Definition
An electric arc furnace is a furnace that makes steel by melting metal with the heat of an electric spark. Thick graphite rods are lowered through the lid until they sit close to the metal inside, and when electricity flows, a lightning-like spark jumps across the gap. That spark is called an arc, and its heat melts the metal in the furnace. Today, what goes into this furnace is mostly used-up steel or leftover bits from shaping steel, in other words, scrap.
The raw material comes from junkyards, not mines
A car that has reached the end of its life gets crushed into a square block. When a building is torn down, the rebar gets pulled out. Leftover trimmings from factories that cut and shape steel pile up too. All of this is called scrap.
What an electric arc furnace does is melt whatever you put in. The lid opens, the raw material is dumped in, thick graphite rods are lowered close to it, and electricity flows. The spark that jumps between them is so hot that it melts steel like soup. Once everything is melted, the mix is adjusted to the right recipe and the molten steel is poured out. Today, the most common raw material for this furnace is scrap.
Here's one thing people easily mix up. "Electric arc furnace" names a single piece of equipment that melts what you load into it. "Scrap recycling" is the work of collecting that scrap, sorting it, and delivering it to the furnace door. They sit at different layers of the story. If you use the two terms as if they meant the same thing, talk about raw materials and talk about equipment get tangled together.
A route that grew where scrap piled up
Scrap doesn't fall from the sky. The share that comes back at the end of its life only exists once steel made long ago has worn out. So places that have used steel for a long time have scrap stockpiled, while places that only just started building haven't had time to build up a stock.
There are two main ways to make steel. The blast furnace-basic oxygen furnace route starts from iron ore, and the electric arc furnace route starts from scrap. Where scrap was scarce, countries chose the route that starts from ore. Where scrap had piled up, the route that melts that scrap grew.
The result shows up clearly in each country's mix. According to World Steel Association figures, the United States makes most of its steel in electric arc furnaces, while China makes most of its steel through the blast furnace-basic oxygen route. Other conditions play a part too, such as electricity prices, plants already built, and government policy. For the same product, the two countries' process mixes are almost opposite.
It would be wrong to read this as a difference in technology generations. The electric arc furnace is not a new gadget. In the United States, these furnaces started running in the early 20th century. What divides the two routes is not new versus old technology, but the raw material.
To be more precise: the two routes use different raw materials
Other metals get mixed into scrap. Some, like copper, are hard to remove once they get in. That's why, for a long time, electric arc furnaces handled products with looser requirements, like rebar. A method of casting molten steel thin and rolling it flat right away widened their reach to broad steel sheet, but this limit coming from the raw material is still there.
There's a limit on quantity too. The amount of scrap that comes back at the end of its life is only as large as what society used in the past, so it can't cover all the steel the world uses in a year. That means the two routes can't simply be swapped for each other. When the raw material differs, the routes you can choose differ too.
Still, it's not true that only scrap goes into an electric arc furnace. There is also a route where ore is reduced with gas or hydrogen into solid iron, which is then melted in an electric arc furnace. The raw material is ore, but the furnace that melts it is an electric arc furnace. In places without a stockpile of scrap, a high share of electric arc furnaces usually comes from this route.
Emissions split sharply. By World Steel Association figures, making one ton of steel produces a little over three times as much carbon dioxide on the blast furnace-basic oxygen route as on the electric arc route that melts scrap. But the electric arc figure varies a lot depending on how the electricity is generated. Also, these numbers are compiled from data that member companies submitted voluntarily, so they don't cover the whole world.
Electric arc furnaces come with a different condition in return. They have to draw a huge amount of electricity all at once, so the cheaper the electricity, the better the location.
Common misconceptions
The electric arc furnace is a new technology.
The push to replace blast furnaces with electric arc furnaces to cut carbon is indeed growing, but the electric arc furnace itself has been around since the early 20th century. What divides the two routes is not technology generation, but how much scrap a country has stockpiled and how cheap its electricity is.
As long as you collect scrap, you can remake as much steel as you want.
Scrap that comes back at the end of its life only appears once steel society used in the past wears out. That share is tied to how much was used before, so it can't cover all the steel the world uses.
Where you meet it
A car crushed into a square block at a junkyard is shipped to a steel mill and comes out as new rebar.
Rebar and steel beams from a demolished building go back into an electric arc furnace and become molten steel.
In one sentence
An electric arc furnace makes steel by melting what you load into it with the heat of an electric spark. Today its raw material is mostly scrap, so this route grew up where scrap piled up.