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How science is enabling sustainable plastics to create a greener world

Plastics are an integral part of the global economy and they have helped build the modern world. Future technologies central to reducing our reliance on fossil fuels will also require plastics. Their unrivalled flexibility, durability, versatility and low cost has ensured their use in almost every single industry. But the development of these amazing polymers has come with unintended consequences.

Recently single-use plastics have plagued the news headlines; they often cannot be recycled and can take hundreds of years to biodegrade. Each minute the equivalent of one rubbish truck of plastic leaks into streams and rivers, ultimately ending up in our oceans. The Ellen MacArthur Foundation Report – The New Plastics Economy predicts there could be more plastic than fish in the world’s oceans by 2050.

The use of disposable packaging has been increasing during the COVID-19 pandemic, as many restaurants, pubs and coffee shops have resorted to takeout meals and more products in supermarkets have plastic wrapping to ensure safety and hygiene which would not usually be there. Lockdown living has increased waste packaging as a result of grocery deliveries, online shopping and takeaways.

As we shift from survival more into recovery, the pandemic could be a unique opportunity to reset our way of life and establish a greener future at the top of the agenda. Battling with our global reliance on plastic and its impact on the environment means taking urgent and radical action at every point of the plastic cycle.

Scientific research is key to understanding and mitigating the environmental impact of the plastics we use today. Advances have been made to develop more efficient ways to recycle plastics and create more sustainable alternatives.

The Centre for Sustainable and Circular Technologies at the University of Bath runs an annual showcase to share the interdisciplinary work of postgraduate students, academics and collaborators. In December 2020, during its first virtual run, the event explored a number of new sustainable technologies and some of them centred around plastics and how to make a greener world.

New recycling technologies

The Ellen MacArthur Foundation cites that out of nearly 78 million tonnes of plastic waste produced every year, 14% is collected for recycling and due to limitations only 2% of that gets recycled into the same quality of plastic. That leaves huge quantities of collected recycling getting buried in landfills, burnt in incineration plants or leaked into our oceans.

Recycling Technologies is developing an innovative circular economy solution for plastic whereby they have created a solution for its end-of-life.

Marvine Besong is Technical Director at Recycling Technologies: “Our process can change the story of plastic by turning waste into a valuable feedstock for new plastic production, bridging the gap between the waste and petrochemical sectors to close the loop in the plastics value chain.

“Our solution integrates with existing waste management and recycling infrastructure, allowing for ease of installation and rapid scalability. The widespread adoption of our technology can help turn off the tap, stopping plastic waste from entering the environment. In doing so we’ll offset CO2 emissions, retain valuable resources within the economy and displace the use of virgin fossil resources whilst enhancing and complementing existing mechanical recycling efforts,” said Marvine Besong.

The innovative chemical recycling process that Recycling Technologies has developed compensates for the limitations currently faced with mechanical recycling, and the company envisages being able to recycle up to 90% of all plastics.

“The RT7000 is a patented technology that can recycle mixed plastic waste like films, packaging and black plastics which cannot be mechanically recycled,” explained Marvine Besong. “Through thermal cracking, it converts the waste into a chemical feedstock called Plaxx®. This feedstock can be used by the petrochemical industry to make more plastic, providing a circular economy solution.

“The benefit of feedstock recycling is that this process can be repeated over and over again, and the beauty of it is that the output material is as good or identical as the virgin material – so there is no loss of quality. The RT7000 is capable of dealing with a wide range of residual plastics and therefore it reduces the requirement for pre-sorting,” added Marvine Besong.

The RT7000 is currently in the procurement and construction phase, to be installed in Binn Ecopark in Scotland, a former landfill site that is now a circular economy recycling centre, in Q4 2021. Their 2018 1/10th scale demonstration plant, termed Beta Plant, based in Swindon, has been supplying Plaxx® to customers for testing and it provided the basis of design for Binn Ecopark’s full-scale installation.

Recycling Technologies is also working in collaboration with an Indonesian recycling company to pilot an advanced Plastics Recycling Facility. The project will address the collection and recycling in Indonesia of more than 90% of all plastic types from households, including hard to recycle sachets, pouches, films and bottles.

The company is not stopped there, Recycling Technologies has also signed a joint agreement with Ineos Styrolution, the largest polystyrene producer in the world, to develop a process to recycle the monomers back into polystyrene – a valuable resource in today’s economy that is currently incinerated or sent to landfill.

Recycling aliphatic polyesters (PLA)

PLA or polylactic acid is a polymer that provides a range of unique bioplastics. PLA is both bio-based (made from natural raw materials) and biodegradable (compostable under industrial composting conditions). In today’s economy, PLA is found in a broad range of established markets such as food packaging and disposable cups, organic waste bags, tea bags, toys and 3D printing filaments. But a lot of the PLA used is being taken to landfill or incinerated.

