Over one billion waste, or end-of-life tyres (ELTs), are generated around the globe each year; 55 million of these are produced in the UK. Since a ban on placing tyres into landfill came into force in the UK in 2006, the tyre recycling and recovery sector has become big business.
Many of these are exported to other nations or burned, while others are used in cement production or for sports pitches. However, there are simply too many tyres to process in these ways.
The leading process for dealing with ELTs in an environmentally responsible and entirely circular way is pyrolysis. Pyrolysis is not a new process; it has been used in numerous ways for centuries, and more recently in trying to reverse-engineer certain materials from virgin oil since the 1950s. However, it has only become viable in the past few years.
Pyrolysis is a chemical process, where the ELTs are heated without access to oxygen, so the oxidation process only occurs in an extremely limited measure. This can be achieved, for example, through a nitrogen atmosphere, by vacuum, or by passing pyrolysis gases in a counter current through a reactor.
The process divides the organic material in the old tyres, and creates gases, oil, steel and coke made of carbon, which can be processed into carbon black. The most common use of carbon black is as a pigment and reinforcement in car tyres. It also helps conduct heat away from the tread and belt area of the tyre, increasing tyre life.
Olivier Lepez, founder of France-based ETIA, says: “2003 was the year we installed the first pyrolysis plant in France. Since then, we have developed pyrolysis equipment and applications which we also manufacture and sell to other companies.”
In 2019, France-based ETIA became a subsidiary company of Norwegian waste recycling company Vow ASA, and Lepez its chief innovation officer. The company has a range of applications in which pyrolysis is used to convert biomass, plastic waste, ELTs and sewage.
The process
For ELTs specifically, the process begins when pre-prepared granulate is fed into processing equipment (pictured above). Adds Lepez: “Next, we select the operating conditions (temperature and time) depending on what we want to produce. We have a patented, unique reactor using proprietary technologies where we use a patented electrical heating screw conveyor where the pyrolysis process produces recycling carbon black and high energy syngas (synthetic gas), which can be used as a fuel or cooled to produce pyrolytic oil (bio-oil),” pictured above, inset.
Meanwhile, the UK is about to get its first continuous pyrolysis plant for ELTs. Carlton Forest Group, based in Worksop, is about to open its plant – the PACS Series 1 – which will be capable of processing per hour one tonne of tyre crumb (tyres which have been de-fluffed, de-wired and chipped) from passenger vehicles. From this it produces 500 litres of tyre pyrolysis oil (TPO), 380kg carbon char – which can be further milled into recovered carbon black – and a residual syngas which can be used to heat the reactor instead of using additional fuel. Excess heat from the process can also be recovered through an axial steam engine to produce electricity.
Carlton Forest Renewables’ business development manager Warren Steele says: “As a core logistics company, Carlton Forest started to demonstrate a problem in terms of disposing of its own tyres sustainably from its fleet of 50 vehicles. It became a point of interest for our CEO, Mark Pepper, to find a sustainable solution.”
Pepper acquired a South African business called IRR Manufacturing, which builds pyrolysis equipment. Naturally, Steele says, a sustainable disposal solution became a commercially attractive one which it, like Vow/ETIA, uses not only for its own operations but also sells on to third parties on a joint venture partner basis.
“At our plant in Worksop, we have two kilns and one oxidiser and then a series of pipework that manage the condensing and non-condensing gases,” explains Steele. “The non-condensing gases recirculate as a syngas within the process to help power the plant on a standalone basis. In isolation, we can fire up the plant using LPG, meaning we can sustainably run these plants through their own gas recirculation in any remote location; Australian coal mines, in the desert, or in non-infrastructure rich countries in Africa, for example.”
The PACS Series 1 plant, pictured p10, is not fully automated: it still requires 4-5 people per shift operating the control room, the PLC and maintaining temperatures and the feed system.
OIL PRODUCTION
Typically, producing one kilogramme of carbon black requires between 1.5-2kg of oil. However, with pyrolysis, it is possible to reclaim the carbon black from existing tyres and reuse it.
