To make steel, you need to separate the oxygen from the iron and add a tiny bit of carbon. You can accomplish both at the same time by melting iron ore at very high temperatures (1,700 degrees Celsius or over 3,000 degrees Fahrenheit), in the presence of oxygen and a type of coal called coke. At those temperatures, the iron ore releases its oxygen, and the coke releases its carbon. A bit of the carbon bonds with the iron, forming the steel we want, and the rest of the carbon grabs onto the oxygen, forming a by-product we don’t want: carbon dioxide. Quite a bit of carbon dioxide, in fact.
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