The plastic waste we produce is making our planet and all life on it sag under its weight. We need to find new ways to deal with these non-biodegradable substances that are thrown away after they have been used.
A new study has shown that a new method of plastic recycling is possible. It was inspired by nature's natural'recycling' of the organic polymers found in our environment.
This approach is based on the fact that organic polymers proteins are continually broken down into smaller pieces and reassembled to make new proteins. However, the quality of the building blocks does not change. When it comes to recycling plastic, a synthetic polymer, without it degrading, it is important to think smaller.
Proteins are the most important organic compounds, and they act as building blocks of everything biological. These long chains of molecules, also known as monomers, are called amino acids. Researchers believe that the way they can be broken down and reconfigured could lead to a strategy for recycling synthetic polymers.
Simone Giaveri (materials scientist at the cole polytechnique fdrale de Lausanne, EPFL in Switzerland) says that a protein is like a string made of pearls. Each pearl is an amino acids.
Each pearl is unique and each pearl has its own color. The string structure and properties of each pearl are determined by the sequence of their colors. Nature's protein chains are broken down into their constituent amino acids. Cells then put these amino acids back together to create new proteins.
Researchers have named their approach "nature inspired circular-economy recycle", or NaCRe.
The team was able, in lab tests, to separate selected proteins into amino acid, and then assemble them into proteins with different structures. One case involved turning silk proteins into green fluorescent protein. This is a tracer that can be used in biomedical research. Despite all the deconstruction and reconstruction, the quality remains the same.
(Giaveri et al., Advanced Materials, 2021)
The team found that the same mechanisms that are naturally found in proteins can be applied to plastics, but it will take time to develop and scale up the technology.
Although there are many differences between synthetic and natural polymers, researchers believe this new method of recycling is possible and will keep materials in service for as long as possible.
Francesco Stellacci from EPFL, a materials scientist, says that it will require a completely different mindset. "Polymers are strings made of pearls. Synthetic polymers, however, are mostly made of pearls of the same color. The sequence of colors is rarely important when there are many pearls."
"Furthermore we don't have a method to efficiently assemble synthetic polymers of different colors pearls in a manner that controls their order."
Even biodegradable plastics can create waste residue, which must be stored or buried once the recycling process has finished. This will have the usual impact on the environment in terms land use and pollution. This could be fixed by the new strategy.
Researchers estimate that over a lifetime of 70 years, an average person will throw away approximately 2 metric tons of plastic. This is a huge amount considering that there are almost 8 billion people on Earth right now.
While we are making progress towards tackling the plastic pollution problem, it is not enough. If we want to stop plastics from causing further harm to our environment and our health, it will take a radical shift in our thinking and actions.
Stellacci says that sustainability will require upcycling, which means combining a variety of objects and recycling them to create new materials every day. Nature already does this."
The research was published in Advanced Materials.