Covering all bases

Research is being conducted into the possibility of recycling and reusing PPE, and even converting hazardous medical waste into hydrogen fuel, as Chris Elliott finds out

Alongside the many tragic deaths, the Covid-19 pandemic has racked up eye-watering costs for the taxpayer in terms of buying personal protective equipment (PPE). Over four and a half months last year, the Department of Health and Social Care reportedly spent £12.5bn securing 32 billion must-haves in the war against the virus: masks, respirators, gloves, aprons, gowns and hand-hygiene products.

Up to the middle of January this year, 7.3 billion of those items had been distributed to health and social care providers. Once they have been used, they are deemed to be infectious waste, which has to be disposed of by landfilling or incineration.

So, what is being done to find ways of recycling PPE? Several projects are under way in the UK that give hope that, in the future, this can be achieved – perhaps even on a large scale.

A baby bottle steriliser, used by the Cardiff team to decontaminate masks in an industrial microwave

At Cardiff University, researchers from the schools of Pharmacy and Pharmaceutical Sciences and Engineering have teamed up to tackle the problem. They have found that certain types of respirators can be disinfected by putting them in an industrial-grade microwave oven for a short time, while masks can be made safe for reuse by subjecting them to dry heat.

Dr Michael Pascoe, research associate at Cardiff, says: ‘In our study, respirators were reprocessed using moist heat in the form of microwave-generated steam. We placed the respirators into a baby bottle steriliser, which also contained a small volume of water. We microwaved the steriliser for 90 seconds, which rapidly killed the simulated contaminant.

‘Respirators could be reprocessed at least three times this way without negatively impacting their ability to filter out virus-sized aerosols.’

Pascoe admits it’s currently a ‘small scale’ solution, but he believes it could be useful for services such as care homes and dental practices, rather than hospitals.

With masks, the team found that exposure to moist heat seriously damaged them, relaxing the fibres in the filtering layer and allowing bacteria to pass through easily. But using dry heat at 80°C for 90 minutes achieved a ‘satisfactory’ level of decontamination, Pascoe says.

‘Dry heat can easily be scaled up for reprocessing en masse. After hearing about our research, a South Wales-based business even reached out and kindly offered us the use of their industrial kiln for mask treatment, if the need arises.’

With masks, the team found that exposure to moist heat seriously damaged them, relaxing the fibres in the filtering layer and allowing bacteria to pass through easily.

At Southampton University, researchers are turning the spotlight on the reuse of masks. They are pioneering a ‘dry decontamination’ method, which uses printed electronics to create a material called non-thermal plasma, which, they say, can deactivate 99.9 per cent of viruses very rapidly. The aim is to produce a ‘decontaminating pouch’ into which used masks can be sealed for treatment.

The research group’s Dr Min Kwan Kim describes the work so far as ‘promising’, adding: ‘It decontaminates masks without using biocidal chemicals, which means the structural and functional integrity of the masks can be maintained.’

Mark Hall, spokesperson for Divert, which works to prevent waste going to landfill, welcomes the ideas: ‘While responding to a sudden, urgent shift in the need for items such as PPE, it’s easy to let our broader goals slip beyond the horizon, but innovations such as this help us create robust, environmentally friendly ways of meeting demand without making environmental sacrifices.’

Another project under way in Wales – by scientists at Swansea University, supported by the Welsh government – is looking into how sunlight can be harnessed to convert hazardous medical waste into hydrogen fuel.

An agar plate (the jelly used to cultivate microbes in the lab at Cardiff University) reveals the bacteria from a section of used face mask. After treatment, plates were free of bacterial growth, indicating they were sanitary

Senior chemistry lecturer Dr Moritz Kuehnel, who is leading the effort, says: ‘It’s called photoreforming, and it utilises catalysts that are able to convert solar energy into chemical energy, much like plants do during photosynthesis. Irradiation with light generates positive and negative charges on the catalyst surface, which are able, respectively, to break down waste and evolve hydrogen.

‘The waste is simply added to a glass tube containing water and small amounts of catalyst powder, and hydrogen bubbles form while the waste is degraded. The positive charges are also able to generate reactive oxygen species, which are known to deactivate various sorts of pathogens, such as bacteria, viruses and fungi. That way, we can simultaneously disinfect and degrade waste – and produce clean hydrogen.’

Conventional recycling requires waste to be cleaned and separated into individual types of plastic, but hospital waste is contaminated and often consists of a range of materials – for example, a surgical face mask is made from polypropylene, but the ear loops are made from spandex, making it hard to recycle, Kuehnel says. Incineration is then seen as the cheapest option – but photoreforming can tackle contaminated and mixed waste alike.

The work is still at the experimental stage, and a commercial process is a few years down the line, yet, Kuehnel says. But because, in principle, only simple materials are needed, it may prove useful, especially in countries without widespread recycling and waste management infrastructure.

Plastic in a tube undergoing photoreforming at Swansea

If PPE can’t be made fit for reuse, why not turn it into something else? Wilko’s in-store face mask recycling scheme, for example, is shredding collected masks into raw materials, which can be sustainably refashioned into products ranging from other safety materials for businesses, to building materials and even quality, durable public space furniture.

Similarly, Cornwall social enterprise Waterhaul is working with the Royal Cornwall Hospital, in Truro, to recycle nearly a tonne of used surgical masks and PPE every month – melting them into plastic blocks that can be made into bins and building materials.

The hospital trust gets through around 10,000 masks a day at its three sites, and has now joined forces with recycling machinery manufacturer Thermal Compaction Group to produce the blocks.

Roz Davies, the hospital’s general manager, says: ‘We hope this will be a real game-changer in the way we tackle single-use PPE.’

This feature first appeared in the May/June issue of Circular magazine. 

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