The method for recycling different types of plastic depends on local municipal regulations; some municipalities accept all types of plastic, while others accept only plastic containers and other items with certain numbers stamped on their bottoms. As of 2015, there are seven basic types of plastics, generally designated by a number from one to seven surrounded by a triangle of arrows.
The Society of the Plastics Industry developed the numerical coding system in 1988 to make it easier for consumers and recyclers to identify the various types.
Virtually all municipalities and recycling stations accept type 1 plastics. Made from polyethylene terephthalate, type 1 plastics are the most common and easiest to recycle of all the plastics. Type 2 high-density polyethylene plastics, which include heavier containers used to hold milk, shampoo, motor oil, detergents and other liquids, are also quite easy to recycle and are widely accepted by most recycling facilities. Type 6 polystyrene or Styrofoam plastics are also commonly accepted, although some recycling facilities have separate recycling bins for this type.
Few recycling centers accept type 3 polyvinyl chloride plastics, type 4 low-density polyethylene plastics or type 5 polypropylene plastics, as these have a very low rate of recyclability. Type 7 plastics, made from a combination of other plastics, are generally the most difficult type of plastic to recycle and are very rarely accepted by recycling centers.