CRISPR for Editing Polymers Could Reshape Global Recycling Efforts

Unlocking Plastic Recycling

Since their widespread adoption by the manufacturing industry in the 1960s, plastics have become an omnipresent material in our daily lives. They are also the cause of very serious pollution, especially microplastics – the broken down, microscopic fragments of plastic polluting the entirety of the Earth and its oceans.

Microplastics have been demonstrated to reduce the effectiveness of antibiotics, to be found in fetuses, our hearts and brains, being eaten by marine fauna, etc.

There are many strategies being explored to deal with the already existing microplastic pollution, for example, adopting sustainability metrics, using non-toxic water-repelling solvents, or re-purposing plastics with lasers or light-driven photocatalysis.

Meanwhile, companies like ExxonMobil are being sued due to the low recycling rate of plastic produced with oil.

The problem with most solutions to plastic pollution is that they are somewhat costly, leading to many countries not being willing or able to implement solutions to what is a globalized problem. A better solution would be to make plastic waste a resource to produce valuable material, creating a strong economic incentive for plastic waste to be collected.

This is what researchers at Oak Ridge National Laboratory have been working on. They discovered a way to “upcycle plastic waste into higher-performance plastics”, publishing their results in the Journal of the American Chemical Society under the title “Polyalkenamers as Drop-In Additives for Ring-Opening Metathesis Polymerization: A Promising Upcycling Paradigm”¹.

Why Is Traditional Recycling Not Enough?

Plastic is already recycled, but the process is far from perfect. The researchers who worked on this publication describe it accurately as “melt and hope for the best”.

This is an issue, as each cycle of plastic recycling creates less and less valuable polymers, with the resulting product displaying inferior resistance, color, durability, etc. This happens because un-directed melting changes the way the plastic polymer chains are made and linked to each other.

So with current recycling technology, plastics can be reused only a limited number of times but will end up trash anyway, just after a few recycling cycles instead of a single use.

In addition, some types of plastics cannot really be recycled with this method at all, and generally end up either incinerated or in landfills.

In fact, only 9% of the global plastic production is recycled.

Source: PureCycle Technologies

Upcycling Instead of Recycling

The concept of “upcycling” is that the resulting product of the recycling process is actually superior to the initial material.

This can only be achieved by rearranging in a controlled fashion the polymer chains that form the plastic. This sort of precisely targeted “editing” of the plastic structure has led the researchers to compare their new method to CRISPR, a technology used to modify at will DNA and RNA strands.

They worked with molecules poorly or not at all recycled today. This included soft polybutadiene, a common material in rubber tires, and tough acrylonitrile butadiene styrene, used in plastic toys, computer keyboards, ventilation pipes, protective headgear, vehicle trims and molding, and kitchen appliances.

“We're addressing a significant component of the waste stream with this technology. That'd make a pretty big impact just from conservation of mass and energy from materials that are now going into landfills.”

Jeffrey Foster, Alvin M. Weinberg Distinguished Staff Fellow

The process has a very high “atom economy”, meaning that it recovers in the final product almost all the plastic to recycle that goes in.

How It Works

In order to recreate strong plastic polymers from material to recycle, they first created an additive to add to the existing plastic.

Source: Journal of the American Chemical Society

To make the additive, they shredded polybutadiene and acrylonitrile butadiene styrene and immersed it in dichloromethane. The chemical reaction worked at low temperatures (40°C / 104°F) and in less than two hours.

The reaction also needed a catalyst, and ruthenium was used. This is a well-known catalyst in plastic manufacturing and is also used to convert biomass, such as plant oils, into fuels and other high-value organic compounds.

The ruthenium atoms are essentially “carrying” the smaller plastic elements and bringing them to the polymers to make them longer.

The “metathesis” process uses strong double bonds between carbon atoms to increase the chances of chemical reactions.

One part of the method, called ring-opening metathesis polymerization, opens circular carbon molecules and turns them into useful long polymers. Another part, called cross-metathesis, inserts chains of polymer sub-units from one polymer chain into another.

