Spring 2025

The Promise of Advanced Recycling

By Jessie Kneeland, Ph.D.

Recycling plastics is not easy, and most plastics produced are not recycled.  According to a recent report from the Organisation for Economic Co-operation and Development (OECD), out of 460 million metric tons of plastic produced worldwide in 2019, only 9 percent was recycled, 19 percent was incinerated, and the rest was disposed of in landfills or released into the environment (OECD, 2022).  In the United States (US) specifically, the numbers are similar.  Of the 35.7 million tons of US plastics generated in 2018, 8.7 percent was recycled, though the recycling rates are closer to 30 percent for certain types of plastics, including polyethylene terephthalate (PET) and high-density polyethylene (HDPE) bottles (US EPA, 2019).

According to a recent report from the Organisation for Economic Co-operation and Development (OECD), out of 460 million metric tons of plastic produced worldwide in 2019, only 9 percent was recycled, 19 percent was incinerated, and the rest was disposed of in landfills or released into the environment.”

Traditionally, plastic recycling has relied on mechanically grinding up plastic goods into smaller particles, then remelting those particles into a resin that can form new plastic goods.  Traditional recycling works well for plastic bottles and some packaging materials, though this process is not effective for all types of plastic materials.  Thus, some plastic materials are incinerated, reclaiming the plastic material as an energy source and preventing it from being landfilled or from leaking into the environment; however, incineration is a source of carbon dioxide emissions.

Plastics can be broken down chemically and used as fuel or feedstock.  This chemical process of breaking down plastic polymers for reuse is called “advanced recycling” or “chemical recycling” (OECD, 2022).  The two main processes that make up advanced recycling are thermolysis, which works on heterogeneous polymers (i.e., those composed of multiple monomer types), and chemolysis (also called “solvolysis”), which breaks down polymers composed of a single monomer.  “Thermolysis” is an umbrella term for multiple processes, but each of these processes results in breaking down a polymer into simpler, smaller molecular weight materials that can be used as fuels and solvents.  Some materials, such as polystyrene, PET, and polyvinyl chloride (PVC), are not suitable for thermolysis recycling due to the production of unwanted byproducts (NIST, 2024).  Chemolysis describes various chemical reactions that pull the polymer apart into individual monomer building blocks, which can be rebuilt from the ground up into new polymers.  Furthermore, solvent-based recycling is used to dissolve polymer molecules, remove impurities, and then precipitate the polymers into a new product without breaking apart the molecules (NIST, 2024).  In that sense, solvent-based recycling is similar to traditional mechanical recycling but with the added benefit of a higher purity product.

Advanced Recycling Processes and Outputs

There are several challenges with advanced recycling.  One major challenge for all types of plastic recycling is the cost involved in collecting and sorting plastic materials prior to recycling (NIST, 2024).  Plastic materials must be sorted first into different polymer types, and film-type plastics, such as plastic bags, can contaminate the recyclables and interfere with sorting equipment.  In addition, there are many impurities present in plastic materials being recycled – that delicious strawberry flavor in your yogurt and the colorful ink on the outside of the yogurt tub are no longer desirable when it comes time to recycle that plastic container.  Moreover, due to the costs to sort and process plastics, recycled plastics tend to be more expensive than the same materials made from virgin feedstock (NIST, 2024).  Another challenge of advanced recycling is the energy required, as advanced recycling uses more energy than traditional mechanical recycling (NIST, 2024).  The difference in energy and cost between traditional and advanced recycling depends on the specific chemical recycling technology, which is difficult to estimate for many newer chemical recycling methods (NIST, 2024).

On the other hand, there are some important benefits from plastic recycling.  Chiefly, recycling plastic reclaims plastic materials that might otherwise be landfilled and reduces the amount of raw petroleum-based feedstock needed to produce new plastic goods.  Plastic recycling also reduces carbon dioxide (CO₂) emissions compared to manufacturing plastic goods from primary resin (NIST, 2024).  Although the environmental benefits of advanced recycling are not as great as for mechanical recycling, advanced recycling can be used more times on the same material.  When combined with mechanical recycling, advanced recycling can add to the total amount of plastics diverted from the landfill and keep these plastics in economic use for longer.

Advanced recycling technologies exist in varying degrees of technological readiness, but capacity in pilot plants and commercial facilities is growing in the US (NIST, 2024).  As that capacity grows, the economies of scale will make advanced recycling increasingly profitable, though the economic viability of plastic recycling will continue to be determined by the price of petroleum.  Ultimately, greater implementation of chemical recycling will depend on policy and consumer demand for recycled plastics.