[SOUND] [SOUND] Welcome back to What You Need to Know. We're still on fossil fuels, and we've finally come to the original fossil fuel, to coal. It's one of the most plentiful resources usable for energy on the planet. Coals is what fueled the Industrial Revolution. You could burn something to make steam and from that steam, you could make all sorts of engines and machines work. So let's start by examining what is coal? Well, it too is dead plants and animals buried at high temperatures and pressures for millions of years. But the difference is that coal comes from a fresh water environment from peet bogs. It'll be from the center of continents where freshwater has accumulated overtime as opposed to the edge of continents. Or at least of continents 100 million years ago. Where dead plants and animals fell into marine environments, to saltwater environments. Also, the need for some type of geological trap is absent because coal is a solid. And that's also likely why there is so much more of it. When we described the range of natural gas to crude oil to heavy oils to toxins, all of that came on the same spectrum of carbon use. The light hydrocarbons, the gaseous ones those are natural gas. The one, two, three, four the liquid ones five through about 12 right, that's what we think of as crude oil. Little bit higher maybe some heavier oils, colder climates heavier, those types of oils turn into tars. Still though, they're simple compounds made up of carbon and hydrogen in a ratio of about two hydrogens per carbon. If we go all the way to the lightest one, to methane, it has four hydrogens per carbon. Coal chemically is about one hydrogen per carbon. But the formula for coal is not just something I can write down. All of the carbon chains are interconnected with each other. This diagram is a diagram of a quote typical coal molecule. Well, it isn't really a molecule. Even in this diagram the bonds will continue linking more and more carbon chains together. You can see there are a lot of this cyclic bands of hydrocarbons. Every time there's a veracity there's really a carbon atom there. There's some double bonds, lot of carbon double bonds. You see hydrogens sitting out and some oxygen. And occasionally on this diagram there's an r, a radical, something other than hydrogen and oxygen and carbon in the system. Since coal is made up of all of these different mish mash of rare earths and materials, just about everything could be in coal. It's very useful to be able to identify where a certain coal has come from. We could even think of the epidemiology of coal, the distribution of where the things that are left from coal are across the planet. Or across a place that might have been hit by pollution. How do you know that this lake was turned to by coal power plant? Well if the muck in this lake has the same distribution of rare earth as the coal that this power plant has used for the last 50 years, it's a pretty safe bet. What about this chunk of coal? This chunk of coal is Illinois number six. Coal that's used at the Abbott Power Plant at the University of Illinois. On an atom to atom basis I said coals about one to one with carbon and hydrogen. Maybe one to one with coal carbon and then hydrogen and oxygen. But we can also measure it by weight. Hydrogen weighs much less, so this case, this coal is 70.8% carbon and 4.7%, by weight, hydrogen. The largest component after carbon is oxygen, actually 10.3%. All of those things carbon, hydrogen, oxygen are going to turn into carbon dioxide or water vapor if it was burned completely. There are other things in coal too, particularly sulfur. Illinois coal is considered a high sulfur coal any coal higher than 1% sulfur is considered high sulfur. And this coal has 3.4% sulfur. It also has 1.1% nitrogen. When you burn sulfur, you get sulfur dioxide. When you burn nitrogen you get a variety of nitrous oxide compounds. Those two gases unlike CO2 can fairly easily combine with water vapor and form sulfuric and nitrous acid, the seeds for acid rain. So when burning coal, sure you'd love to get rid of the CO2 also. But that's the whole point of why you're burning the coal, you have to get energy. The SO2 and the NO compounds that you make, you want to somehow try to remove. Or of course if you bought coal in the first place that had less sulfur and nitrogen you'd be ahead of the game. Notice that these percentages have not added all the way up. There's two other components of coal, one is water. This coal is 2.7% water. And when you heat that up the water of course just turns into steam. It's also 7.1% ash. Pieces the coal that are basically compounds like rocks, with the same material that go into rocks. Compounds that are already very stable and don't burn. And this will just have to be removed when you burn the coal. So just by looking at the chemical composition of coal, you can see that to use it as a clean energy source we're up against a few tough things. We're going to have to remove the sulfur and nitrous oxides. And we're going to have to deal with the ash, the part of the coal that doesn't burn. And because coal has so many carbon-carbon bonds and carbon-carbon double bonds. It'll be very difficult to burn all of the carbon completely. Likely end up with some black smoke as well. Some unburned hydrocarbons or carbon that goes up the smokestack. So how did