Shoes decompose in sea water enough for sea creatures to eat.

And it can help fight plastic pollution.

Leather can take up to 40 years to biodegrade, while rubber soles can take up to 80 years.

Around 600 million shoes are thrown away each year in the UK alone.

Scientists at the University of California, San Diego have created a plimsoll that begins to decompose after just four weeks underwater. Its materials are designed to be broken down by sea creatures into their original chemicals, which they can then consume as food.

The researchers say that replacing plastic could solve the problem of pollution that currently plagues the oceans.

Professor Stephen Mayfield said: “Incorrect disposal of plastic has become a huge environmental problem. We have shown that it is absolutely possible to produce high-performance plastic products that can biodegrade in the ocean and be safe. Plastics should not end up in the ocean, but if they do, this material will become food for microorganisms, rather than plastic debris and microplastics that harm aquatic life.”

In 2010, researchers estimated that 8 billion kilograms of plastic ends up in the ocean every year, and a sharp increase is predicted by 2025.

Footwear is a significant contributor to this waste both in water and in landfills, and plastic-based flip flops are the world’s most popular footwear.

When plastic waste enters the ocean, it destroys marine ecosystems and migrates together to form giant garbage piles similar to the 1.6 million square kilometer Great Pacific Garbage Patch.

The material never completely decomposes in the sea, but instead breaks down into tiny microplastics that remain there for centuries.

For the past eight years, Professor Mayfield’s team has been developing polyurethane foams made from algae oil, which they proved in 2020 to degrade rapidly in both water and soil.

The foam also meets commercial requirements for the base of the foot of flip-flops, as well as the shock-absorbing part of the sole of the shoe.

For their new study, published in the journal Science of The Total Environment, the scientists wanted to see if submerging the material in seawater would yield results.

They exposed the specimens to the natural coastal ecosystem at the Ellen Browning Scripps Memorial Pier and Experimental Aquarium for 30 weeks.

Changes in the molecular bonds of the samples were monitored using Fourier transform infrared spectroscopy and visualized using scanning electron microscopy.

It was found that the polyurethane began to degrade after only four weeks, aided by a variety of marine organisms.

“I was surprised to see how many organisms are colonizing this foam in the ocean. It has become something of a microbial reef,” Professor Mayfield added.

Bacteria and fungi broke down the long polyurethane molecules into their original chemicals, which they could then consume as nutrients themselves.

The team then identified these microorganisms and found them in six locations throughout San Diego.

This suggests that the type of creature capable of decomposing the material is common throughout the natural marine environment.

“No single discipline can solve these universal environmental problems, but we have developed a comprehensive solution that works on land – and now we know that biodegradation occurs in the ocean, too,” Professor Mayfield said.

Christina DENISYUK.

Source www.dailymail.co.uk

Photo: Daniel Zhen, Algenesis Inc.