How steel and aluminum are recovered from electronics
Steel and aluminum are the cases, frames, fasteners and heat sinks of electronics, and they make up most of the metal by weight. They are also the most straightforward to recover: magnets take out the steel, eddy currents take out the aluminum, and both go back to a furnace.
This page describes industry and research processes in general. It does not describe ERI’s operations.
How much there is
Iron, steel and aluminum make up most of the metal in discarded electronics
Most of the metal in discarded electronics is structural metal, not the precious metal on circuit boards. The Global E-waste Monitor 2024 estimates that e-waste generated worldwide in 2022 contained about 31 billion kilograms of metals. Iron and steel accounted for roughly 24 billion kilograms of that, followed by aluminum at 3.9 billion kilograms and copper at 2.1 billion kilograms. Iron is also the metal recovered most successfully, because it is present in large quantities and is recycled at high rates in almost every e-waste management route.1
How they are separated
Magnets pull steel out of shredded electronics
After electronics are shredded, the fragments are typically sorted by physical properties such as magnetism, electrical conductivity and density. Ordinary carbon steel is magnetic and copper alloys are not, so a magnetic separator can lift steel pieces out of the mixed stream. The method has limits. Many stainless steels are not magnetic and are not readily captured by simple magnets. A part that was not fully broken apart, such as a small motor with a magnetic core and a copper winding, follows the steel and carries some copper along with it.2
Eddy-current separators sort aluminum from other materials
Aluminum is not magnetic, so it is commonly recovered with an eddy-current separator. Shredded material moves off a conveyor into a changing magnetic field, which is produced by permanent magnets or an electromagnet. Pieces of conductive metal are pushed away from the field and follow a different path from the rest of the stream. Light, highly conductive metals respond most strongly: aluminum is accelerated about twice as much as a copper piece of the same size. Poor conductors such as lead and stainless steel respond weakly, and glass and plastics do not respond at all.2
Back into production
Scrap steel goes to electric arc furnaces and scrap aluminum is remelted
Recovered steel and aluminum return to manufacturing as furnace feed. Steel scrap is typically melted in an electric arc furnace, where electric arcs, sometimes supplemented by natural gas burners, melt a charge that is mostly scrap. The U.S. Energy Information Administration reported that electric arc furnaces produced 60 percent of U.S. steel in 2011 and used more than 90 percent scrap. Aluminum scrap is treated, melted and then refined. Counting both manufacturing scrap and discarded products, scrap-based production accounted for nearly 60 percent of U.S. aluminum output at the time of that 2014 report.3
Recycling steel and aluminum uses far less energy than making them from ore
Making steel and aluminum from scrap takes far less energy than making them from ore. A 2014 analysis by the U.S. Energy Information Administration, drawing on estimates from the Environmental Protection Agency and the Department of Energy, describes recycling as the primary energy-efficiency technology in aluminum and steel manufacturing and as a main driver of energy-efficiency improvements in both industries. How much energy is saved depends on the metal and on the process used.3
What limits the quality
Mixed alloys, copper and coatings limit the quality of recycled metal
The quality of recycled steel and aluminum depends on how clean the scrap is. Conventional steel, aluminum and magnesium recycling cannot remove many dissolved impurities, so what goes into the furnace largely stays in the metal. A 2013 United Nations Environment Programme report states that copper above 0.25 percent by weight in steelmaking scrap makes steel brittle and unsuitable for high-quality products, and that tin also degrades steel. Aluminum can be recycled repeatedly if the scrap is pure. Otherwise contaminants must be diluted with new aluminum, and coatings and attached materials reduce the amount of metal recovered.2
Where each material sits
Steel
Steel in electronics: where it sits and why it is recovered has its own page, with every device here that holds it.
Aluminum
The 13 devices here that hold aluminum
| Device | Where the aluminum sits | How much |
|---|---|---|
| E-bike | Frame, rims and hub shell | Most of it |
| Hard disk drive | Cast bodies and the platters | Most of it |
| Laptop | Case, lid and bottom cover | Most of it |
| Cordless drill | Cell foils and the gear housing | A real share |
| Game console | Heat sink fins and shields | A real share |
| Robot vacuum | Foils inside the battery cells | A real share |
| Flat-screen TV | Frame and backlight heat spreaders | A real share |
| Smartwatch | Case, on many models | A real share |
| Solar panels | Frame round the glass | A real share |
| Circuit boards | Heat sinks and capacitor cans | A real share |
| Headphones | Sliders and hinge parts | A real share |
| Smartphone | Frame and mid-plate | A real share |
| Enterprise server | Processor heat sinks and drive casings | A real share |
Which devices feed this stream
These are sorted for steel and aluminum when they are recycled. Each page says what the device holds and where.
Sources
- The Global E-waste Monitor 2024International Telecommunication Union (ITU) and United Nations Institute for Training and Research (UNITAR), Chapter 6, Recovery of Valuable and Critical Metals, p. 44 (text and Figure 18); Executive Summary, p. 11
- Metal Recycling: Opportunities, Limits, InfrastructureUnited Nations Environment Programme, International Resource Panel (2013)
- Recycling is the primary energy efficiency technology for aluminum and steel manufacturingU.S. Energy Information Administration, Today in Energy (May 9, 2014)
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