Despite the rise of nuclear energy, biofuels, and hydropower, coal is still used to generate approximately half of the electricity in the United States. And as long as coal is plentiful and cheap--far cheaper than its clean--energy competitors, this setup is unlikely to change. Coal is known for being the "dirtiest" of all fossil fuels. Composed primarily of carbons and hydrocarbons, its ingredients help make plastics, fertilizers, and tar. A solidified carbon called coke, a coal derivative, melts iron ore and reduces it to create steel.
But most coal (92 percent of the US supply) is funneled into power production. Yet the use of coal has steep environmental consequences. When it is burned, it lets off emissions that create acid rain, pollute water, and contribute to global warming. "Clean coal" technology has been vetted as an alternative to the traditional burning of coal, the argument being that by "cleaning" coal and limiting its emissions, the fossil fuel can become a much more environmental friendly energy source.
One variety of coal preparation is known as "coal washing." In coal washing, crushed coal is mixed with a liquid in order to extract impurities and let them settle, thus removing unwanted minerals prior to burning. Other techniques center around controlling the burn process itself: wet scrubbers, or flue gas desulfurization systems, remove sulfur dioxide (a major factor in the creation of acid rain) by spraying flue gas with limestone and water. The mixture then reacts with the sulfur dioxide to form synthetic gypsum, a component of drywall. Low-nitrogen oxide burners reduce the creation of nitrogen oxides (which contribute to high ground-level ozone concentrations) by restricting oxygen and actively monitoring the combustion process. Electrostatic precipitators remove particulates that aggravate respiratory ailments by charging particles with an electrical field, and then capturing them on collection plates. "Gasification" eliminates the need to burn coal altogether: using integrated gasification combined cycle (IGCC) systems, steam and hot pressurized air/oxygen combine with coal. The reaction forces carbon molecules apart, and the resulting 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 simultaneously powers a steam turbine. And because IGCC power plants create two forms of energy, they have the added potential of being able to reach a fuel efficiency of 50 percent.
So what companies are in on the clean coal initiative? American Electric Power (NYSE: AEP) publicized its success in capturing and storing more than 37,000 metric tons of pure carbon dioxide from its Mountaineer smokestack (which would have otherwise entered the atmosphere unhindered)-however the project was ultimately shut down due to legislative and technical complications. Nevertheless, numerous other energy companies took notice, such as Cenovus Energy (NYSE: CVE), Statoil (NYSE: STO), LP Amina, Southern Company (NYSE: SO), and Shenhua Group, the largest coal company in the world. But despite its promises, clean coal will not spread until governments mandate it, either by regulating emissions directly or by imposing a price on the pollution generates by burning coal. Clean coal may be a look into the future, but is remains far too expensive to be profitable in the present.