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You drop a bottle, a can and a cardboard box into one bin. A few days later they need to become three separate streams of clean material. Nobody at the facility knows what you intended. The equipment sorts by physical properties such as size, shape, what the material reflects and whether it is magnetic.
This guide traces a fictional bin through a typical sorting line. Real facilities differ in their equipment and order, so treat the sequence as a model and check your own program for the rules that apply to you.
The short answer
Collected, sorted by machines and people, then sold as material.
A collector takes your recycling to a materials recovery facility. There, screens separate items by size and shape, optical sensors and air jets pick out paper and plastics, a magnet pulls out steel and an eddy current pushes out aluminum. Each sorted material is pressed into bales and sold to plants that make new products. An item is only recycled if your local program accepts it and the line can recover it.
The method
The four stages of recycling.
EPA describes recycling as a loop. A break at any stage stops the material from becoming a new product.
01
Collection
A private hauler or local government collects recyclables. Your local program decides which items it takes, so its list is the rule for your bin.
02
Sorting and processing
A materials recovery facility separates the mixed load into single materials, removes what it cannot use and cleans or prepares the rest.
03
Manufacturing
Sorted material is sold, usually as bales, to plants that turn it into new products such as paper, containers or metal.
04
Buying recycled
Products made from recycled material need buyers. EPA counts buying them as the step that closes the loop.
Inside a sorting facility.
One public facility, run by Wasatch Integrated Waste Management District in Utah, publishes its sequence. Workers first remove items that could jam the machines. A rotating drum screen called a trommel then separates material by size, and a disc screen separates flat items such as paper from round ones such as bottles and cans.
Optical sorters combine near infrared, color and metal sensors. When a sensor identifies a target material on the belt, a blast of air knocks it into a separate chute. A drum of permanent magnets pulls out ferrous metal such as steel cans. An eddy current separator then repels non-ferrous metal such as aluminum over a divider. Each recovered material is pressed into bales and tied for delivery to buyers.
Notice what the machines respond to. A magnet does not know that a steel can once held soup; it only responds to iron. An optical sorter identifies material from what it reflects. That is why shape, cleanliness and packaging affect whether a recyclable item ends up in the right stream.
Original example: a bin holds a flattened cardboard box, a steel food can, an aluminum drink can, an empty plastic drink bottle, and a plastic grocery bag tied around five more bottles. Follow each item through the sequence above.
The cardboard is large and flat, so the screens send it toward the paper stream. The steel can follows the containers until the magnet lifts it out. The aluminum can is not magnetic, so it passes the magnet and is thrown out by the eddy current. The loose bottle is identified by the optical sorter and blown into the plastics chute.
The tied bag is the problem. The Wasatch facility uses spikes in its trommel to rip bags open, yet it warns that bagged recyclables will likely not be recovered. Five bottles that would each have been sorted loose may now leave the line together as waste. EPA also says plastic bags and film cannot go in a household recycling bin, although many stores collect them separately.
The number inside the triangle of arrows is a resin identification code. EPA explains that these symbols identify the type of plastic used to make the container. The code helps you look up whether your program takes that plastic. By itself, it does not mean your community collects the item.
Two items with the same number can get different answers. A program might accept a bottle but not a tub or clamshell made from a similar resin, because what a facility can sort and sell depends on its equipment and buyers. Read the item type and the number together, then check them against your local list.
Why a wrong item can cost a right one.
Anything that is not an accepted material is contamination. It takes worker time to remove, can jam equipment and can lower the quality of a bale. Food residue matters as well: EPA states that items with food debris cannot be recycled, and that spatula-clean is clean enough for accepted containers.
This explains a common surprise. Adding a doubtful item does not give it a chance to be recycled; it gives the facility one more thing to remove, and it can drag accepted material down with it. When you are unsure, the local program's list or search tool is the check. Do not substitute another city's rules, because facilities and markets differ.
Try three sorting checks.
Use the line described above and assume a program that accepts cans, cardboard and plastic bottles loose in one bin. For each item, predict what happens before reading the answers.
