The Roots of Progress

What is charcoal? And how is it different from coal?

April 9, 2017

I’m in the stage of my reading where my knowledge of how much there is to learn is expanding faster than my actual knowledge. So the more I read, the more I realize how ignorant I am of the very basics of industrial civilization. So many simple questions I’d never even thought of, let alone knew the answer to.

Here’s one: What is charcoal, exactly? And how is it related to coal?

It turns out these two have nothing to do with each other. Coal is a rock you dig out of the ground (that much I knew). Charcoal is a man-made product, and it’s made from wood.

You make charcoal by heating wood to high temperatures in the absence of oxygen. This can be done with ancient technology: build a fire in a pit, then bury it in mud. The results is that the wood partially combusts, removing water and impurities and leaving behind mostly pure carbon.

The benefit of charcoal vs. wood is that it burns hotter and cleaner. The temperature is, I think, important for purposes such as smelting. The cleanliness matters for health vs. hazard of the working conditions around a furnace, and may also affect the resulting metal—I’m not clear on this part.

This general process of partially combusting a fuel by heating it in the absence of oxygen is called charring, and it can be applied to coal as well. Confusingly, charred coal is called “coke”. This was important for converting the British iron industry from wood to coal.

Update: Here’s a ~5-minute video of someone actually making charcoal from scratch in the woods (via the Primitive Technology channel on YouTube). Good illustration of the process.