There is one artificial material that you can see in the soil, the air, and in the deepest ocean trenches. It is so permanent that the majority of what has been produced still exists in our ecosystem. Having made its access into the food chain, it penetrates our bodies, running in our blood into our organs, still finding its entrance into the human placenta.
It is, of course, plastic, and this endurance is also what executes the material so valuable. Cables are growing across ocean floors, water pipes beneath the ground, and packaging that holds food fresh all rely on this quality.
Efficiently converting plastic by traditional means is particularly tricky, and only 9% of all plastic ever made has been recycled into new plastics. But what if there was a method to turn plastic back into the material it was made from? The “next grand challenge” for polymer chemistry – the field effective for creating plastics – is discovering to undo the method by converting plastics back into oil.
Infinite Recycling – Chemical Recycling
Alternatively, of a method where some plastics are discarded because of the wrong color or formed of co-plastic, chemical recycling could inspect all types of plastic supported into an “infinite” recycling system.
This method – known as chemical recycling – has been examined as a viable option to conventional recycling for decades. This, coupled with the expansive oil price, sometimes makes it more affordable to produce new plastic products than to recycle existing plastic.
Every year, more than 380 million tonnes of plastic are produced worldwide. That’s about the same as 2,700,000 blue whales – more than 100 times the weight of the entire blue whale population. Just 16% of plastic waste is recycled to make new plastics, while 40% is sent to landfills, 25% to incineration, and 19% is dumped.
Many plastics that could be converted – such as polyethylene terephthalate – PET, used for containers and other packaging – finishes up in a landfill. This is usually due to uncertainty about curbside recycling or contamination with food or different types of waste.
Other plastics – such as vegetable bags and other food containers – get their way to landfills because they are produced up of a blend of different plastics that can’t be split apart in a recycling plant. Litter dropped in the road and lightweight substitutes left in landfill sites or illegally dumped can be carried by the wind or washed into rivers by the rain, ending up in the ocean.
Chemical recycling is an attempt to convert the unrecyclable. Moderately of a system where unusual plastics are discarded because of the wrong color or made of co-ex, chemical recycling could understand all kinds of plastic fed into an “infinite” recycling system that unmakes plastics back into oil, so they can then be used to make plastic again.
The custom plastic that is now recycled is more extra of a downwards spiral than an infinite loop. Plastics are typically converted mechanically: they are sorted, cleaned, shredded, blended, and remolded. Each time plastic is recovered this way, its quality deteriorates. When the plastic is melted, the polymer chains are partially broken down, reducing its tensile strength and viscosity, making it more difficult to process.
The original, lower-grade plastic often becomes inadequate for use in food packaging. Most plastic can be recycled a minimal number of times before it is so degraded it converts unusable.
The emerging application of chemical recycling strives to sidestep this problem by breaking plastic down into its chemical building slabs, which can then be applied for fuels or reincarnate new plastics.
In the UK, Mura Technology has begun construction of the world’s first commercial-scale plant to recycle all kinds of plastic.
The various versatile variant of chemical recycling is “feedstock recycling.” Also known as thermal conversion, feedstock recycling is any method that breaks polymers down into simpler molecules using heat.
The method is pretty straightforward – take a plastic drinks bottle. You set it out with your recycling for collecting. It is received, along with all the other waste, to a sorting ability. The waste is sorted, either automatically or by hand, into various materials and different plastics.
The bottle is washed, stripped, and collected into a bale ready for transport to the recycling center – so far, the same as the standard process. Then comes the chemical recycling: the plastic that formerly made up your bottle could be taken to a pyrolysis center where it is melted down. Next, it is fed into the pyrolysis reactor, where it is heated to extreme temperatures. This process turns the plastic into a gas that is then cooled to condense into an oil-like liquid and finally distilled into fractions that can be used for different purposes.
Chemical recycling systems are being trialed over the world. UK-based Recycling Technologies has generated a pyrolysis machine that transforms hard-to-recycle plastic such as films, bags, and multi-layered plastics into Plaxx. This fluid hydrocarbon feedstock can be used to create new virgin quality plastic. The first commercial-scale unit was installed in Perth in Scotland in 2020.
Plastic energy has two commercial-scale pyrolysis plants in Spain and proposes to expand into France, the Netherlands, and the UK. These factories convert hard-to-recycle plastic waste, such as bakery wrappers, dry pet food pouches, and breakfast cereal bags, into items called “tacoil.” This feedstock can be used to make food-grade plastics.
In the US, the chemical company Ineos has become the first to use a depolymerization technique on a commercial scale to produce recycled polyethylene, which goes into carrier bags and shrink film. Ineos also has plans to build several new pyrolysis recycling plants.
In the UK, Mura Technology has begun construction of the world’s first commercial-scale plant to recycle all kinds of plastic. The plant can handle mixed plastic, colored plastic, the plastic of all composites, all stages of decay, even plastic contaminated with food or other kinds of waste.
Mura’s “hydrothermal” technique is a type of feedstock recycling using water inside the reactor chamber to spread heat evenly throughout. Heated to extreme temperatures but pressurized to prevent evaporation, water becomes “supercritical” – not a solid, liquid, nor gas. This use of supercritical water, avoiding the need to heat the chambers from the outside that Mura says, makes the technique inherently scalable.
“If you heat the reactor from the outside, keeping an even temperature distribution is hard. The bigger you go, the harder it gets. It’s a bit like cooking,” explained Mura’s chief executive, Steve Mahon. “It’s hard to fry a big steak all the way through, but if you boil it, it’s easy to make sure it’s cooked all the way evenly through.”
