Coal is the major source of electricity in the United States and China. One solution that has been proposed to clean up the pollution from coal to combat global warming is clean coal technology. Coal is the dirtiest of the fossil fuels. According to the Energy Information Administration (EIA), coal generates half of the electricity in the United States and will likely do so as long as it is cheap and plentiful. According to the U.S. government, clean coal technology strives to reduce the harsh environ mental effects by using multiple technologies to clean coal and contain its emissions. Not everyone agrees, however, that clean coal is actually clean. Many groups criticize the technology, not convinced that it can do what it claims it can.
Most coal—92 percent of the U.S. supply—is used in power production. Power plants burn coal to make the steam that turns turbines and generates electricity. When coal burns, it releases CO2 and other emissions in flue gas. Some clean coal technologies claim to purify the coal before burning it. One method—called coal washing—removes unwanted minerals by mixing crushed coal with a liquid and letting the impurities separate from the coal and settle out to be removed. Other systems control the way the coal is burned in order to minimize the sulfur dioxide, nitrogen oxide, and particulate emissions. Wet scrubbers are also used. Also referred to as flue gas desulfurization systems, they remove sulfur dioxide—a major cause of acid rain—by spraying flue gas with limestone and water. The mixture reacts with the sulfur dioxide to form a synthetic gypsum (a component of drywall).
Low nitrogen oxide burners can also be used to reduce the creation of nitrogen oxides. Electrostatic precipitators are used to remove particulates that aggravate asthma and cause respiratory problems for people by charging particles with an electrical field and then capturing them on collection plates.
Gasification processes avoid burning coal altogether. With integrated gasification combined cycle (IGCC) systems, steam and hot pressurized air or oxygen combine with coal in a reaction that forces carbon molecules apart. The resulting syngas, a mixture of carbon monoxide and hydrogen, is then cleaned and burned in a gas turbine to make electricity. The heat energy from the gas turbine also powers a steam turbine. According to the U.S. Department of Energy (DOE), since IGCC power plants create two forms of energy, they have the potential to reach a fuel efficiency of 50 percent.
According to a report on CBS News, the cleanest coal plant in North America is operated in Florida by Tampa Electric. They call it clean coal, but they do not exactly burn coal. The process they use involves mixing coal with water and oxygen and converting it into a gas. John Ramil, Tampa Electric's president, said, "Gasifying coal allows the company to remove pollutants like sulfur, nitrogen, and soot, which virtually eliminates acid rain. And you can do it much cleaner than with the conventional coal technology."
James E. Hansen of GISS has another view on the issue. "There is no such thing as clean coal. All coal plants still emit millions of tons of CO2—the most threatening greenhouse gas. There is no coal plant that captures the CO2 and that's the major long-term pollutant."
Other scientists believe it is possible to recover most of the CO2 and store it underground—CCS. In Norway, one company is storing CO2 in rock caves beneath the North Sea. The DOE was planning a CCS project but halted it when the cost became too high.
In a study that appeared on the Web site LiveScience, a list was given of both the pros and cons of clean coal technology and related issues. The pros for pursuing clean coal technology are that the United States relies heavily on coal as a dependable source of power. Barbara Freese of the Union of Concerned Scientists (UCS) states that because of the United States' heavy reliance on coal as an energy source, "Weaning ourselves off of coal is obviously going to be very difficult and take some time. Given the unprecedented, urgent threat we face with climate change, we can't afford to ignore any technological option that could be part of the solution. We might need coal technologies to reduce our CO2 emissions more quickly than we could if our only technological options were renewable energy sources and energy efficiency strategies."
The cons of clean coal technology point to the fact that coal is a dirty fuel and not easy to clean. According to Freese, "You're taking an inherently very polluting fuel, with each pollutant posing myriad problems and solving each with different technologies, and that keeps adding up in terms of cost.
"Even if CCS works properly with coal exhaust, you're depending on a nonrenewable resource for energy, and one that's notoriously destructive of the environment when it comes to mining it out."
Industry and cities have several hurdles to overcome. As new technologies become more advanced, implemented, and affordable, shifts need to be made to cleaner, sustainable, renewable energy sources that do not have a negative impact on the environment.
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