Coal is one of the most important sources of energy in today’s word- both the US and China, the two largest economies, make heavy use of coal as a source of electricity. Coal’s value as a source of power has a price, however- it’s a nonrenewable resource that takes a long time to form. In this post, we’ll talk about the origins of coal, its role in power generation, and other uses for coal.
Coal is similar to oil in that it is formed from decaying organic matter. Coal specifically comes from dead plants that die in a marsh, swamp, or similarly wet area. An accumulation of wet, dead plants decays to form a substance called peat. Peat itself makes a useful source of heat and energy when burned- in antiquity, people could make their living cutting peat from peat bogs and selling it.
Coal: It’s all about pressure
Peat varies quite a bit depending on the heat, pressure, and composition of the peat deposit. The reason the peat can accumulate in a deposit at all without completely decaying away is the water. Because there is less oxygen in water than air, bacteria have a harder time breaking down the plant mass- the lack of oxygen slows down their metabolism. As a result, while water is a common element in peat formation, the other factors like local temperature, pressure from layers of peat pressing down from above, and other factors mean that peat is not a uniform substance.
After the peat forms and accumulates, it needs to undergo a series of chemical changes to become coal. The first stage is pressure. As peat accumulates, the bottom layers of the deposit experience greater and greater pressure as more peat mounts up above them. This pressure first squeezes out the water in the peat, drying it out. When more peat accumulates on top of dry peat, it presses down with even more force and the compression also starts to generate a little heat. This heat and pressure start to alter the composition of the peat. Many components of the peat, like methane, turn to gas and get squeezed out of the deposit. Gradually, different elements get turned to gas and squeezed out of the peat until the only one left is carbon, which has been compressed by the weight of the peat above it.
This process has distinct stages that have distinct results. Peat itself becomes lignite, which becomes sub-bituminous coal, which becomes bituminous coal. Finally, the peat becomes anthracite coal, and then graphite. Graphite is not coal at all, but a pure carbon substance that is most commonly used in pencils. All types of coal from lignite to anthracite can be used to produce power, although lignite is the lowest quality and anthracite is the highest. Lower quality coal burns less efficiently and gives off more pollutants due to the presence of impurities. All types of coal are in use in power generation. Even within these types, however, there is considerable variation in coal quality. For example, different regions of the US produce different kinds of coal that have different characteristics, like how much carbon they emit when burned or their energy density per unit of weight.
Coal is non renewable energy
The entire process of creating coal from peat takes both time and a large amount of plant life to supply the peat. That means that if people use coal faster than it is created in peat bogs, it will eventually be used up. This is a major potential problem because it is a major power source. The US produces a little less than half of its power using coal, and for some nations like China the level is even higher. Losing access to such an important element of the electricity generation system would have a profound impact on the world economy.
The way coal produces power is simple. In a power plant, the coal is burned under a large container of water. As the water heats up and boils, it becomes steam. The steam flows out through a system of pipes to a turbine, where its passage over the blades of the turbine causes it to move. As the turbine spins, it also spins a large magnet that is attached to the turbine. A rotating magnet inside a coil of wire produces electricity in the wire, and this is just a large-scale version of that effect. So coal is just the fuel that heats up the water to kick off the whole power generation sequence.
Coal and the environment
Finding a replacement for coal involves either locating a similarly energy-dense fuel to take on coal’s role in this process, or turning to alternative means of power generation like solar. The underlying obstacle is that coal is so efficient in terms of how much you need to spend in order to make electricity from it that there is not much interest in developing these alternatives.
Furthermore, coal is considered one the most harmful pollutants to the environment, especially low-quality coal. Depending on the practices and technology of the power plant and the mines, it is possible to significantly reduce the impact coal has on the environment. However, this is expensive, and developing nations that use coal frequently do not take these safeguards.
Coal is a paradoxical material. On the one hand, it has fueled a huge increase in global wealth through cheap power. On the other, it is nonrenewable and pollutes as it is burned. Future generations will need to come up with a coal replacement, because there is no way to make new coal once it runs out aside from waiting for peat bogs to produce more- and that can take hundreds of millions of years.