Click image to open full size
Environmental Science
What Actually Happens to Your Recycling
Resin codes, MRF sorting, and true recycling rates
Related Tools
Related Labs
Related Worksheets
Related Cheat Sheets
Recycling is not a magic reset button, but a chain of physical sorting, cleaning, melting, pulping, and remanufacturing steps. After you put items in a bin, they usually travel to a Material Recovery Facility, or MRF, where machines and workers separate paper, metals, glass, and plastics. This matters because only clean, correctly sorted materials have a good chance of becoming new products. The rest may be landfilled, burned for energy, or shipped to another processor.
Key Facts
- A Material Recovery Facility, or MRF, sorts mixed recyclables using screens, magnets, air jets, optical scanners, eddy currents, and human quality control.
- Steel cans are pulled out by magnets, while aluminum cans are separated by eddy current systems that push nonmagnetic metals away.
- Plastic resin codes identify polymer type, not automatic recyclability: 1 = PET, 2 = HDPE, 3 = PVC, 4 = LDPE, 5 = PP, 6 = PS, 7 = other.
- In many U.S. programs, plastics 1 and 2 are most commonly recycled, 5 is accepted in some places, and 3, 4, 6, and 7 are often landfilled unless a local program says otherwise.
- Contamination rate = contaminated material mass / total collected recycling mass × 100%.
- Recycling works best for aluminum, steel, cardboard, paper, and clean PET or HDPE containers because these materials have strong markets and established processing systems.
Vocabulary
- Material Recovery Facility
- A facility that receives mixed recyclables and separates them into material categories for sale to processors.
- Resin code
- A number on plastic packaging that identifies the type of plastic polymer used to make the item.
- Contamination
- Unwanted material in the recycling stream, such as food, plastic bags, liquids, or nonrecyclable items.
- Eddy current separator
- A machine that uses changing magnetic fields to push aluminum and other nonferrous metals away from other materials.
- Downcycling
- The process of turning a material into a lower-value or less recyclable product after processing.
Common Mistakes to Avoid
- Wishcycling items that seem recyclable. This is wrong because nonaccepted items can jam equipment, contaminate bales, and make real recyclables harder to sell.
- Leaving food or liquid in containers. This is wrong because moisture and grease can ruin paper, attract pests, and cause entire loads to be rejected.
- Assuming every plastic number is recycled. This is wrong because resin codes identify plastic type, while actual recycling depends on local equipment, markets, and collection rules.
- Bagging recyclables in plastic bags. This is wrong because bags wrap around sorting equipment and may cause recyclables inside the bag to be treated as trash.
Practice Questions
- 1 A school collects 500 kg of mixed recycling in one week. If 75 kg is contaminated and removed, what is the contamination rate as a percent?
- 2 A recycling center receives 1200 plastic containers: 450 are PET 1, 350 are HDPE 2, 200 are PP 5, and 200 are other plastics. If only PET 1 and HDPE 2 are recycled, what percent of the plastic containers are recycled?
- 3 Explain why an empty, rinsed aluminum can usually has a better chance of being recycled than a greasy pizza box or a plastic item labeled 7.