Commercially degradable commercial quality flip-flops. Credit: Stephen Mayfield, UC San Diego.
As the most popular shoes in the world, flip-flops are responsible for a cumbersome percentage of plastic waste that ends up in landfills, on seawalls and in our oceans. Scientists at the University of California San Diego have spent years solving this problem, and now they have taken a step further toward pursuing this mission.
Instead of their chemistry, the team of researchers formulated polyurethane foams, made from algae oil, to meet commercial specifications for midsole shoes and the footbed of flip-flops. The results of their study are published in Bioresource technology report and describe the team’s successful development of these sustainable, consumer-ready and biodegradable materials.
The research was a collaboration between UC San Diego and startup Algenesis Materials – a materials science and technology company. The project was led together by graduate Natasha Gunawan from the labs of professors Michael Burkart (Department of Physical Sciences) and Stephen Mayfield (Department of Biological Sciences), and by Marissa Tessman from Algenesis. It is the latest in a series of recent research studies that, according to Burkart, collectively offer a complete solution to the plastic problem – at least for polyurethanes.
“The paper shows that we have commercial grade foams that degrade biologically in the natural environment,” Mayfield said. “After hundreds of formulations, we have finally reached one that meets commercial specifications. These foams are 52 percent biocontinent – eventually we will reach 100 percent.”
Biodegradation of PU cubes over 12 weeks. Degradation was analyzed by A) Change in appearance, B) Cube mass and C) Maximum force at 50% compression force deflection (CFD). Error bars indicate sample deviations from the triangle measurements. For compost and soil mass loss, p <0.01 and for compost and soil CFD, p <0.01 (Table 2 in published paper). Credit: Stephen Mayfield, UC San Diego
In addition to devising the exact formulation for commercial quality foams, the researchers worked with Algenesis to not only make the shoes, but also degrade them. Mayfield noted that scientists have shown that commercial products such as polyesters, bioplastics (PLA) and fossil fuels (PET) can degrade biologically, but only in the context of lab tests or industrial composting.
“We have redesigned polyurethanes with bio-based monomers to meet the high material specifications for shoes while keeping the chemistry appropriate, in theory, so that the shoes could degrade biologically,” Mayfield explained.
Adjusting their custom foams by immersing them in traditional compost and soil, the team discovered that the materials degrade after just 16 weeks. During the degradation period, to account for all the toxicity, scientists, led by UC San Diego’s Skip Pomeroy, measured each molecule from the biodegradable materials. They also identified the organisms that degrade the foams.
“We took the enzymes of the organisms that degraded the foams and showed that we could use them to depolymerize these polyurethane products, and then identified the intermediate steps that take place in the process,” Mayfield said, adding, ” We then showed that we could isolate the depolymerized products and use them to synthesize new polyurethane monomers, completing a ‘bio loop’. “
Footbed of flip-flops is pulled from a mold. Credit: Stephen Mayfield, UC San Diego.
This complete recyclability of commercial products is the next step in the scientist’s ongoing mission to address the current problems of production and waste management we have with plastics – which, if not addressed, will result in 96 billion tonnes plastic in landfills or the natural environment until 2050 According to Pomeroy, this environmentally unfriendly practice began about 60 years ago with the development of plastic.
“If you could turn back the clock and re-imagine how you could make the petroleum polymer industry, would you do the same thing today as we did today? There’s a bunch of plastic floating in every ocean on this planet. which suggests we should not have done it that way, “Pomeroy stated.
While commercially on track for production, doing so economically is a matter of scale that scientists are collaborating with their production partners.
“People are getting around on plastic ocean pollution and starting to ask for products that can address what has become an environmental disaster,” said Tom Cooke, president of Algenesis. “We’re in the right place at the right time.”
IMS of compost-derived organisms grows on PUM9 film agar plates. A) Photo of culture growth one week after incubation, with scale bar for all images. B – F) Mass distributions indicating the location and relative intensity of the given m / z value and its molecular association. G) Battle for relative intensity for B – F. See additional data for evidence of molecular commands. Credit: Stephen Mayfield, UC San Diego.
The team’s efforts are also reflected in the establishment of the Center for Renewable Materials at UC San Diego. Started by Burkart, Mayfield, Pomeroy and their co-founders Brian Palenik (Scripps Institution of Oceanography) and Larissa Podust (Skaggs School of Pharmacy and Pharmaceutical Sciences), the center focuses on three key goals: the development of sustainable and sustainable monomers made of algae and other biological sources; their formulation in polymers for various applications, the creation of synthetic biology platforms for the production of monomers and crosslinking components; and the development and understanding of biological degradation of sustainable polymers.
“The life of material must be proportional to the life of the product,” Mayfield said. “We don’t need material that lasts 500 years on a product that you will only use for a year or two.”
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Natasha R. Gunawan et al., Rapid biological degradation of durable polyurethane foams with identification of associated microorganisms and distribution products, Bioresource technology report (2020). DOI: 10.1016 / j.biteb.2020.100513
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Citation: New science behind biologically degradable algae-based flip-flops (2020 7 August) retrieved 8 August 2020 from https://phys.org/news/2020-08-science-biodegradable-algae-based-flip-flops.html
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