Clean Coal?

This coal-fired power plant in Bridgeport, Connecticut was built before 1978, so its high pollution levels are "grandfathered" in. In 1997, coal plants spewed 12 million tons of sulfur dioxide. With "clean coal" technology, that number would have been two million tons.© Brian Howard

Coal still has many serious problems to overcome. According to the Natural Resources Defense Council (NRDC), the 100 coal plants that produce 57 percent of the electricity generated in the U.S. also produce 93 percent of the entire utility industry’s sulfur dioxide and 80 percent of its nitrogen oxide (both contributors to acid rain and smog). Coal plants are also major emitters of mercury, a highly toxic heavy metal.

Fifteen years ago, coal’s bad reputation was richly deserved. Since then, however, the DOE has spent billions of dollars to make coal cleaner. The results have been impressive: a state-of-the-art coal plant generates about the same amount of pollution as a natural gas plant, and it emits 62 times less nitrogen oxide than a conventional coal plant.

So why does the bad reputation persist? For one thing, most people don’t know that coal could be cleaner than it is. For another, coal plant owners tend to use the minimum amount of pollution-control equipment they can because it is very expensive. In 1997, for example, coal-fired utility boilers spewed out more than 12 million tons of sulfur dioxide. Without any environmental controls, the number would have been 20 million tons. With high-tech controls, the pollution would be cut to two million tons.

But the federal clean coal program also has its critics. The Green Scissors Campaign, noting that Congress had supplied $2 billion to the program since 1984, calls it "dirty pork in green clothing." Green Scissors says the clean coal projects "waste millions of taxpayer dollars on research that has already been done and that the coal industry should conduct with private funding." The General Accounting Office has also noted "serious delays or financial problems" in several clean coal programs.

One way coal plant owners avoid installing new equipment is by invoking a provision in the federal Clean Air Act that exempts certain plants built before 1978. If these plants have not made changes that increase the amount of air pollution they emit, or are not emitting any new pollutants, they do not have to satisfy the requirements. The Clinton Administration sued 32 plants that claimed to be exempt, but President Bush ordered a review of the government’s position soon after taking office. According to the NRDC, many electric utilities have indeed increased the amount of pollution they produce, but they justify the upgrades as "routine maintenance."

Coal’s other big handicap is its production of the main global warming gas, carbon dioxide (CO2). The U.S. generates 1.5 billion metric tons of CO2 a year, and coal is a major producer along with automobiles and other sources. Coal emissions are higher than for any other fossil fuel: A natural gas plant emits just 42 percent as much CO2 as a conventional coal plant.

One way to reduce a power plant’s CO2 emissions is to make it more efficient, which means getting more energy out of less fuel. So far, the best hope for improving coal’s efficiency is a process called gasification, in which coal is converted to a gas. A gasification plant is about 40 percent efficient, compared to the 33 to 36 percent efficiency of a conventional steam-driven coal plant. Small efficiency increases can produce big results: A 500-megawatt plant will generate 180 million fewer pounds per year of CO2 if its efficiency is increased just one percentage point.

Gasification plants cost between $1.2 million and $1.6 million per megawatt of capacity to build, compared to $550,000 for a natural gas plant and $1 million for a conventional coal plant. Consequently, the only gasification plants in the U.S. have been built with financial help from the DOE.

Gasification also works on municipal and hazardous wastes, neither of which emit carbon dioxide when burned. Global Energy, which specializes in gasification plants, is preparing to build a plant in Kentucky that gasifies a mixture of coal and municipal solid waste. The plant is expected to emit 60 to 65 percent of the CO2 produced by a conventional coal plant and eliminate 1.5 million pounds of waste that would otherwise be landfilled.

Global Energy will also try to use some of the gas to power a fuel cell, a device that produces energy but virtually no pollution. Fuel cells require very clean gas, so any success in powering one with gasified materials could be an environmental milestone. "The use of gasification to convert waste materials into fuel for fuel cells could literally solve two environmental problems at the same time," predicts Hazardous Materials Management magazine.

Another solution to CO2 emissions is carbon sequestration, a process that captures and stores CO2. The Massachusetts Institute of Technology (MIT) Energy Laboratory is working with seven energy companies to try and develop a cost-effective sequestration method. "It should be viewed as a complement, not a substitute, to improving energy efficiency," says MIT’s Howard Herzog. Sequestration eliminates all CO2 emissions, but it increases the cost of electricity to consumers by 66 percent, making it very unpopular with industry. "Without a government mandate, no one will do anything about carbon dioxide," says Phil Amick, vice president of development for Global Energy.

The DOE is trying to make sequestration cheaper and better through a number of programs, including "Vision 21," whose goals include 60 percent efficiency for coal plants, elimination of all CO2 emissions and obtaining commercial viability by 2015. Larry Ruth, who heads up Vision 21, says he is confident the U.S. can meet those goals.

Ruth says coal is cheap and plentiful, whereas natural gas supplies are limited, oil is relatively expensive, and renewables are not yet viable for large-scale power generation. "We must find better, cheaper, cleaner ways to use fossil fuels for a long time," says Ruth.

Green Scissors, however, counters that coal will never be truly clean. "Because of the basic chemical and physical characteristics of coal," the group says, "once [it] is burned, the reduction of CO2 emissions becomes economically impossible."