It's no longer a secret that we have a problem with plastic waste.

However, it is equally obvious that life as we know it would not be possible without plastics.

In everyday life we ​​find them in packaging, in the house, in our clothes - but unfortunately also in our environment.

Because what happens to a plastic bottle in the ocean?

If nobody collects and disposes of it, it will float undisturbed for up to 450 years.

The robustness of the polymer materials is thus nature's undoing.

But even professional disposal does not completely solve the problem.

According to the Federal Environment Agency, just under half of our plastic waste was recycled in 2019.

So what could sustainable solutions to the plastic problem look like?

From a chemical point of view, a plastic consists of long molecular chains, so-called polymers, whereby the individual chain links usually come from the further processing of petroleum fractions.

Plastics based on biomass can also be found more and more frequently.

The properties of a plastic depend on the chain links used, the monomers.

The connection between them is usually so strong that polymers cannot be broken down again into the individual monomers.

A polymer that can be broken down into its individual parts would therefore be an ideal basis for a more sustainable plastics industry.

An American and a German research group have now independently been able to fulfill a further requirement for this.

New processes for recycling bio-based plastics

The chemists James Sternberg and Srikanth Pilla from the University of Clemson in South Carolina have presented a new process for recycling bio-based plastics in the journal "Nature Chemistry".

These are polyurethanes, which are mainly known from foamed plastics such as construction foam or sponges.

The raw material used is lignin, a biopolymer that is responsible for the lignification of plants and is produced in the manufacture of paper.

So far, all attempts to recycle such plastics have failed due to structural changes in the lignin, which made it unsuitable for further use.

The researchers have now succeeded in gently recovering up to 93 percent of the lignin.

The addition of ethylene glycol, a de-icing agent and component of PET plastics, plays a key role here.

New polyurethane can be produced from the recycled lignin, which shows only slight losses in mechanical strength compared to the original plastic.

The researchers are now working on scaling their method.

A group of chemists led by Stefan Mecking from Constance achieved a similar success.

They have synthesized a readily degradable polyester with properties similar to high density polyethylene (HDPE).

The latter is one of the most common plastics in the world and can be found in foils and shampoo bottles, for example.

Once again, ethylene glycol is the focus.

It is one of the two monomers of the polyester and, as the researchers report in the journal "Angewandte Chemie", is decisive for the simple decomposition of the polymer - it serves as a sort of predetermined breaking point.

The polyester can be completely broken down into its monomers by adding fungal enzymes.

The work is done by so-called esterases, whose natural task is to decompose esters.

According to the researchers, even industrial composting under standardized standards is conceivable within two months.

Thus, not only is a closed cycle possible, but also rapid degradation is guaranteed if the plastic ends up in the environment.

The researchers now want to investigate whether the polyester also degrades in natural environments.