The plastic waste arrives on-site in bales – contaminated, multi-layer plastic such as flexible films and rigid trays that would otherwise have gone to incineration or energy-from-waste plants. The bales are fed into the front-end sorting facility to remove any inorganic contaminants such as glass, metal, or grit. Organic contaminants such as food residue or soil can pass through the process. The plastic is then shredded and cleaned before being mixed with supercritical water.
Once this high-pressure system is depressurized and the waste exits the reactors, most liquid flashes off as vapor. This vapor is cooled in a distillation column. The condensed liquids are separated on a boiling range to produce four hydrocarbon liquids and oils: naphtha, distillate gas oil, heavy gas oil, and heavy wax residue, akin to bitumen. These products are then shipped to the petrochemical industry.
There is no down-cycling as with other feedstock techniques, as the polymer bonds can be formed anew, meaning the plastics can be infinitely recycled. With a conversion rate of more than 99%, nearly all plastic turns into a functional product.
Mahon said: “The hydrocarbon element of the feedstock will be converted into new, stable hydrocarbon products for use in the manufacture of new plastics and other chemicals.” Even the “fillers” used in some plastics – such as chalk, colorants, and plasticizers – aren’t a problem. “These drop into our heaviest hydrocarbon product, heavy wax residue, which is a bitumen-type binder for use in the construction industry.”
The hot, excess gases generated during the process will heat the water, increasing its energy efficiency, and the plant will be powered by 40% renewable energy. “We want to use as much renewable energy as possible and will be seeking, wherever practical, to aim for 100%,” says Mahon.
Mura’s Teesside plant, due for completion in 2022, aims to process 80,000 tonnes of previously unrecyclable plastic waste every year, as a blueprint for a global rollout, with sites planned in Germany and the US. By 2025, the company plans to provide one million tonnes of recycling capacity in operation or development globally.
“[Our] recycling of waste plastic into virgin-equivalent feedstocks provides the ingredients to create 100% recycled plastics with no limit to the number of times the same material can be recycled – decoupling plastic production from fossil resource and entering plastic into a circular economy,” says Mahon.
Scientists such as Sharon George, senior lecturer in environmental science at Keele University, have welcomed Mura’s development. “This overcomes the quality challenge by ‘unmaking’ the plastic polymer to give us the raw chemical building blocks to start again,” says George. “This is true circular recycling.”
Yet, in the past 30 years, chemical recycling has shown severe limits. It is energy-intensive, has faced technical challenges, and proved difficult to scale up to industrial levels.
In 2020, a report by the Global Alliance for Incinerator Alternatives (Gaia), a group of organizations and individuals who promote social movements to reduce waste and pollution, concluded that chemical recycling is polluting, Energy-intensive, and prone to technical failures. The report concluded that chemical recycling was not a viable solution to the plastic problem, especially at the pace and scale needed.
Additionally, suppose the end product of chemical recycling is an oil used for fuel. In that case, the process does not reduce the need for virgin plastic, and burning such fuels would release greenhouse gases just as ordinary fossil fuels do.
“Environmental NGOs are keeping a close eye on emerging recycling methods,” says Paula Chin, sustainable materials specialist at the conservation organization WWF. “These technologies are in their infancy, and they are by no means the silver bullet solution to the plastic waste problem. We should focus on increasing resource efficiency as a way to minimize waste through greater reuse, refill and repair systems – not relying on recycling to be the savior.”
But Mura argues that their plant will fill a much-needed niche. “[Chemical] recycling is a new sector, but the scale at which it is developing, specifically for Mura, shows both the urgent need for new technology to tackle the rising problem of plastic waste and environmental leakage and an opportunity to recycle a valuable ready-resource, which is currently going to waste,” Mahon says.
Mura’s process aims to complement existing mechanical processes and infrastructure, not compete with them, recycling materials that would otherwise go to landfills, incineration or into the environment. The waste plastic they process will be made of new plastics or other materials; none will be burnt for fuel.
Mura hopes its use of supercritical water for efficient heat transfer will allow them to scale up to industrial levels, lowering energy use and costs. It could be a crucial factor for success where others have failed.
One of the main reasons chemical recycling has failed to take off so far has been a financial collapse. In a 2017 report, Gaia noted multiple projects that had died, including the Thermoselect facility in Germany, which lost more than $500m (£350m) over five years, the UK’s Interserve, which lost £70m ($100m) on various chemical recycling projects, and many other companies that faced bankruptcy.
Financial difficulty is something that has held back not just chemical recycling but all kinds of plastic recycling. “The economics do not stack up. Collecting, sorting, and recycling packaging is simply more expensive than producing virgin packaging,” says Sara Wingstrand, New Plastics Economy Project Manager at the Ellen MacArthur Foundation.
Wingstrand says the only path to “dedicated, ongoing and sufficient funding at scale” for recycling is through mandatory, fee-based Extended Producer Responsibility schemes. These would see all industries that introduce plastic contributing funding to collect and process their packaging after its use. “Without them, it is very unlikely recycling of packaging will ever scale to the extent required,” says Wingstrand.
But Mahon believes a system like Mura’s is another way to shift the balance sheets in favor of plastic recycling by producing an oil that can be sold at a profit. Mura has recently announced partnerships with the plastic manufacturer Dow and Igus GmbH and the construction firm KBR.
“The interesting thing here is that Mura can find value in plastics that aren’t usually economically viable to recycle mechanically,” says Taylor Uekert, a researcher at the Cambridge Creative Circular Plastics Centre, University of Cambridge.
Even with the ability to unmake all types of plastic to be reused again, it is unlikely to make all of the problems with plastic pollution go away. With so much ending up in landfills and the environment, plastic will continue doing what it was made to do – endure.
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