Global brands such as McDonalds, Nestle and Unilever have made public pledges to increase recycling and some of the targets set are ambitious. New scientific discoveries and technologies have a big role to play in ensuring there are ways to resolve these challenges.

PLA is one of the first renewable polymers able to compete with conventional polymers in terms of performance. It is also three times less carbon-intensive to manufacture.

Dr Gerrit Gobius du Sart is Principal Scientist at Total Corbion PLA and he has extensive expertise in R&D polymer chemistry and sustainable bio-based polymers:

“PLA is certified as industrially compostable by the EN13432 standard which then poses a viable end-of-life solution in those applications where food waste can be diverted from landfill. For other applications, it might be much preferred to preserve the material value of PLA and consider recycling. But can it be done? We think it’s possible to recycle PLA and Total Corbion PLA is planning to launch chemically recycled PLA later this year under the brand name Luminy®. We have our first PLA bioplastics plant in Thailand, with a capacity of 75,000 tonnes per year of PLA, and we’re planning a second plant based in France.”

So how does this highly versatile polymer start and finish its life cycle?

“Lactic acid, obtained through the fermentation of sugar or starch, is the raw material used to produce polylactic acid (PLA). Lactic acid is converted into a monomer, lactide, which is then polymerised to form PLA. At the end of its useful life, PLA can be industrially composted or depolymerised to obtain the initial monomer (lactic acid), which may then be re-utilised to once again produce PLA,” explained Dr Gobius du Sart.

“Recycling polyesters like PLA is also about equilibria – maintaining its starting materials; lactic acid, its oligomers, polylactic acid and lactides and their properties is all possible in industrial production.

“Owing to its aliphatic polyester chemical and physical properties, PLA has numerous end-of-life options and it can be designed to meet consumer needs,” said Dr Gobius du Sart.

The PLA being produced by Total Corbion is recyclable and biodegradable and it is being used for packaging, consumer goods, 3D printing, clothing and automobiles.

Upcycling polyethylene plastic waste

Polyethylene is a polymer that comprises about a third of all plastics produced and one of the most long-lived in the environment. There are ways to recycle waste polyethylene, but so far none are able to upcycle and add value.

But scientists in the US have developed a new method to mitigate the accumulation of plastic waste, recoup its value and reduce our dependency on the oil used to manufacture plastics.

The researchers discovered a catalytic route to transform waste plastic to valuable products via tandem hydrogenolysis/aromatisation. Professor Susannah Scott, University of California – Santa Barbara: “Conventional methods require high temperatures of approximately 5000C to break down polyethylene chains into small pieces. We’ve been able to bring this temperature down to below 3000C and convert polyethylene over a platinum on alumina catalyst, without the need for added hydrogen or solvent.

“The tandem reaction breaks the carbon-carbon bonds and rearranges the polymer to form long-chain alkylaromatic molecules in high yields efficiently – at low cost and with minimal energy loss,” explained Professor Scott.

These high-value alkylaromatic molecules that are generated from the recycled carbon can be adapted for widespread everyday use in solvents, paints, lubricants, detergents, pharmaceuticals and many other uses.

The innovative catalytic process discovered by Professor Scott and her team represents a new direction for the end of life of plastics; it ensures that waste plastics that have so far been very challenging to recycle can become more valuable as raw materials through efficient upcycling instead of languishing in landfills, being incinerated or ending up in our oceans.

Developing biodegradable alternatives to plastic microbeads

Plastic microbeads are plastic particles smaller than 5mm and they are added to cosmetics and personal care products, often as exfoliants, emulsifiers and fillers. Once used they get washed away into our sewers and then into our oceans where they enter the marine food chain.

Microbeads are present in their trillions; they are not biodegradable and are almost impossible to remove. It is estimated between 80,000 and 219,000 tonnes of microplastics are flushed into the sea every year in Europe. Greenpeace refers to the issue as a “toxic time bomb” because microplastics can both release and absorb toxins, which can then move throughout the marine food chain.

Microplastics have been detected in the food and drink that we consume but scientists are yet to form a complete understanding of the health implications posed.

More than 15 countries, including the UK, have taken steps to ban microbeads. However, the issue still persists because the bans only rule out certain uses of microbeads, such as exfoliant in rinse-off cosmetic products but not in leave-on cosmetics, and there are still many countries that continue to allow their use in any application. Furthermore, the focus tends to be on their use in toiletries and cosmetics, when microbeads are also used in detergents, paints, medicine, construction, oil and gas, and agriculture and horticulture.