coal get that way? And why is there such a large difference? Let's take the journey from those dead plants and animals. Peat bogs are great illustrations today of the type of primordial swamp that grew these fossil fuels in the first place. Things fall into them, when they fall into them, they decay, they get compressed as more stuff falls in, more waters there. This material gets more and more compressed, and maybe eventually the water drains out. Unlike the oil wells which are found very, very deep cause a geological trap was needed. Many coal reserves are just under the surface. The first step on the way to making coal is to make a substance called peat. After all, when we have a peat bog it's because a lot of this vegetation mass that has been turned into some solid substance is the solid substance of peat. Here's a nice chunk of peat that I got from Ireland. You can even see a root growing in it. In fact an amazing thing about Ireland is if you just go out into the countryside, scrape away some of the very top soil and grass. Right under it is maybe a meter thick of peat. With a good peat shovel you can dig down and just get out chunks what looks like you're digging dirt, except it burns. Peat is something up to 25% pure carbon. Now that's 75% of stuff that doesn't burn, but 25% burns. And you can put chunks of peat like you would chunks of charcoal right into the fireplace, add enough air and dry out and you will have a peat fire. Very romantic, has a particular smell. You might recognize the smell if you're a scotch drinker. The difference between scotch and other distilled alcohols. Is that the process by which you stop the grain from growing after it's malted is typically done with a peat fire. This imparts some small amounts of taste of heat into the scotch itself. So you can burn peat, but you get a lot of smoke and you have a lot of ash. It's great you just going to keep your fireplace, there's not a lot trees perhaps in Ireland, but they've got dirt that burns. Let's say you're in a different geneology and the stuff got buried deeper and was buried for longer. The next thing that comes on a scale of carbon-coal lie products is called lignite or brown coal. This is in the range of 25-35% carbon. Germany has extremely large reserves of brown coal. Not too far down below the surface entire mountains effectively of this stuff that can be burnt. 25 to 35% carbon, two thirds stuff that does not burn still very smokey. Go a bit further deeper, longer times you reach sub-bituminous. This coal is in the 35 to 45% carbon. We have these names, but really there's a whole spectrum, right? You can have some deposit that's anywhere on the spectrum, just need a different name for it when it reaches a different substance. And then finally, we'll get to bituminous coal. The type of coal that's illustrated here in my hand the Illinois number six, that's 70% carbon. Bituminous has a large range, 45 all the way up to 85%. This is the bulk of coal resources across the world. Occasionally you can find some coals that are even purer carbon, the 85% to 95%. And this is called anthracite. Anthracite is very desired because of the high carbon content. It burns with very little ash left over and it can burn therefore at a much hotter temperature. Anthricide is sometimes called metalogical coal. Coal that was used to make metals. They heat the crucibles that would melt the ore into metals, iron itself. Another fun thing is that if you have a train, as we did in the turn of the century and it's being powered by coal. Coal is more efficient than wood. You have more energy density out of it. You didn't have as much water vapor in the wood. So you run your trains off of coal. And someone would be shoveling the coal into the boiler. You think about it, the engine is at the front of the train. Because it's pulling the train. And this engine where it has the coal boiler and the person shoveling the coal in. Obviously needs a smokestack for all the smoke coming out from burning the coal. And the smoke goes where? To all the passengers. Because the trains moving, so clearly the smoke is going to go right over the path of the train. Right into all the cars. At the turn of the century, riding a train meant you were going to emerge covered in coal dust and smoke and soo. Riding a train was not at all, something you would do in a white outfit. Say a white dress. If you take anthracite, well actually, if you take the stuff that would turn into anthracite. And you have the particular area where there was more temperature pressure, just the right conditions. You can make graphite. Graphite is 100% carbon. Probably not the best thing for burning in fact, it's very difficult to burn. If you pulverize it enough, I'm sure you could. But just chunks of it, you won't. But graphite's very useful. It's a useful, chemically useful thing to make stuff out of, pencil lead. It's graphite with some clay added to it usually. Nothing with lead by the way. And if you're extremely lucky and you bury the material that will turn into coal or graphite just right, you can make diamonds. Right for example right here. But diamonds again are pure carbon, different crystal structure than graphite but pure carbon nonetheless. Which does have its origin ultimately in the same fossil fuel family. That's what you need to know about what coal is. [MUSIC]
