How is recycling of plastics beneficial to the climate?

Question

How is recycling of plastics beneficial to the climate? Using PET flakes, for example, reduces your indirect demand for oil extraction, it's good. But if you break them down to monomers during chemical recycling, it's more or less the same thing as synthesizing monomers from oil or gas, isn't it? Is reducing demand for oil the only reason production with recycled material has a lower carbon footprint than virgin production? Are there complex analyses that look into when (at what stages) GHGs are emitted and what technological differences between recycled and virgin plastics lead to different climate impacts?

Answer 1

Recycling plastic uses less energy than producing new plastic

Note: this answer borrows heavily from my answer to an earlier question about shipping plastic.

According to Wikipedia, polyethylene (PE) is the most common type of plastic. There are three main categories of polyethylene (also from Wikipedia):

• PET (polyethylene terephthalate), used in polyester fibers, drink bottles, tote bags, furniture, etc.
• HDPE (High-density polyethylene), used in bottles, playground equipment, plastic lumber, etc.
• PP (polypropylene), used for auto parts, industrial fibers, food containers, and dishes.

In 2019 the American Chemistry Council (ACC), the Association of Postconsumer Plastic Recyclers (APR), the National Association for PET Container Resources (NAPCOR), and the PET Resin Association (PETRA) funded a third-party life cycle analysis of PET, HDPE, and PP recycling. The study is available here (pdf): "Life Cycle Impacts for Postconsumer Recycled Resins: PET, HDPE, and PP".

The results show significant energy savings from using recycled plastics:

The analysis includes all aspects of the recycling process, including collection, transportation, cleaning, and processing. "Cut-off" assigns 100% of the impacts of the virgin plastic to the first use, while the "open loop" analysis distributes the impact of the virgin plastic across all subsequent uses of the product (i.e. even a product made from 100% recycled plastic required virgin plastic at some point in it's lifecycle).

For the sustainability-minded, the open loop analysis is most relevant -- in this case, recycling PE results in an energy savings of about 30% compared to virgin PE.