1. A rinsed aluminum can. 2. Six clean bottles packed inside a tied plastic bag. 3. A plastic tub marked with a resin number that the local list does not mention.
Answer check: the can passes the magnet and is recovered by the eddy current separator. The bagged bottles will likely not be recovered, even though each bottle alone would be accepted; empty them loose and take the bag to a store drop off if one exists. The tub is not settled by its number. Check the local list for that item type, and if it is not accepted, keep it out of the bin.
Transfer case: a friend says a coffee cup must be recyclable because it is mostly paper. What would you ask? One reasonable answer is: does the local program accept that specific item, and can the facility separate the paper from any plastic lining or lid? Material content alone does not answer either question.
Learn more about how materials move.
If you want to understand recycling, waste or the chemistry of everyday materials beyond one bin, try Cadence. We make the app. Describe what you want to understand and answer the setup questions to build a course around your starting point.
Adapt one of the suggested goals below to your own question. Cadence builds your course after setup; it does not know your local recycling rules, so check those with your program. Cadence offers lessons and practice at your pace. The checks on this page are complete without the app.
Free recycling sorting worksheet
Predict where each item goes before you check.
Use the fictional bin or items from your own kitchen. No account or location is needed.
RECYCLING SORTING WORKSHEET
Learning Cadence | Original exercise | 1 November 2026
YOUR ITEM
Item and what it is made of:
Shape (flat, round, small, large):
Is it magnetic? (try a fridge magnet on a can):
Resin number, if plastic:
Clean, or food residue left:
Does your local program list this item type? Source checked:
PRACTICE
A program accepts cans, cardboard and plastic bottles loose in one bin.
1. A rinsed aluminum can. Which machine recovers it?
2. Six clean bottles inside a tied plastic bag. Are they likely to be recovered?
3. A plastic tub with a resin number the local list does not mention. Does the number make it accepted?
ANSWER CHECK
1. Not the magnet. The eddy current separator repels non-ferrous metal such as aluminum.
2. Likely not. Bagged recyclables are hard to recover. Put the bottles in loose and take the bag to a store drop off if one exists.
3. No. The number identifies the resin, not local acceptance. Check the list for that item type.
TRANSFER
A paper coffee cup with a plastic lining. What two questions settle whether it belongs in your bin?
Answer: Does your program accept that item, and can its facility separate the materials? Paper content alone does not answer either.
Facilities differ in equipment and order. Your local program's current list is the rule for your bin.
Put it into practice
Understand the materials behind the bin
If you want to learn how materials, waste and recycling work, try Cadence. Describe your goal and answer the setup questions. Cadence is our app.
No. EPA explains that the number identifies the type of plastic. Whether your community collects that item depends on your local program.
Can I put recycling in a plastic bag?
Usually not. One facility that publishes its process warns that bagged recyclables will likely not be recovered, and EPA says bags and film cannot go in household recycling bins. Many stores collect bags separately.
How are aluminum and steel cans separated?
A magnet pulls out steel, which contains iron. Aluminum is not magnetic, so an eddy current separator repels it into its own stream.
Do I need to wash containers before recycling?
EPA says items with food debris cannot be recycled and that spatula-clean is clean enough for accepted containers. Follow your local program's directions.
See it in concrete terms
Explore example courses for your goal.
Adapt one of these starting goals to the materials question you want to understand. Answer the setup questions in Cadence; none of them is a fixed recycling course.
We followed EPA's four-stage description, used one public facility's published sorting sequence as the model line, then wrote an original bin trace, three checks with answers and a transfer case.
What we checked directly: On November 1, 2026 we read EPA's recycling basics page (updated June 22, 2026), EPA's common recyclables page (updated May 19, 2026) and the Wasatch Integrated facility description, and matched each machine step and claim to those pages.
Limits of this review: We did not visit a facility, test sorting equipment, check any city's acceptance list or measure environmental benefit. The bin and items are invented teaching examples, and facility layouts differ.
