Science of Coal – Video

Transcript:

This is a rock. But imagine if you could run your electricity system on it. You wouldn’t have to put it in a tank like oil or other liquid fuels. You wouldn’t have to worry about it floating away like a gas. You wouldn’t have to wear a special radiation suit just to handle it. And you wouldn’t have to wait for it to come around like sun or wind. It just sits there solid and dependable. Of course, these are exactly the benefits of the rock that burns: coal. It started as plants settle to the bottom of swamps. They were covered by sediment, compacted, and cooked into coal. Throughout geologic time, Earth has been hotter and wetter. Swamps and bogs were widespread, and in all these places today, we find coal. You don’t have to refine, purify, or enrich it. You just dig it out of the ground, store it in a heap- for a day or a decade- and burn it when you need it. It’s simple, available, and cheap, and that means coal-fired electricity is too. Nearly every Western country developed on it. Now China and India are too. It’s the engine that lifts countries out of poverty. Today, coal is the world’s leading electricity source, and global use continues to rise. But, for all its simplicity, coal is complicated. That’s its molecular structure. There’s lots of carbon and hydrogen in there, and when you burn coal, it makes heat. But all this other stuff causes emissions. The nitrogen becomes nitrogen oxides, which cause smog. The sulfur becomes sulfur oxide, which causes acid rain. These together are damaging to human lungs. They are heavy metals and toxins like mercury, lead, uranium, and arsenic mixed in with the coals and enormous volumes of ash that must be disposed of. And, of course, billions of tons of CO₂. Coal is our largest source, and in some places, mining coal can be dangerous and environmentally damaging. It’s often said there are no benefits without costs- certainly not in energy- and coal was perhaps the clearest example: simple, affordable electricity available in almost every country, offset by the fact that it’s dirty. That said, you’ve probably heard about clean coal, and we’ll talk about that next.

You just heard me say coal is dirty, but you might have heard politicians or television commercials talking about clean coal technology. What’s going on? They’re suggesting removing CO₂ from the emission stream to make coal clean. There are a few pilot projects to add units onto existing coal plants to capture carbon, and there are technologies proposed to turn coal into gas separating the CO₂ before it is burned. But both of these are too experimental and expensive to roll out at the huge commercial scales necessary to make a difference today. There are, however, technologies to reduce particulates and other pollutants produced by burning coal. What’s called the bag house, like rows of giant vacuum cleaner bags, can remove all the ash and some of the heavy metals. Scrubbers and catalysts capture sulfur oxides, nitrogen oxides, and some of the mercury. The best coal plants capture these emissions, but worldwide more of them don’t. Why? Because adding these processes is complicated and expensive, and that takes away some of the biggest benefits of coal: simplicity and affordability. And it takes energy to run all these processes, and that comes from the coal plant itself. Which means to produce the same amount electricity, the plant has to burn more coal, and that produces more pollutants and more CO₂. So we can clean up particulates and other pollutants from coal plants, but with greater cost, complexity, and carbon emissions.