塑料循环利用有四种形式：初级循环，即塑料重新用于相同用途；二级循环，即（被混合或受污染的）材料用于要求较低的用途；三级循环，即用回收塑料提炼单体和化学物质；四级循环，即焚烧并利用从中产生的能量。
There are four categories of plastics recycling: primary recycling, in which the plastic is re-used in the same application; secondary recycling, in which material (mixed or contaminated) is used in less demanding applications; tertiary recycling, in which the plastic is converted into monomers or chemicals; and quaternary recycling, in which only energy is recovered through incineration.