Many localities require residents to remove bottle caps from bottles before placing them into recycling containers. Caps have a plastic resin code of five, while bottles are code two. These types of plastic melt at different temperatures and require different levels of processing. They should be placed in appropriately marked containers before recycling.
Some newer recycling equipment eliminates the need for sorting recyclables by type and plastic resin code. Trucks drop various recyclables onto the floor and weed out large objects. The rest is fed through a drum that distributes the items on a conveyor belt, where workers remove plastic bags and coat hangers. The items are sent through star screens that remove corrugated cardboard. Workers again assess the items.
Recyclables are then sent through areas that sort out glass, magnetic metal, and aluminum. An infrared laser is shined on the remaining plastic to determine their resin codes. They are pushed by forced air into separate bins. Sorted recyclables are crushed into one ton bales. Remaining items are placed in landfill.
A plastic resin code is a number that indicates a type of plastic. All plastic is marked with this code; it appears on items as a number within a triangle. There are seven plastic resin codes. Polyethylene terephthalate, high-density polyethylene, polyvinyl chloride, and low-density polyethylene make up codes one through four. Polypropylene and polystyrene are codes five and six, and code seven is reserved for other resins.