Natural alternatives for microbeads that are less damaging to the marine ecosystem are being sought, and the University of Bath has developed biodegradable beads made from cellulose.

Naturbeads is a spin-off company that began at the University’s Centre for Sustainable and Circular Technologies: “Cellulose is natural, abundant, eco-friendly, renewable and biodegradable,” explains Dr Giovanna Laudisio, CEO and Co-Founder of Naturbeads.

“Naturbeads can be manufactured competitively at different scales and with properties matching plastic microparticles. In our process, the cellulose is dissolved and then droplets of it are added to a solution, which helps harden them into tiny beads. These microbeads are robust enough to remain stable in a bottle of your favourite shower gel, but they can easily be broken down by organisms at the sewage treatment works or in the environment within a short period of time.”

The team anticipate using cellulose from a range of waste sources including from the paper-making industry as a sustainable source of raw material.

This transformational project began with Innovate UK funding and support from Sky Ocean Ventures to build two pilot plants to make cellulose beads. Their innovation has won numerous awards and they are now in the process of scaling up production to serve their first customers.

Naturbeads is working with industrial partners to test the cellulose beads in multiple applications ranging from personal care and cosmetics to paints and coatings, medical, oil and gas and biocatalysis applications.

Ciaran Callaghan is a postgraduate student at the University of Bath working alongside Naturbeads to improve the commercial viability of biodegradable cellulose microbeads. His work focuses on fine-tuning the size of cellulose microbeads and their size distribution to target new markets by producing cellulose microbeads at previously unreachable size ranges.

“This project involves investigating the use of Rotary Jet Atomization to produce microbeads across a range of sizes using various biopolymers, and to increase the throughput and efficiency of this process. It’s hoped that this new route to producing biodegradable microbeads will be used by my research colleague Hudson Carvalho, to create microbeads capable of effectively delivering micronutrients in agriculture.”

Professor Hudson Carvalho at the University of Sao Paulo:

“Agriculture is under pressure. Productivity needs to double by 2050 in line with global population growth but there is limited space to extend farming. Other challenges faced are around rising prices, oil scarcity and sustainability. Over the past 20 years, productivity of long-term cereal yields in the UK has stagnated due to bottlenecks caused by water availability, genetic traits, pest management and plant nutrition.

“Our research focuses on plant nutrition and how we can increase productivity. We have found that by matching the release and uptake of nutrients we can reduce stress, losses, chemicals in the tank mixture, costs and increase efficiency,” said Professor Carvalho.

The transatlantic team have been working using cellulose microbeads to control the release of zinc to plant crops.

“The team at the University of Bath load the microbeads with zinc and we then conduct X-ray fluorescence experiments here in Brazil to monitor how long it takes to release it and get taken up by the plant,” Professor Carvalho.

“What we found is that we have to fine-tune the beads otherwise the release happens too quickly – in a matter of hours when we need it to happen in weeks. The delivery of zinc needs to match the plant’s requirements.

“We’ve also done some research with coffee beans and the application of a ‘nutrient cocktail’ which increases the cell wall thickness to help prevent a disease called coffee rust and reduce the necessity of pesticides. However, we had to do as many as six applications per year of the cocktail to get it right and due to the costs involved in that process, it’s not commercially viable. We hope that loading this ‘nutrient cocktail’ within the fine-tuned beads will make this strategy for controlling coffee rust disease feasible.

“Once again we need to fine-tune the release rate to match the plant’s necessity, make the beads ‘stick’ to the leaf surface and the beads small enough to avoid blocking the spray nozzles. We also need to ensure that the system is cost-effective,” explained Professor Carvalho.

These examples of ongoing research show that cellulose is a workable biodegradable alternative to plastic microbeads that can mimic the performance of plastics and ensure that its use does not leave harmful residues in our environment for longer than nature intended.

Summary

There are many exciting projects in development that change the face of plastics for a more sustainable future. But more technical solutions are urgently needed to ensure that future plastics can retain their useful properties but have a reduced impact on the environment. Efforts to develop efficient ways to recycle and reuse today’s plastics and create alternatives that are fully sustainable and eco-friendly are imperative. While doing so, we also need to reduce and even reverse the damage that plastic pollution has already caused.

Our global dependency on plastics is set to rise and, without scientific advances and their commercial application, this could have huge environmental implications. According to a report published by the World Economic Forum, by 2050 plastics manufacturing and processing may account for as much as 20% of petroleum consumer globally and 15% of the annual carbon emissions budget.

The time is now to invest in new technologies to reduce the impact of today’s plastics, create a circular economy and build a new future for plastics.

Read more about the CSCT’s upcoming annual showcase ‘Race to Zero’ in July 2021.

By 22 March 2021 0 Comments
 

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