supply and, unfortunately, it has yet to be demonstrated on any power plant anywhere. The U.S. Department of Energy (DOE) has at least 20 pilot projects to investigate it, according to Stephen Eule, DOE's director of the climate change technology program, but none have applied it on a commercial scale. A variety of techniques, including passing the remnants of coal combustion through an ammonium carbonate solution or separating purified CO2 from gasified coal, are possible—at a cost. "There is no plant that integrates gasification with capture and sequestration," says physicist Ernest Moniz of the Massachusetts Institute of Technology, who co-chaired a report on the future of coal. But "gasification looks today to be the lowest cost option with carbon capture."
That primary cost is in energy that gets used to capture the carbon—roughly 40 percent of the power a plant can produce—as well as to pressurize it and pump it underground. "In general terms, you are talking about a 50 percent increase in the cost of coal and maybe a 25 percent increase in the retail residential price of coal-fired electricity," Moniz says. "For a 600-megawatt power plant, in order to capture most of the CO2 and sequester it for the 50-year life of the plant, you're talking about one billion barrels of supercritical CO2. That's a pretty big reservoir."
And, although a few projects such as the Sleipner gas field in the North Sea or oil fields owned by the EnCana Corporation in Calgary, Alberta have proved that CO2 can be pumped underground and remain trapped below cap rock, they are aimed at enhancing recovery of the fossil fuels in those fields rather than permanently storing the greenhouse gas. "There's a high likelihood that if you choose your site well it will hold CO2 for hundreds of thousands of years," says S. Julio Friedmann, head of the carbon management program at Lawrence Livermore National Laboratory in California.
There are other technologies available, such as using algae to capture the waste greenhouse gases from power plants and turning it into diesel or other fuels. "The amount of CO2 that you capture [with algae] is very high and the amount of biofuel created per acre is incredibly greater than you can do with corn or even sugarcane," Tufts's Moomaw says. "The problem is it only works in the daytime." Alternative forms of power production, such as wind or solar, remain a small—albeit fast-growing—portion of world electricity supply. Even nuclear power is unlikely to play a major role in fighting climate change. "By 2030, we might be seeing something around 18 percent of power being generated by nuclear rather than the 16 percent we see today," Moomaw adds. "There are so many issues around nuclear power, we don't see it as being the answer to global warming and the electricity sector."