Polystyrene – Characteristics of a Renewable Resource
Single-use polystyrene has been a focus of bans in certain cities and states throughout the US in the last couple years. We want to provide a resource page citing updates and progress on the recyclability of polystyrene in the World. These bans are creating a negative name for polystyrene, but the reality is new research is showing polystyrene is one of the most valuable polymers in circulation. We need to take advantage of this resource, not ban it. Polystyrene is not a recycling problem, it’s a littering and collection problem.
Two Types of Polystyrene Recycling
The first type of polystyrene recycling is a more traditional method that has been done for many years. Our company, for example, has been doing it for over 40 years. This type of recycling is called mechanical recycling, where a foam product is mechanically chopped into fine pieces, melted down, cooled, and re-pelletized into a recycled polystyrene pellet. These pellets can then be put back into a new foam product, completing the circularity of polystyrene recycling. We are able to mechanically recycle 97% of our scrap foam year after year. Our foam scrap is known as post-industrial plastic meaning it was the result of us processing a finished part, but it never reached a consumer. Capturing and recycling this material is easy because it never leaves our site. The other type of foam scrap is called post-consumer scrap, where it reached the consumer and was used. Collection of post-consumer scrap has been the challenge for polystyrene in the past and mostly because municipalities haven’t forced it to be part of state or local curbside recycling programs. Concerns on the financial value of a collected piece of foam versus the costs to collect, sort, and reprocess has been a main underlying reason why. A recent study in early 2020 said that polystyrene is shown to be one of the most sortable plastics in the waste stream. The study stated that “styrenic compounds have a unique signal that make it easy to identify specific properties of the material that results in very precise sorting, an advantage that some of the other polymers do not have.”* A link to the study can be found below in the Important Milestones and Resources section. If the sorting is figured out, breakthrough technology we’ll explain below has the reprocessing figured out, all that is left is the creation of curbside collection for polystyrene to figure out.
The second type of recycling technology was introduced commercially in 2018 and is known as depolymerization. Depolymerization is a type of chemical recycling that breaks polystyrene down into a liquid that increases the ease of purification. The purified liquid monomer can then be processed back into a virgin pellet, completing the circularity of polystyrene recycling. This process has been successfully completed at full truckload scale. This technology is a breakthrough for the material and for plastics recycling as an industry. Polystyrene is one of the top plastics that can be chemically recycled due to these advantages:
- It is the polymer that can be most easily reversed to its original monomer
- It can be chemically reversed to only one monomer at a very high yield
- Its monomer is a liquid, which enables easy purification compared to solid or gaseous monomers
The monomer form of recycled polystyrene is identical to that of a virgin monomer. This is key and allows it to be processed into a virgin resin that can continuously be chemically recycled an infinite amount of times without quality or purity degradation.
The definition of a renewable resource is a resource which can be used repeatedly and replaced naturally. Polystyrene has the used repeatedly portion of this down thanks to chemically recycling capabilities. It’s time we start viewing polystyrene as a valuable resource, rather than waste that needs to go to a landfill. “Scrap” or “waste” is not an end product but rather part of the life cycle of a material.
The Solution – Collection Instead of Banning
This is where the efforts need to be made. We’ve established that PS is one of the top plastics available for both Chemical and Mechanical Recycling. The focus needs to be on collecting this valuable resource, not banning its existence.
Important Milestones and Resources