TPO produced during pyrolysis can be sent for further refinement or straight into the marine gas/oil industry, though Steels says Carlton Forest is talking to large petrochemical companies that are interested in processing it into commercial products. Lepez adds that TPO is being used more often as a feedstock for steam crackers which break down saturated hydrocarbons into smaller, often unsaturated, hydrocarbons in the chemical and oil and gas industries.
According to Lepez, Vow/ETIA’s process, which also processes up to one tonne per hour, requires 300-350kWh per tonne, depending on the product being put through pyrolysis. Though some of this energy, (if not all in Carlton Forest Renewables’ case), is provided by the recirculation of syngas back into the plant to heat the kiln, for treating of producing electricity for the system itself through a gas engine.
In addition, Carlton Forest has recently added a steam engine to its plant which creates electricity via recirculated syngas.
MEETING CHALLENGES
One of the biggest challenges of the production process, Lepez says, is being able to generate the best quality carbon black, which means fine-tuning the operating conditions of the plant to produce the correct specification of recycled carbon black for the market it is to be sold in.
“If you want to sell the product at a price which is acceptable for your return on investment, you need to make sure you provide the right quality that the market needs,” he says. “This is where we focus our knowledge and skills.
“How the feedstock is prepared in the first place makes a difference,” he adds. “After that, it’s a question of operating conditions such as temperature and time, and you need to be very, very precise on that.”
But the biggest challenge of all that pyrolysis could solve is the problem of waste tyres going to landfill. Will this process do away with this when adopted on a more mass scale?
“I think the answer is probably yes,” says Steele. “The challenge is that every person within the pyrolysis sector is looking at the other person in the pyrolysis sector. Everybody is super-secretive rather than being collaborative. We don’t want to be secretive, which is why we enter into joint ventures with third parties; we’re quite keen on spreading the love on this.
“Ultimately, how many people are going to come to the party? Those that can afford to put the solution in place. Those are the companies we want to work with to create sustainability in the grand scheme of things.”
Pyrolysis may not be the only solution to eradicating ELTs from landfill, but it is the solution that is at the forefront of the market right now and it is proven in use in Europe and South Africa.
Additionally, Lepez says: “The market for recycled carbon black seems to be much larger than we can produce. Now we need to deploy and launch the technology to convert people to choose this technology. Therefore, it is important to develop the technology to produce an industrial product of guaranteed quality.”
Carlton Forest claims that one PACS Series 1 plant will produce over 3,000 tonnes of recycled carbon black a year, negating the production of new carbon black, which is estimated to save around 8,000t of CO2 per year, which will help theUK reach its net zero carbon goals.
BOX: TYRE PYROLYSIS NEWS
The EU-funded BlackCycle collaborative research project, which runs until 2023, has processed used tyres and produced 60,000 litres of optimised pyrolysis oil. That material reached the Spanish project partner Sisener Ingenieros SL on 24 May 2022. The next step is the distillation of the oil, which is then processed by Orion Engineered Carbons into sustainable carbon black (sCB) and is intended to be used by Michelin in new tyres. The sCB is said to have identical characteristics to conventional carbon black of the same quality.
Elsewhere, Scandinavian Enviro Systems (Enviro) has received approval as an intermediate for its pyrolysis oil according to the EU chemicals regulation REACH, and therefore will now execute a previously-announced order for pyrolysis oil worth SEK 2m (£161,000) to a US oil company. The approval means that Enviro can sell up to 1,000 tonnes of pyrolysis oil per year, but the company is applying for REACH approval for the sale of unlimited volumes.
Enviro says that the approval is an important first step towards the commercialisation of pyrolysis oil, since it means that it can begin larger production tests of the oil.
REACH approval also provides a step towards circularity, because it means that the company considers its pyrolysis oil to have achieved ‘end of waste’ criteria, meaning that it no longer needs to be handled as waste.
In other news, the company has been granted an environmental permit for a planned recycling plant in Uddevalla, southern Sweden. The facility will have the capacity to process up to 60,000 tonnes per year, which would suffice for the recycling of more than 60% of Sweden’s total annual volume of end-of-life tyres. A final decision on establishment of the new plant has yet to be made, and the company says it depends on several factors, such as securing access to end-of-life tyres and agreements covering deliveries of recovered materials.