Tuesday, May 8, 2007

Climate Change: Coal Plant Mitigation and Replacement Strategies

If we are serious about doing something about climate change in the United States, a good place to start with with our coal-based electrical generating facilities, which together contribute 40% of all of the carbon dioxide emissions in the United States.

Scientific American has a very useful article about the strategies available to make serious carbon emissions from coal-based electric generating plants. Some highlights:

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. . . .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. . . .

"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."

. . .

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."

Read it all.

Unfortunately, it appears that the country may be increasing, rather than decreasing its reliance on coal. The Christian Science Monitor reports that at least eight electrical transmissionlines are being constructed with the aim of moving coal-based electricity to the Northeast. the result willlikely be an increased reliance on coal:

"This is really all about transferring inexpensive coal power into areas of the country that have higher-priced electricity," says Mark Brownstein, a managing director in the climate and air program at New York-based Environmental Defense. "These parts of the country have taken a stand to reduce greenhouse-gas emissions.... So these lines become pipelines that undo policy positions that the Northeast has taken."

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