Screw Caps Alternative ways to recycle Put in Recycling Cart/Bin Remove metal screw caps from bottles and jars so that they can be sorted separately. Plastic caps should stay attached to their plastic bottles for recycling. Plastic caps from paper cartons (such as milk cartons) or tetrapaks should go in the garbage cart because they are made from a different material from the package. Plastic Caps Are Different Plastic caps have separate disposal instructions. Find out how to dispose of plastic caps. Recycle Metal Jar Lids Metal jar lids greater than 2-3 inches in diameter can be recycled. Make sure they are separated from their jars so they can be sorted correctly. Alternative Ways to Recycle Metal Screwcaps Are Scrap Metal Metal screw caps can be collected and recycled with other scrap metal. Simply separate aluminum caps (non-magnetic) from steel caps (magnetic).