Fossil Fuels: Carbon Capture and Storage
Despite efforts to switch to clean sources of energy, coal will be part of our future, at least for the next few decades. It's cheap, there's a lot of it, and we know how to use it—in the short term, coal remains the surest way to satisfy the world's enormous appetite for electricity. But since burning coal is a dirty enterprise that pollutes our atmosphere with CO2 and other compounds, experts are working on ways to clean up coal.
One way to make coal cleaner is carbon capture and storage, or CCS. In CCS, which can be used at both coal and natural gas plants, CO2 gas is captured before it can escape to the atmosphere. The gas is then turned into a fluid and injected deep underground.
CCS can be used with common fuels—coal or natural gas—available in many parts of the world. In fact, the U.S., Russia, China and India—four of the world's most energy-intensive countries--hold about 67 percent of the world's coal reserves.
CCS technologies significantly reduce CO2 emissions to the atmosphere, but they do not eliminate all the other environmental problems associated with burning coal.
CCS is already being tested and refined at several industrial operations around the world.
Coal-fired power plants retrofitted with CCS are not as efficient as regular coal plants. Building, maintaining and operating new, efficient CCS coal plants is also expensive, but electricity from such plants could be cheaper than solar energy.
Storing fluid CO2 underground works on a small scale, but large-scale tests at a variety of sites are still needed. It's possible that unexpected problems could crop up when storing large amounts of CO2 underground.
A big task.
CCS must be deployed on a massive scale to have a significant impact on CO2 emissions.
90% of CO2 emissions from the latest-generation coal-fired power plants could be stored underground.
Many experts argue that CCS is necessary. If the technology becomes widespread, coal could continue to provide much of the world's energy supply well into this century--while contributing very little to greenhouse warming. And most scientists think there's room underground in certain kinds of rocks for all the CO2 that we could produce from burning coal, although some sites may not be conveniently located.
Since 1996, this offshore oil platform has extracted natural gas from two gas fields below the seafloor. About 9 percent of the recovered gas is CO2, about 70 percent of which is separated out, liquefied, and injected into the Utsira formation—a 250-meter- (820-foot-) thick layer of sandstone about 1,000 meters (more than 3,000 feet) below the seabed.
The Right Rock
The Utsira formation in the North Sea is an ideal site for storing fluid CO2: the formation is enormous and could store several centuries worth of CO2 emissions from European power plants. Further, an 80-meter (260-foot) layer of impenetrable shale rests on top, preventing CO2 from escaping. Similar sites exist around the world deep below both ocean and land.