What is clean coal?


Clean coal is not a type of coal. It is a way of burning coal that could help slow down global warming — someday. It is not commercially available now, but it might be in a decade or two. 

The reason scientists and energy companies are so interested in clean coal is that it may be the only way that we can continue to use coal long into the future without making the global warming problem worse. Some people want to stop using coal altogether, but others want to keep using it because there is much more of it in the world than there is oil or natural gas — enough to last hundreds of years. Coal is also cheaper today than any other fossil fuel. And unlike some renewable energy sources, like wind or photovoltaic solar, you can make electricity from coal day or night, windy or calm, and just about anywhere in the country.

It sounds perfect, but coal is also the dirtiest fossil fuel, in three different ways. First, the land and water near coal mines is significantly disturbed by some types of mining practices. Second, burning coal the way we do today leaves behind massive piles of toxic ash, and contributes to air pollution. Finally, burning coal puts lots of carbon dioxide, or CO2, into the air. It is a special kind of pollutant because it is the major cause of global warming. Coal emits more CO2 per unit of energy it provides than either oil or natural gas.

To keep that from happening, scientists have figured out ways to capture CO2 from coal plants so that it does not get released into the air. They also know how to pump the CO2 deep underground in places where they believe it can stay safely for hundreds or even thousands of years. The whole process is called CCS, or “Carbon Capture and Storage” (or “Sequestration,” which means the same thing). When people talk about clean coal, that’s usually what they mean. Different types of CCS technologies can also help reduce toxic ash and air pollution, in addition to reducing CO2. None of them, however, can change the need for mining coal.

There are a couple of problems with CCS, though. First, capturing and storing the CO2 adds costs. Second, while scientists and engineers are pretty confident that underground storage will work, it’s a complex process, and we can’t be certain that everything will work as planned until it is tried on a big scale. If the CO2 just leaks out again, you have not accomplished much. Many large-scale tests are scheduled over the next five to ten years to figure all this out. 

If clean coal does work, it will mean higher costs for electricity, but that is true for all low-carbon electricity. And it could eventually play a large part in fighting global warming.