When one thinks of the steel industry, they probably picture dirty foundry work, hot temperatures, Pittsburgh and other images of heavy industry. Most people probably do not picture recycling.

As it turns out, steel is the most recycled material on the planet, according to Napa Recycling, with 80 million tons of steel recycled annually in North America. Recycling steel is also much more energy efficient than extracting iron from iron ore. Each ton of recycled steel saves 2,500 lbs of iron ore, 1,400 lbs of coal, 120 lbs of limestone and uses 74% less energy. In fact, most steel products, such as structural steel used in I-beams and rebar, contain 93% recycled content.

How is steel recycled? In general, steel must be processed into small chunks, separated from other materials, melted in a furnace, then recast into sheets, molds or structural shapes. Some structural steel components do not need to be remelted, especially if they will be used for other purposes, such as art installations.

Structural steel, automobiles and appliance bodies make up the bulk of the steel that is recycled each year. To trace how steel is recycled, one can trace the end-of-life cycle of an automobile.

Processing of scrap automobiles

At the end of a car’s usable life, it is sold for scrap. These vehicles either go to a junkyard, where they sit, picked apart by mechanics for usable parts, or to a scrap yard, where they will be processed quickly. In either case, their ultimate destination is a scrap yard for recycling.

For safety, some components are removed immediately, such as airbags and fluids from the fuel tank, A crushed car is loaded onto a conveyor by a claw excavator for shredding.A crushed car is loaded onto a conveyor by a claw excavator for shredding.engine, transmission, differential and radiator. Older vehicles may have mercury switches for the lights in the trunk, and those must be removed. Other parts are removed for higher resale, such as wheels, stereo equipment and some aftermarket parts. The catalytic converter is removed, as it contains platinum as a catalyst, and it can be recycled, and is of high value.

Once all of the dangerous or valuable parts have been removed, the car is evaluated for further part removal. Some operations will remove some of the larger non-ferrous parts, such as the radiator, wiring harness and engine block, especially with the rise of aluminum blocks and heads. Because the vehicle will be destroyed, little care is taken in removing these parts, and they are often ripped away from the steel unit body with an engine biter or the claw attachment on an excavator.

At this point, the remnants of the car are mostly steel, so it is ready to be crushed.

Car crushing

There are two popular styles of car crushers, both of which are operated by a gasoline or diesel engine and use hydraulics as the crushing force. A vertical has a bed, with a vertical crushing plate that is pressed down on the roof of the car, until it is approximately 18 inches to 30 inches high, depending on the crusher. The other style is a baler, which tends to crush the car into either a cube or a rectangular prism. In the U.S., the vertical crusher is more popular.

Before crushing, an excavator may smash the roof or pick up the car and drop it. This extends the life of the crusher’s hydraulics by weakening the structure. Modern automotive design tries to strengthen the vehicle in case of an accident, meaning all of those strengthening mechanisms must be overcome to crush the car.

The crushing action only takes a few seconds. A forklift is used to load the car, and typically braces against the doors during the crushing, or lelse the doors will bow outward, and may fall off the car during crushing. The crusher has enough force to damage the shocks and struts, so they collapse as well. Often, multiple cars are crushed on top of one another, and a stack of five to eight cars is removed from the crusher at once.

The cars are now ready to be shredded.


Metallurgical plant managers learned long ago that smaller pieces of scrap melt much more efficiently than larger pieces. Larger pieces have larger air gaps between them, meaning a heat with large pieces will yield less steel than a heat with smaller pieces. Shredding takes the larger pieces and makes them smaller for more efficient packing in the furnace.

Some scrap yards have a shredder on site, and others ship their cars to a shredding company. Shredders are a significantly more costly and higher maintenance devices than the crushers, so smaller junkyards opt to ship the crushed cars. The cars are wrapped in a netting to prevent pieces from falling off, and are loaded onto flatbeds for transportation to the shredder.

The shredder has two slow speed wheels, lined with a series of protrusions, called hammers. The wheels have no space between them, only slots where the protrusions are missing. Each crushed car is forced, often by gravity, into these wheels, and the hammers rip the steel apart like large scissors. On the opposite end of the shredder, fist-sized pieces of shredded metal drop into a bin or railroad car. Crushed cars are still recognizable, but the shredded pieces bear no resemblance to the cars they once were.

Separating metals

Often, there is a system for sorting metals during the shredding operation. All of the seat cushions, dashboard, plastic bumpers, trim and so on is called “fluff,” and it is lighter and separated by compressed air or gravitational methods. Removing the fluff keeps the steel mill running cleaner, as the fibers burn in the furnace.

The remaining metal pieces are fed through a series of conveyor belts. Magnetic belts are used to remove any ferrous material. Non-ferrous metals, such as aluminum, copper and magnesium, can be separated using eddy currents.

At the steel mill

Shredded steel is typically delivered to the steel mill in railcars. The metallurgical engineer will develop a recipe for batching the heat, which will include a certain percentage of scrap material and master alloys (which contain some additional alloying elements).

These ingredients are loaded into a clamshell bucket, which is dumped into the furnace. The lid of the furnace is closed, and three large electrodes slide into openings in the lid. Electric current in excess of 40,000 A flows through the electrodes, melting the steel in a few minutes.

Final thoughts

It can be a little depressing to walk through a junkyard and realize all of these cars once brought someone joy, but will soon go through a literal hell. However, the family minivan with the blown engine may someday be the I-beams that make up the next tallest building, or the sheet metal in the next race car. Steel’s recyclability means the family minivan will reincarnate as new goods for generations to come.

To contact the author of this article, email GlobalSpeceditors@globalspec.com