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Our planet and everything that lives on it is crumbling under the weight of all the plastic waste we produce. The volume of these non-biodegradable materials discarded after use is only increasing, so we need new ways to combat them, and quickly.
New study demonstrates proof of concept of a whole new approach to plastic recycling, inspired by how nature naturally “recycles” organic polymer components found in our environment.
The approach is inspired by the fact that proteins contained in organic polymers are constantly broken down into parts and reassembled into different proteins, without losing the quality of the building blocks. In essence, when it comes to recycling plastic – a synthetic polymer – without breaking it down, we have to think smaller.
Proteins are one of the main organic compounds that act as the building blocks of all things biological. They are long chains of molecules (or monomers) called amino acids, and researchers believe the way these molecules can be broken down and reconfigured suggests a potential strategy for recycling synthetic polymers.
“A protein is like a string of pearls, where each pearl is an amino acid,” explains Simone Giaveri, materials scientist at the Federal Polytechnic School of Lausanne (EPFL) in Switzerland.
“Each bead has a different color, and the sequence of colors determines the structure of the string and therefore its properties. In nature, protein chains break down into constituent amino acids, and cells put these amino acids together to form new proteins – that is, they create new pearl necklaces with a different color sequence. “
The researchers called their approach ‘recycling in a nature-inspired circular economy’, or NaCRe for short.
In lab tests, the team was able to split selected proteins into amino acids and then assemble them into new proteins with different structures and uses. In one case, they turned silk proteins into green fluorescent protein, which is a bright tracer used in biomedical research. Despite this deconstruction and reconstruction, the quality of the proteins remains constant.
(Giaveri et al., Advanced materials, 2021)
According to the team’s analysis, the mechanisms that occur naturally in proteins could also be applied to plastics, although the development and scale-up of the necessary technology will take some time.
There are major differences between natural and synthetic polymers to be aware of, but the researchers say this new approach to recycling is achievable – and would keep used materials for as long as possible.
“It will require a radically different mindset,” explains materials scientist Francesco Stellacci of EPFL. “Polymers are strings of pearls, but synthetic polymers are mostly made of pearls all of the same color and when the color is different, the color sequence rarely matters.”
“Furthermore, we have no efficient way of assembling synthetic polymers from beads of different colors in such a way as to control their sequence.”
Even biodegradable plastics create waste residue that must be stored or buried after the recycling process is complete, with the usual ripple effects on the environment in terms of land use and pollution. The new strategy could help solve this problem.
Researchers estimate that over a 70-year lifespan, an average person throws away about 2 metric tons of plastic – and given that almost 8 billion people currently live on the planet, that’s an amount catastrophic waste.
And while we are making progress in tackling our plastic pollution problem, it is currently nowhere near enough. A radical shift in thinking and action is needed if we are to stop plastics from further damaging our world and our health.
“In the future, sustainability will mean taking upcycling to extremes, throwing a lot of different objects together and recycling the mixture to produce a new, different material every day,” says Stellacci. “Nature already does that.”
The research was published in Advanced materials.
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