Unexpected Ways to Repurpose Plastics

Note: I’m a student researching the root causes behind the issue of plastic pollution in the hopes of figuring out the key roadblocks in the way we solve this challenge! My team is exploring many different areas of this enormous problem and I’m writing this series of articles about our key findings. If you find this interesting and would like to see some of our other research, feel free to check out our work at theplasticshift.com

When it comes to recycling plastics, we can easily imagine the stereotypical scene: walking out to the curbside, putting the recycling in a bin, and having it picked up by a friendly neighbourhood garbage truck. Yet, this is only the tip of the iceberg when it comes to all the work it takes to recycle our waste.

For one, there’s also the next step of the garbage trucks taking these plastics to recycling facilities where they’re processed. This means sorting plastics by polymer type, cleaning contaminants such as food residue from them, etc. By some estimates, up to 25% of waste that ends up at a recycling facility is sent to the landfill because of contamination (Source). Even so… this part of the process isn’t where the plastics are actually RECYCLED.

Workers in the Recycling Center at the Shady Grove Transfer Station‎, Montgomery County, Maryland (Source)

The processing of plastics is just a precursor to the actual process by which plastics are recycled — which involves melting them down at specific temperatures so that they can be remoulded into new products. This presents several challenges in the recyclability of plastics, since some plastic polymers lose quality when melted or can contaminate batches of plastic (Source). This is something that the general public is less aware about.

By some estimates, up to 80% of plastics have low residual value — meaning they lose quality when they are recycled by being melted into new products (Source). Thus, this lesser-known part of the recycling process is actually crucial when it comes to how much of our waste can be recycled. Now, it is important to acknowledge that not all players in this industry are affected the same way by the amount of plastic they collect that has low residual value (Source), but it still is a major bottleneck in the industry.

So since many types of plastics are downgraded when recycled (or more specifically when melted down to form new products)… what if there were ways to get around this problem by recycling plastics without the need for melting them down?

Let’s Enter the World of “Alternative Recycling”

Or instead of ‘alternative recycling’ — let’s say ‘repurposing’. When it comes to the key idea behind recycling, it’s that we shouldn’t just take useful material and throw it away (causing negative economic, environmental, and social implications) (Source). Instead, we try to repurpose the waste we have into new useful products.

There are a number of solutions for this besides just melting plastics to form new products. Some of them have the potential to repurpose plastic waste (especially waste that has low residual value when it comes to melting it) to create urgently needed materials (mainly for construction).

Repurposing Plastics for Construction Materials

Although this might bring up pictures of children’s building blocks, this is a very serious solution when it comes to ways for repurposing plastic waste. When it comes to the construction industry, there have been many issues with rising prices (especially with housing) — in part due to increasing material costs (Source).

This sets a good stage for the search for cheaper construction materials. And when it comes to cheap construction materials, repurposing materials from waste instead of manufacturing new materials can be a way to reduce costs in some cases. This is where repurposing plastic waste for construction materials is prevalent (although not all construction materials made from plastic are manufactured without melting the plastics).

One common type of construction material made from repurposed plastic is plastic lumber. This is effectively a replacement for wooden planks, beams, etc. that is often a mix of plastic (like HDPE) and another composite material (like wood or fibreglass) (Source). This material is already widely in use in North America, where it can be applied to making items like flooring planks, railway ties, etc. (Source).

This plastic lumber has a few key advantages over regular wooden construction materials. For one, it’s more resilient because it is less affected by environmental factors (ex. weather, rotting, termites, etc.) than wood. Additionally, it has comparable structural strength/stability to typical construction materials and does not require maintenance such as repainting or restaining as frequently as other materials.

That being said, the production of plastic lumber requires relatively high initial infrastructure investments, high technical expertise, and the ability to sort plastics to ensure specific polymers are used in products (especially in developing countries). Also, plastic lumber production does involve melting plastics, although several plastic polymers can be mixed together when melted (which reduces the level of purity needed) (Source).

Another disadvantage is that for low size-to-volume plastics (ex. like thin LDPE plastic bags that don’t actually have a lot of material), a lot of collection is required to get the volume needed for producing these materials (although that’s common to most construction materials made from repurposed plastic). A more detailed cost/benefit analysis can be found here.

