PPE for the planet

Personal protective equipment (PPE) is vital. For those working among the public throughout the Covid-19 pandemic, it has been the only thing between them and a potentially deadly virus – when it’s been available, that is. The world hopes it’s through the worst of the shortages now, but as single-use gloves and masks begin to wash up on beaches, the demand for alternatives that protect both people and the planet they live on grows more urgent.

That said, the vast majority of PPE waste still stems from clinical settings where it is graded as potentially infectious, sterilised and then incinerated or sent to a landfill. Incinerated plastic products won’t get washed up on a beach in the same way, but incineration releases the carbon locked in the plastic back into the atmosphere as CO2. What’s more, those products are then replaced, which generates roughly 3t of CO2 per tonne of plastic. The bloating of plastic waste during the pandemic is particularly hard to swallow given the hard-won headway that had been made by 2020, both in government policymaking worldwide and consumer behaviour. “Pollution and climate change are an extinction-level event much bigger than a virus,” says Michael Shaver at the Sustainable Materials Innovation Hub at the University of Manchester in the UK. Thankfully, researchers and companies around the world have been working on more sustainable approaches to both the creation and disposal of PPE, tackling not just these products’ short-working lives, but also the harm they cause once they’re done.

Long-life PPE

Extending the lifetime of PPE to reduce the environmental cost per use has been an attractive option, partly because it also alleviates the strain on meeting a ballooning demand for supplies. The UK government alone requested 84t of medical equipment, including 400,000 gowns, in a single order to meet gross shortfalls as their Covid-19 cases began to peak in April 2020. Efforts to prolong product lifetimes are often combined with the development of technologies that will also improve performance, thereby adding further value. One example is the face mask recently released by planarTECH and IDEATI.

Both companies work with graphene, a crystalline carbon material just one atom thick. Its extraordinary properties have earned it the tag ‘wonder material’, as well as unprecedented research and development investments, and perhaps a rather premature reputation for overpromising and under-delivering in the commercial sector. Back in January 2020, when coronavirus was just starting to escape China, IDEATI was developing a mask to block pollution, which is a big problem in the company’s home city of Bangkok. Face masks were already popular in much of Asia to guard against pollution and pollen – as well as the transmission of germs – and J Patrick Frantz, CEO of planarTECH (a former supplier to IDEATI), suggested testing the masks for graphene’s reported antibacterial and antimicrobial properties. When they found that the mask killed all the bacteria on it, they teamed up, changed focus and pushed into the PPE sector.

The face masks use graphene mixed into a resin and screen-printed onto a polyester fabric, which is stitched onto cotton. Graphene’s fine-filtering properties, which were the initial prompt for its use in masks, mean it has a comparable performance with a surgical mask in blocking the transmission of particles – more than 80% for particles in the 100nm size range of the SARS CoV-2 coronavirus. However, graphene’s impressive conductivity also gives the mask electrostatic properties that can rupture a bacterium’s protein shell. Tests are under way to confirm a similar effect on viruses, although these are more complicated. A virus needs to infect a cell to reproduce, so it becomes hard to tell whether the mask is killing the virus or the host cell.

Either way, wearers have also suggested that the high-thermal conductivity makes the mask more comfortable to wear. Most importantly, from a sustainability point of view, it can be washed over 50 times without degrading the performance. Consumer response has been positive and the companies are now looking at expanding their range in PPE to other products. “It’s one of the applications that I’ve seen that can be massproduced and I can confidently say the graphene is doing something in the product,” says Frantz.

While the small fractions of graphene that tend to be used in products mitigates the financial and environmental cost of its production, another approach is to improve the antiviral properties of the plastic fibres already used for PPE, such as polypropylene. In the Laboratory for Advanced Materials at Pittsburgh University, US, led by Paul Leu, Anthony Galante has coated polypropylene microfibres, similar in width to human hair, with polytetrafluoroethylene nanoparticles a thousand times smaller. The overhang of the nanoparticle on the microfibre traps air, which forms a barrier that helps the surface repel bodily fluids like blood.

