Engineers introduce a new approach for recycling plastics

Date:
September 23, 2021
Source:
Ecole Polytechnique Fe'de'rale de Lausanne
Summary:
Engineers have come up with a revolutionary new method for tackling
plastic pollution by harnessing the inner workings of proteins. The
result? A whole new way of looking at plastic recycling.



FULL STORY ==========================================================================
Each human being uses, on average, 30 kg of plastic per year. Given
that global life expectancy currently stands at approximately 70 years,
each person will discard some two metric tons of plastic in his or her lifetime. Multiply that by the number people on earth -- which is growing constantly -- and the total is staggering. In light of this, Francesco Stellacci, a full professor and head of the Supramolecular Nanomaterials
and Interfaces Laboratory at EPFL's School of Engineering, began thinking
about whether there was a way to solve the problem of used plastics and
recycle it more effectively. Stellacci established a collaboration with
Prof. Sebastian J. Maerkl in the Bioengineering Institute at EPFL and they decided to co-advise a PhD student, Simone Giaveri, the team has published
its conclusions, based on scientific research, in Advanced Materials.


========================================================================== After reviewing the existing plastic-recycling options available, the
engineers decided to think up a completely new approach. "When we use biodegradable plastics, the degradation process leaves residue that
must be stockpiled or buried. The more land that is allocated for this
means the less land available for farming, and there are environmental consequences to take into account as bio-degradation product necessarily
change the area's ecosystem," says Stellacci. So how can we come up with
a comprehensive solution to the problem of recycling plastics? Part of
the answer could very well come from nature itself.

A pearl necklace Proteins are one of the main organic compounds of which
our world is made of.

Like DNA, they form part of the family of polymers; proteins are long
chains of molecules, or monomers, known as amino acids. "A protein is
like a string of pearls, where each pearl is an amino acid. Each pearl
has a different colour, and the colour-sequence determines the string
structure and consequently its properties. In nature, protein chains break
up into the constituents amino acids and cells put such amino acids back together to form new proteins, that is they create new strings of pearls
with a different colour sequence" Giaveri says.

In the lab, Giaveri initially attempted to replicate this natural cycle, outside living organisms. "We selected proteins and divided them up into
amino acids. We then put the amino acids into a cell-free biological
system, that assembled the amino acids back into new proteins with
entirely different structures and applications," he explains. For
instance, Giaveri and Stellacci successfully transformed silk into a
protein used in biomedical technology.

"Importantly, when you break down and assemble proteins in this way,
the quality of the proteins produced is exactly the same of that of
a newly synthesized protein. Indeed, you are building something new,"
Stellacci says.

Plastic is a polymer, too So what's the connection between protein
assembly and plastic recycling? Because both compounds are polymers,
the mechanisms naturally occurring in proteins could be applied to
plastics as well. While this analogy may sound promising, Stellacci
warns that developing such methods won't happen overnight.

"It will require a radically different mindset. Polymers are strings
of pearls, but synthetic polymers are made mostly of pearls all of the
same colour and when the colour is different the sequence of colour
rarely matters.

Furthermore, we have no efficient way to assemble synthetic polymers from different colour pearls in a way that controls their sequence." He would
also point out, however, that this new approach to plastic recycling
appears to be the only one that truly adheres to the postulate of a
circular economy. "In the future, sustainability will entail pushing
upcycling to the extreme, throwing a lot of different object together
and recycling the mixture to produce every day a different new
material. Nature already does this," he concludes.

========================================================================== Story Source: Materials provided by
Ecole_Polytechnique_Fe'de'rale_de_Lausanne. Original written by Vale'rie Geneux. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Simone Giaveri, Adeline Marie Schmitt, Laura Roset Julia`, Vincenzo
Scamarcio, Anna Murello, Shiyu Cheng, Laure Menin, Daniel Ortiz,
Luc Patiny, Sreenath Bolisetty, Raffaele Mezzenga, Sebastian Josef
Maerkl, Francesco Stellacci. Nature-Inspired Circular-Economy
Recycling for Proteins: Proof of Concept. Advanced Materials,
2021 DOI: 10.1002/ adma.202104581 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210923122410.htm

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