Source: Sigma Aldrich

The work was a collaborative task, with some researchers tasked with optimizing polymerization, others using NMR (nuclear magnetic resonance) spectroscopy to analyze the reactions in real time, and others testing the mechanical and thermal properties of final materials.

Strong Results

The Oak Ridge National Laboratory scientists demonstrated that the process, which uses less energy and produces fewer emissions than traditional recycling, efficiently integrates waste materials without compromising polymer quality.

The resulting upcycled plastic displayed strong thermal and mechanical performance, making it superior to the original material, and much superior to plastic recycled with traditional methods.

The Next Steps In Plastic Upcycling

Upcycling All Plastics

This method, now demonstrated for certain plastics, could be expanded to all other plastics. More environment-friendly solvents could be an improvement as well.

“The vision is that this concept could be extended to any polymer that has some sort of backbone functional group to react with.

If scaled up and expanded to employ other additives, broader classes of waste could be mined for molecular building blocks, dramatically reducing the environmental impact of other difficult-to-process plastics.”

Jeffrey Foster, Alvin M. Weinberg Distinguished Staff Fellow

The details of the procedure’s economics also need to be clarified, but it should be okay as it uses low temperature, short reaction time, and a commonly used catalyst.

Beyond Plastics

The method used worked with plastics but could be deployed to other chemicals as well.

The researchers see it as especially promising for a class of polymer material called thermoset. This includes epoxy resins, vulcanized rubber, polyurethane, and silicone.

Thermoset materials cannot be remelted or reshaped once set, which makes their recycling a challenge.

The upcycling method developed here, attacking the cross-linked molecular structure of plastics, could be applied to the same structure in thermoset materials.

Because the repolymerization process is highly customizable, the final upcycled product could be superior to the original. The upcycled materials might be, for instance, softer and stretchier than the original polymers or, perhaps, easier to shape and harden into durable thermoset products.

Conclusion

Upcycling is a promising option to boost the rate of plastic recycling, as it should provide the economic incentive that was missing until now to get more than 10% of plastic recycled globally.

Reducing plastic usage, removing microplastics, developing bioplastics (see “Top 5 Bioplastics Companies“), and upcycling instead of poor recycling are likely all going to be part of the solution to plastic pollution.

Altogether, they will be a key component in developing a circular economy that is much more resource-intensive and much less polluting.

Recycling Company

PureCycle Technologies

PureCycle is a plastic recycling company focused on polypropylene (PP), turning waste PP into ultra-pure recycled PP resin.

They have created a proprietary procedure to “clean” the waste PP from all the added material in finished products, like polyethylene, solid material, pigments, contaminants, etc.

Source: PureCycle Technologies

This extraction process differs from the commonly used mechanical filtration system, which generates too low-quality PP for most industrial applications, even when using high-quality feedstock.

Chemical recycling is another option, but it is far from environmentally friendly and is not cost-efficient.

Source: PureCycle Technologies

Purecycle's final product is accepted by the FDA for various PP usual applications, including food storage, hot or pasteurized containers, and frozen food storage. Future products should include fiber, film packaging, injection mold for packaging, and automotive plastics.

In addition to recycling waste plastic, the process is a lot more energy efficient with 79% lower than consumption for “virgin PP”, and a 35% lower greenhouse gas emission footprint.

The company has been building its Ironton pellet production facility, with the first production in June 2023, to deploy its recycling process.

It is also building other facilities in North America and Europe, and later on planned in Japan and South Korea with a joint-venture with SK geo centric, aiming to reach 630 million pounds of annual recycling capacity to be reached in 2027

Source: PureCycle Technologies

The Ironton facility pellet production reached 3.5 million pounds in Q3 2024, tripling from the quarter before, as well as seeing an increase in the resulting product quality.

Overall, PureCycle is a good company to bet on improving plastic recycling technology, and with the experience to progressively deploy new technology moving away from legacy recycling technology.

Study Reference:

^{1. Jeffrey C. Foster, et al. (2024) Polyalkenamers as Drop-In Additives for Ring-Opening Metathesis Polymerization: A Promising Upcycling Paradigm. Journal of the American Chemical Society 2024 146 (48), 33084-33092 DOI: 10.1021/jacs.4c10588}