As a result, these fluids – and any viruses in them – roll off the textiles made from the nanoparticle-coated fibres, like water off a lotus leaf. What’s more, they are robustly reusable. Galante was able to scratch the surface with a razor and subject the textile to 12 ultrasonic washes without degrading its performance.

End of life

Inevitably, even a reusable face mask will need replacing. The question of what happens then still needs to be solved. Otherwise, it’s just the same story on a different timeline. A growing number of biodegradable and compostable plastic products are emerging, and there are now teams looking into their applicability in PPE. While these shouldn’t choke up waterways, they still end up releasing the CO2 that was locked up in the plastic into the atmosphere. Biodegradable and compostable plastic tends to be plant-based, so, in a sense, that CO2 would have been released anyway as the source plant died and decomposed. However, they also need replacing, and that goes for all the PPE and other plastic in clinical waste destined for incineration.

Tradebe Healthcare handles clinical waste streams from many NHS Trusts across the UK, including all of NHS Scotland’s ‘orange bag’ operating theatre waste – from masks, gloves and aprons to cotton buds, dosing equipment, sharps and medicine containers. That added up to tens of thousands of tonnes per year even before coronavirus hit, and all of it undergoes sterilising heat treatment before final disposal. Tradebe contacted Impact Recycling to see if there might be a way of recovering some of the plastic from this waste.

Picking plastic

Since Tradebe has to sterilise the waste before it can go anywhere anyway, infection levels were not the issue. Identifying the plastics isn’t a problem, either – the optical sorters commonly used for domestic waste can do this. The issue is the mechanics of the processes that actually separate the plastics, which typically air blow scraps of waste from a processing line to redirect it to different disposal or recycling routes.

All the available options for the sterilisation process ultimately use hot steam to kill pathogens, so the waste is not just jumbled but tightly stuck together with steam. “Picking through the material, I realised why existing technology that uses air or electrostatics doesn’t work,” says James Finlayson, chief technology officer at Impact Recycling. “It’s really well mixed.”

Impact turned to its baffled oscillation separation system (BOSS), a technology originally developed to separate polypropylene and polyethylene – two common plastics that are fiendishly difficult to separate because their properties are almost identical. BOSS technology sorts these plastics by using a large column flushed through with water. Oscillating up and down the column, sieve-like ‘baffles’ are used to form eddies in the water. Although very similar, polypropylene is slightly less dense than polyethylene – 0.93g/cm3 compared with 0.92g/cm3 – and it is more crystalline, which means it ends up in more angular fragments after the crushing and grinding in the first stage of recycling. These slight differences add up, making the polypropylene far more likely to get caught up in an eddy in the BOSS column while the polyethylene is flushed through.

The unintended impact of these eddies is that they also separate the clingy clumps of sharps, rigids and films in clinical waste. Like someone clinging to a dinghy in a storm, under the constant buffeting by torrents of eddies in the BOSS cylinder, the different components of the clumps inevitably come apart. They can then pass through the same recycling routes like any other waste.

The team found that 70% of the orange bag waste Tradebe sent them was plastic, of which 30% is rigid plastic – medicine bottles, for example – and the remaining 40% are films. The company already has the technology to separate and recover the rigids, and expects that by Christmas it will be able to recover the single-plastic films – which are more easily recycled – from thermally joined multilayer films. For this, the BOSS 2D technology for films is currently being upscaled from a working laboratory prototype. “Our footprint of carbon is 0.1t per tonne,” says Impact Recycling CEO David Walsh – 96% less than producing virgin plastic, according to extensive life cycle comparative analyses.

To innovators who like a challenge, the ability to produce PPE that can be reused, composted or recycled was perhaps never in question. That efforts to tackle PPE waste are spread across the board is also encouraging, since studies suggest that no one approach alone can tame the upwards trend in plastic pollution. But whether these alternatives are actually reused and recycled is always harder to gauge, and that’s why the investment and success the sector is starting to accrue is a real cause for optimism.

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