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By 2030, 55 % of plastic packaging waste in Europe must be recycled. In Flanders, the aim is to even achieve a recycling rate of 70 % for household waste. Today, we are still a long way from achieving these goals, and so waste processors, chemical companies and knowledge organisations such as VITO are stepping up their efforts. In the context of the four-year Catalisti project WATCH, innovative chemical recycling of various types of plastic waste into basic raw materials of plastics and high-grade chemicals is underway.

Despite selective collection and large-scale sorting, today only 30 % of plastic packaging waste from households in Flanders is recycled into new plastic. A similar percentage applies to packaging waste in general. The vast majority of that waste is therefore given an unsustainable, non-circular destination: it is dumped in landfill, incinerated or exported to countries outside Europe. 

So we need to do better. But is that possible? Today, plastics are recycled in two main ways', explains Brecht Vanlerberghe from VITO. 'With mechanical recycling, the waste is remelted into plastic pellets, which are then returned to the industrial chain. However, this is only possible if the plastic waste is of good and certified quality'. However, the resulting plastic applications are typically inferior – hence the term downcycling. 'In a variant of this recycling, undesirable substances are first removed from the plastic waste using solvents, allowing the plastic to be used again for the same applications – this is then called upcycling. However, recycling in this way is only possible if the initial waste stream is sufficiently pure.'

Preferred by the chemical industry 

An alternative is that the plastic waste is broken down into its building blocks and then reassembled. Vanlerberghe: ‘This is called chemical recycling. Polyethylene terephthalate (PET), for example, is broken down into ethylene glycol and terephthalic acid, impurities are removed and it is converted back into PET. With polyolefins, the plastic is broken down into a kind of naphtha, which can replace fossil naphtha in existing crackers and thus re-enter the plastic chain'. This is also how the chemical sector sees it: it has a clear preference for chemical recycling. 'Unfortunately, today's techniques require us to know exactly what types of plastics are in the waste. To get around that problem, the WATCH project was launched'. 

WATCH (WAste plastic To CHemicals by pyrolysis) started in 2019 and runs until 2023; this project is supported by VLAIO and coordinated in organisational terms by Catalisti, the Flemish spearhead cluster for chemistry and plastics. This project examines the chemical recycling of four types of plastic waste: mixed polyolefins, multi-layer packaging plastics, polystyrene (PS) and polyurethane (PUR). The aim is to convert the waste in an innovative reactor into various basic chemical raw materials - for the manufacture of plastics as well as high-grade chemicals - via rapid pyrolysis (chemical cracking at very high temperature in an oxygen-free environment). One of the most important end products is naphtha, i.e. the basis of plastic production. 'This is a new technique for chemically recycling plastic waste," explains Wannes Libbrecht, Project Manager at Catalisti. 'If we want to significantly increase the recycling rate, we have no choice but to look at new techniques. But we also need to look at the chemical sector in particular for solutions, because in the end it will have to work with the end products from recycling'. According to Libbrecht, pyrolysis technology is highly promising because the end products have many applications and are therefore of interest to industry. 'They form the basis of chemicals such as olefins, resins, aromatic compounds, styrenes and diols, as well as fuels'. 

More energy-efficient recycling process 

The various partners in the project each have their own focus. For VITO, this is primarily the separation and purification of the plastic oil obtained after pyrolysis. We investigate how we can make maximum use of our innovative membrane technology in these separation processes,' explains Pieter Vandezande from VITO. 'Before pyrolysis, during the decontamination of the waste, but especially afterwards, during the separation of products such as naphtha from the oil obtained'. At VITO, they believe that membrane separation provides a significantly more energy-efficient recycling process than current separation techniques. 'That is of course very important, because one of the main reasons why we recycle is to reduce CO2 emissions'. 

Researchers from Ghent University (who are coordinating the project in scientific terms) are in charge of pyrolysis, while their colleagues from KU Leuven are in charge of catalytic reprocessing. So all this will be done in an innovative reactor that has yet to be developed and built. 'This is about strategic, exploratory basic research', according to Roel Vleeschouwers from VITO. 'Experimentally, we mainly work on a lab scale, and we hope we will soon be able to produce a few litres of naphtha. The scaling up, for example in the form of an industrial pilot installation, is for a possible follow-up project'. 'We are starting at the start', confirms Vandezande. 'The aim is to build up our knowledge about chemical plastic recycling via pyrolysis. But as VITO, we also want to use this project to position ourselves in this emerging domain'. 

Broad advisory council 

The chemical and recycling industry is now watching with interest, with a view to its plans for the near future. For example, within its own Plastics2Chemicals project (P2C), waste processing company Indaver envisages several recycling plants over the next ten years, including facilities to convert plastic waste such as PS and polyolefins into chemical building blocks such as naphtha, styrene and wax. 'Breakthroughs in chemical recycling being investigated within WATCH can mean an extra step in increasing the yield and efficiency of our process, resulting in a significant improvement in our P2C business case', says Erik Moerman of Indaver. In the very short term, Indaver is planning a demo plant for the chemical recycling of polystyrene and polyolefins. 'A successful start-up of this demo plant at our Antwerp site will be a first important step in redirecting plastic waste towards innovative large-scale recycling applications'. 

Indaver sits on the advisory council of the WATCH project, together with around ten other waste, recycling and chemical companies. As such, the companies can exchange their experiences 'from the field' with the researchers. INEOS, one of the world's largest plastic producers, also sits on the council. 'As a world leader in the production of styrene, we focus strongly on making our product portfolio more sustainable,' explains Michiel Verswyvel of INEOS. 'Within the WATCH project there is time to consider more fundamental research - the chemical recycling of polystyrene into styrene monomer - which in turn leads to more advanced insights. This is something that is not always possible within the industrial environment'. 

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