An example of a wood plastic composite (Source)

Another promising way to repurpose plastic is to create products like plastic bricks. These are less widespread than plastic lumber and are often credited to the work of a company called Conceptos Plasticos in Colombia (although there are also other versions of plastic bricks as a product). Their plastic bricks have similar advantages as plastic lumber, except that they don’t involve melting plastic waste.

Instead, the plastic waste of different polymers is ground into a fine powder. This is then combined in different proportions with additives to create plastic bricks which easily intersect with each other and are resistant to fires, earthquakes, etc. (Source). This makes the bricks lightweight and modular.

When it comes to the costs of creating these plastic bricks, one example in the Philippines put the price at about $0.40 USD (Source). This is good compared to North American standards, where bricks can cost between $0.50 to $0.75 (Source). In developing countries like the Philippines, however, there are more cost-effective bricks made from soil (Source). All things considered, plastic bricks need more development before they become a larger solution to repurposing plastic waste.

Another construction material made from repurposed plastic waste that is currently in the process of being developed is plastic pavement. Typically, roads use some amount of bitumen (a petroleum product) in their production (Source). So the idea is to be able to repurpose plastic waste as petroleum products that can replace materials in road pavement.

Essentially, plastic waste is recycled as it would be normally and eventually turned into pellets that can be remoulded into plastic pavement, along with materials like asphalt (note that the fabrication of plastic pavement still uses typical recycling processes such as melting. But again, there is less need for absolute purity in sorted polymers — like PET and PP).

Currently, this idea is mainly theoretical. There is a notable amount of research being done on the effectiveness of plastic pavement when it comes to performance factors like strength and durability (Source). Additional areas being studied are the exact composition of the pavement when it comes to the percentage of plastic vs. other materials (ex. sand).

There is also a startup working to launch pilot programs that use plastic pavement to manufacture roads (Source). It shows positive results from these programs, claiming that roads made from plastic pavement have 3x the lifetime of roads made from conventional materials and that the construction time of manufacturing a road should be reduced by 70% when using plastic pavement (due to it being prefabricated in modular components).

There are also many other construction materials made from repurposed plastic waste (like plastic roofing, plastic tiling, plastic insulation, etc.). These materials are not as widely implemented, but there is a more comprehensive overview here.

Repurposing Plastics for Consumer Products

Now construction materials aren’t the only alternatives to repurpose plastic waste. It could also be said that plastic waste could be repurposed into consumer products such as bracelets or decorations without the use of sorting and melting down the plastics into new products.

This isn’t common, however. Organisations that sell consumer products like bracelets made out of recycled plastics (ex. 4Ocean) typically use high residual value plastics (not part of the 80% that we have difficulty recycling). Although not all organisations melt down products to remould them (ex. Ocean Sole Africa carves plastic flip flops into decorative items), they still typically use high-residual value plastics.

So although theoretically, it is possible for low residual value plastic waste to be repurposed in alternative methods to create consumer products (ex. grinding down the plastics into smaller pellets and gluing them together — like with plastic bricks)… we haven’t yet seen any examples of this in practice.

This could be a promising approach to consider, however, because consumers aren’t as sensitive to the unit costs of these materials as industrial buyers (such as construction builders). An organisation working to repurpose low residual value plastic waste into consumer products might have an easier time scaling because they don’t have to compete with the costs of traditional recycled / non-recycled materials down to every cent.

On the whole, for all these alternative materials for repurposing plastics, there aren’t many examples where these solutions have been deployed at a large scale. While this work seems promising, it remains largely theoretical. But given how these new alternative materials have the potential to repurpose up to 80% of low residual value plastic waste and prevent it from ending up in landfills (or worse, open dumps), it’s important that we keep continuing to research and develop these materials.

Before You Go

Hey, if you found that article interesting, feel free to check out some of my other research at theplasticshift.com. If you have any questions or thoughts, feel free to get in touch with me via Linkedin.

Cofounder at The Plastic Shift. Learning how to create a sustainable planet. Linkedin: linkedin.com/in/madhav-malhotra/

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