#1179 What is the difference between coal, coke, and charcoal?

What is the difference between coal, coke, and charcoal? Charcoal is made from wood, but coal and charcoal are both sedimentary rocks that are processed differently to produce different results. Charcoal, coal, and coke all have different advantages, disadvantages, and uses. Let’s look at them one by one.

Charcoal is made from wood. If you want to start a fire, then wood is probably your go to material. Wood burns very well, assuming it is dry. However, if you want a hotter fire, charcoal is a far more effective fuel than wood. When you start a wood fire, the temperature slowly rises and the water in the wood evaporates. The drier the wood, the less water there is, but this is the first step. Quite a lot of the energy from the heat is wasted evaporating the water. Once the water has gone, the wood continues to heat up and releases carbon dioxide, carbon monoxide, acetic, and formic acid. These gases burn and that is the flames we can see. Once the wood gets to 280 °C, the heated wood reacts with the oxygen in the air and forms water, carbon dioxide, and other things. This is the reaction that produces the heat, although a wood fire won’t get hotter than about 500 °C. To make charcoal, wood is burned in an airtight space, something like an oven. Because there is no air in the oven, the water and the other gases evaporate and burn out of the wood without the wood itself actually burning. This removes the first few steps of wood burning and when you light the charcoal it goes straight to the producing heat stage. Charcoal can burn a lot hotter than wood, reaching temperatures of 1,100 °C, if extra oxygen is supplied with a bellows. Charcoal also doesn’t release smoke because all of the gasses have gone. It was thanks to charcoal that people were able to melt iron and the Iron Age started. However, charcoal is very expensive and bad for the environment. It is a huge cause of deforestation. If charcoal was the only source of energy we had available, the Industrial Revolution would probably never have started.

Coal and coke come from a sedimentary rock that was made millions of years ago when plant life was compressed under great pressure and temperature. When trees die on land, they oxidize, are eaten by living organisms, and they biodegrade. When the trees are on wetlands, they die and sink into the water or mud. There, they are protected from the oxygen and they get converted into peat. Over millions of years, the peat builds up and more and more layers of rock and dirt build up on top increasing the pressure. The pressure crushes the peat and a lot of the water and gases come out, leaving the carbon. This is coal and coke.

The difference between coal and coke is their price, the impurities they contain, and their uses. Coal is the sedimentary rock taken directly out of the ground. We always hear that we are running out of oil, but we are not running out of coal. There are approximately 1.16 trillion tons of coal left, which would last 133 years at current usage rates. However, we are not using as much coal as we used to because of its effects on the environment. Coal was the fuel that powered the industrial revolution, but it is not perfect. It is plentiful, and fairly easy to mine, but it is full of harmful substances. When burned it releases sulfur dioxide, nitrogen oxide, and other harmful things, along with enormous amounts of carbon dioxide. It is a significant factor in acid rain, smog, and climate change. Coal also contains a lot of water, which reduces its maximum temperature to about 1,000 °C.

Coke comes from the same source as coal, but it has been treated. It is burned without the presence of oxygen, in the same way as charcoal. This evaporates off the water and burns off a lot of the volatile gases. This gives coke the same advantage as charcoal because it doesn’t need to use energy evaporating off the water before it burns and it can reach a higher temperature. Coke can reach 1,200 °C. Coke is usually used in the steel smelting process. If there is a good oxygen source into the furnace, it can reach very high temperatures. The coke is better for burning than coal, but it is still bad for the environment. Charcoal, coal, and coke are all made of carbon, so when they are burned, a lot of carbon dioxide is released into the atmosphere, which makes climate change worse. And this is what I learned today.

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