Leather can take 40 years to decompose, and a rubber sole takes up to 80 years. Meanwhile, every single piece of plastic you wear is still on the planet.
This means that 600 million shoes discarded every year in the UK may still be around for thousands of years – but your next pair may not take long.
That’s because scientists from the University of California San Diego have created a Plimsoll platform that begins to biodegrade after just four weeks underwater.
Its substances are designed to be broken down into native chemicals by marine organisms, which can then consume them as nutrients.
Researchers say that replacing plastic could address the pollution currently plaguing the world’s oceans.
Professor Stephen Mayfield said: ‘Improper disposal of plastic in the ocean turns into microplastic particles and has become a massive environmental problem.
We have shown that it is entirely possible to make high-performance plastic products that can also degrade in the oceans.
Scientists from the University of California, San Diego, have created a Plimsoll platform that begins to biodegrade after just four weeks underwater.
Its materials are designed to be broken down into native chemicals by marine organisms, which they can then consume as nutrients
What is biodegradable polyurethane made of?
About half of polyurethane foam is made from oils extracted from algae.
The other half is made of isocyanate which comes from petroleum.
Isocyanates are still biodegradable and edible for microorganisms.
“Some organisms can survive on foam and only some salts, so our foam is actually food for microorganisms,” Professor Mayfield said.
Cube of polyurethane foam made with algae oil
Professor Mayfield added: “The plastic shouldn’t go into the ocean in the first place, but if it does, that substance becomes food for microorganisms and not plastic litter and microplastics that are harmful to aquatic life.”
In 2010, researchers estimated that 8 billion kilograms of plastic ends up in the ocean each year, and a sharp rise is expected by 2025.
Shoes contribute significantly to this waste in both water and landfill, and slippers made of plastic are also the most popular footwear in the world.
When plastic waste enters the ocean, it disrupts marine ecosystems and together they migrate to form giant piles of trash, like the 1.6 million square kilometer Pacific Great Garbage Patch.
This material does not completely decompose in the sea, instead it breaks down into microplastic particles that have remained there for centuries.
Over the past eight years, Professor Mayfield’s team has been developing polyurethane foams made from algae oil, which in 2020 they demonstrated will degrade quickly in compost and soil.
The foam also meets the commercial requirements of the footbed for slippers as well as the shoe cushioning department.
In their new study, published yesterday in Science of The Total Environment, they wanted to test whether submerging the material in seawater would produce the same results.
They exposed the foam samples to a natural near-shore ecosystem at the Ellen Browning Scripps Memorial Pier and Experimental Aquarium over a period of up to 30 weeks.
Changes in the molecular bonding of the samples were tracked using Fourier transform infrared spectroscopy and visualized using electron microscopy.
Shoes contribute significantly to plastic waste in both water and landfill, and slippers made of plastic are also the most popular footwear in the world (stock image)
The team exposed samples of polyurethane foam to a natural near-shore ecosystem at the Ellen Browning Scripps Memorial Pier and Experimental Aquarium over a period of up to 30 weeks. Changes in the molecular bonding of the samples were tracked using Fourier transform infrared spectroscopy and visualized using electron microscopy.
Researchers studied polyurethane foam submerged in the pier of the Scripps Institution of Oceanography
He found that polyurethane began to biodegrade after just four weeks, which was helped by a variety of marine organisms.
Professor Mayfield said: ‘I was surprised to see how many organisms colonize on these foams in the ocean. It becomes something like microbial coral.
Bacteria and fungi have broken down the long polyurethane molecules into original starting chemicals, which can in turn consume them as nutrients.
The team then identified these microorganisms, locating them at six sites throughout San Diego.
This indicates that the type of creatures capable of breaking down matter is widespread throughout the natural marine environment.
“There is no single system that can address these global environmental problems, but we have developed an integrated solution that works on land – and now we also know biodegradation in the ocean,” said Professor Mayfield.
Two panels on the left: photographs of foam samples attached to a Scripps dock at week 0 and week 4. Six panels on the right: scanning electron microscopy images of polyurethane foam (top) and control EVA foam (bottom). A, F: Foam before exposure to sea water; D, G: after 4 weeks under water; e,h: after 12 weeks underwater
Scanning electron microscopy images of polyurethane foam (top) and control ethylene vinyl acetate (EVA) foam (bottom). a, d: foam before exposure to sea water; D, G: after 15 weeks underwater; E, H: After 30 weeks underwater
Eight million tons of plastic find its way into the ocean every year
Of the 30 billion plastic bottles used by households in the UK each year, only 57 per cent are currently recycled.
With half of these bottles going to landfills, half of the plastic bottles that are recycled go to waste.
About 700,000 plastic bottles a day end up as waste.
This is largely due to plastic wrapping around non-recyclable bottles.
Bottles are a major contributor to the increasing amount of plastic waste in the world’s oceans.
Researchers have warned that eight million tons of plastic currently find its way into the ocean each year – the equivalent of one truckload every minute.
A 2016 report revealed that the amount of plastic waste in the world’s oceans will outnumber fish by 2050 unless the world takes drastic measures to recycle it.
At current rates, this will worsen to four trucks per minute in 2050 and outpace local life to become the largest mass inhabiting the oceans.
The Ellen MacArthur Foundation report said 95 per cent of plastic packaging – worth £65 billion – is lost to the economy after a single use.
Available research estimates that there are more than 150 million tons of plastic in the ocean today.
Plastic pollution is destroying the world’s ecosystems, both marine and terrestrial. It fills beaches, hampers animals and chokes entire groups of animals
Scientists have warned that so much plastic is dumped into the sea each year that it would fill five portable bags for every foot of coast on the planet.
More than half of the plastic waste that flows into the oceans comes from just five countries: China, Indonesia, the Philippines, Vietnam and Sri Lanka.
The only industrialized western country in the list of the top 20 plastic polluters is the United States at number 20.
Researchers said that the United States and Europe do not mismanage their collected waste, so plastic waste coming from those countries is due to garbage.
While China is responsible for the 2.4 million tons of plastic that makes its way into the ocean, nearly 28 percent of the global total, the United States contributes only 77,000 tons, less than one percent, according to the study published in the journal Science. Sciences. .