Revolutionary Eco-friendly, infinitely recyclable PDK plastic has been developed by Berekely Labs

Plastics are a part of nearly every product we use on a daily basis. And with a lot of use, comes a lot of waste, and plastic is very harmful to all the life forms on Earth.

A team led by Corinne Scown, Brett Helms, Jay Keasling, and Kristin Persson at Lawrence Berkeley National Laboratory (Berkeley Lab) set out to change that. 

Less than two years ago, Helms announced the invention of a new plastic that could tackle the waste crisis head-on. Called poly(diketoenamine), or PDK, the material has all the convenient properties of traditional plastics while avoiding the environmental pitfalls, because, unlike traditional plastics, PDKs can be recycled indefinitely with no loss in quality. 

 The team has released a study that shows what can be accomplished if the manufacturers began using PDKs on large scale, in which a simulation for a 20,000-metric-ton-per-year facility that puts out new PDKs and takes in used PDK waste for recycling, then calculated the chemical inputs, technology needed, greenhouse gas emissions, then compared their findings to the equivalent figures of production of conventional plastics. 

“These days, there is a huge push for adopting circular economy practices in the industry. Everyone is trying to recycle whatever they’re putting out in the market,” said Nemi Vora, the first author on the report. “We started talking to industry about deploying 100% infinitely recycled plastics and have received a lot of interest.”

“The questions are how much it will cost, what the impact on energy use and emissions will be, and how to get there from where we are today,” added Helms, a staff scientist at Berkeley Lab’s Molecular Foundry. “The next phase of our collaboration is to answer these questions.”

To date, more than 8.3 billion metric tons of plastic material have been produced, and the vast majority of this has ended up in landfills or waste incineration plants. Out of which only a small proportion of plastics are recycled, where they are remelted and then re-shaped into new products. But this technique has its limited benefits as the plastic resin is made from polymers, long chains of monomers, and to give plastic its texture, colors, and capabilities, additives like pigments, heat stabilizers, and flame retardants are added. And when many plastics are melted together, polymers get mixed with their multiple additives, which results in a material with lower quality. As such, less than 10% of plastic is mechanically recycled more than once, and recycled plastic usually also contains virgin resin to make up for the dip in quality.

Whereas in PDK plastics, the resin polymers are engineered to easily break down into monomers when mixed with an acid, after which monomers can be separated from any additives and gathered to make new plastics without any loss of quality. The team’s earlier research shows that this “chemical recycling” process is light on energy and carbon dioxide emissions, and it can be repeated indefinitely, creating a completely circular material lifecycle where there is currently a one-way ticket to waste.

Credit: Peter Christensen/Berkeley Lab

The PDKs need to be convenient to replace traditional plastic, as they have to compete with virgin resin as creating virgin resin is very easy and cheap. “And the main takeaways were that, once you’ve produced the PDK initially and you’ve got it in the system, the cost and the greenhouse gas emissions associated with continuing to recycle it back to monomers and make new products could be lower than, or at least on par with, many conventional polymers,” said Scown.

Planning to launch

Thanks to optimization from process modeling, recycled PDKs are already drawing interest from companies needing to source plastic. Always looking to the future, Helms and his colleagues have been conducting market research and meeting with people from the industry since the project’s early days. Their legwork shows that the best initial application for PDKs are markets where the manufacturer will receive their product back at the end of its lifespan, such as the automobile industry (through trade-ins and take-backs) and consumer electronics (through e-waste programs). These companies will then be able to reap the benefits of 100% recyclable PDKs in their product: sustainable branding and long-term savings.

“With PDKs, now people in industry have a choice,” said Helms. “We’re bringing in partners who are building circularity into their product lines and manufacturing capabilities, and giving them an option that is in line with future best practices.”

Added Scown: “We know there’s interest at that level. Some countries have plans to charge hefty fees on plastic products that rely on non-recycled material. That shift will provide a strong financial incentive to move away from utilizing virgin resins and should drive a lot of demand for recycled plastics.”

After infiltrating the market for durable products like cars and electronics, the team hopes to expand PDKs into shorter-lived, single-use goods such as packaging.

A full-circle future

As they forge plans for a commercial launch, the scientists are also continuing their techno-economic collaboration on the PDK production process. Although the cost of recycled PDK is already projected to be competitively low, the scientists are working on additional refinements to lower the cost of virgin PDK, so that companies are not deterred by the initial investment price.

And true to form, the scientists are working two steps ahead at the same time. Scown, who is also vice president for Life-cycle, Economics & Agronomy at the Joint BioEnergy Institute (JBEI), and Helms are collaborating with Jay Keasling, a leading synthetic biologist at Berkeley Lab and UC Berkeley and CEO of JBEI, to design a process for producing PDK polymers using microbe-made precursor ingredients. The process currently uses industrial chemicals but was initially designed with Keasling’s microbes in mind, thanks to a serendipitous cross-disciplinary seminar.

“Shortly before we started the PDK project, I was in a seminar where Jay was describing all the molecules that they could make at JBEI with their engineered microbes,” said Helms. “And I got very excited because I saw that some of those molecules were things that we put in PDKs. Jay and I had a few chats, and we realized that nearly the entire polymer could be made using plant material fermented by engineered microbes.”

“In the future, we’re going to bring in that biological component, meaning that we can begin to understand the impacts of transitioning from conventional feedstocks to unique and possibly advantaged bio-based feedstocks that might be more sustainable long term on the basis of energy, carbon, or water intensity of production and recycling,” Helms continued.

“So, where we are now, this is the first step of many, and I think we have a really long runway in front of us, which is exciting.”

Source: Berkeley Lab