Subtitles section Play video Print subtitles I used to be a coal miner, but now I'm a full grown coal adult! Hey there dirty dozens, Jules here for Dnews! At the second presidential debate, Donald Trump brought up clean coal. Now, we saw some tweets from you guys wondering what clean coal actually is! But before we can explain clean coal, you kind of have to understand why we use coal in the first place. Coal is incredibly important. It's cheap -- one of the cheapest sources of energy available. It is amazingly efficient for making electricity, and it's one of the most abundant energy sources in the world, even more so than oil. But it has one huge drawback. It is so dirty that people regularly die from its pollution. When coal is burned it releases chemicals like sulphur dioxide, nitrogen oxides, a little mercury, and carbon dioxide, not to mention a bunch of various particulates. These leak into the air and water and result in smog, soot, acid rain, global warming, and toxic air emissions. Those can cause asthma, lung cancer, various heart diseases, and other health problems. Not good. So, in an effort to placate people worried about dying just to get a little electricity, the coal industry heavily invested in clean coal. But Clean Coal is still coal. It's not a different kind of coal. It's just handled differently in the process of turning it into energy. The term Clean Coal is actually shorthand for Clean Coal technologies, which are designed to lessen the number of pollutants released in the production of energy. One such method is called carbon capture and storage, which is exactly what it sounds like. Carbon dioxide is separated from the air before it leaves a power plant or other production plant using a process called “absorption” or carbon scrubbing. This is where chemicals called amines are used to bind to the carbon dioxide and pull it out of the air. This gas is then piped underground, or “sequestered” so that it can't leak into the atmosphere. It can even be used to help depleted oil fields coax their last bits of oil to the surface. We have a whole video about CO2 scrubbing if you want to know more. Another popular method to end the infamous acid rain scares of the 70s and 80s was to wash all the sulfur out of coal before it made its way into a plant. And when I say wash, I mean literally, they would break it down into chunks and run it through a water tank which could include minerals like magnetite to increase the density of the liquid. The coal floats, because it is less dense, while the sulfur and other impurities sinks. A third clean coal technology is called “oxy-fuel combustion”. When coal is burned at a power plant, the exhaust, also called “flue gas”, is usually just pumped into the atmosphere. But oxy-fuel combustion actually reroutes this flue gas back into the plant, where it is paired with pure oxygen and reused to burn more coal. The reason they do this is because the normal air we breathe air has a ton of nitrogen in it, and when it's heated with the coal, it reduces its efficiency and creates more nitrogen byproducts. But when we reuse flue gas and combine it with pure oxygen, this solves both of these problems and allows for hotter temperatures and more energy extraction. There are a number of other methods, but despite these efforts, environmental activists call “clean coal” an oxymoron, since it's not quite the anti-pollution miracle that coal companies make it out to be. The problem is that these methods are incredibly expensive and energy intensive, and that money and energy has to come from somewhere. Some estimate that the addition of capture carbon and storage to a coal fire plant increases coal use by 25% while keeping electricity output the same. Another huge problem is that these byproducts aren't so much being eliminated as they are being moved elsewhere, which is more of a storage solution than an environmental one. And on top of all that, for those reasons, clean coal technologies are not particularly widespread, at least not enough to make a significant difference for the time being. In the end, clean coal helps stem pollution at the source, but it seems to help coal companies maintain their image more than it helps the environment maintain itself. If you've been a subscriber of DNews for a while, you might've seen some of our recent VR videos. It's a completely new way to tell stories, learn and experience the world, and we just launched a brand new channel called Seeker VR. You can view the videos in 360 from your phone or computer. Click now to watch, or visit the first link in the description. And make sure you subscribe to Seeker VR. So, coal burning can contribute to acid rain. But we don't really hear about acid rain anymore. We used to a lot in the 70s and 80s. Is it still a big deal? What ever happened to acid rain? You can find out in this video here. What other science issues have come up in this election that you wanna know more about? Let us know down below in the comments and don't forget to like and subscribe to DNews for more video every day.