Creating a circular PVC chain is within reach, now that Groningen start-up Cescco2 can continue to scale up a new PVC upcycling technology using supercritical CO2 (scCO2). “It is the only green technology in the world for recycling PVC”, says Francesco Picchioni, professor of Chemical Engineering at the Rijksuniversiteit Groningen (RUG). This project has been awarded a subsidy of €2.5 million from the Just Transition Fund (JTF).
– Pierre Gielen
PVC, or polyvinyl chloride, is the third-most used plastic in the world, after PE and PP. Approximately 100 million tons of ‘virgin’ fossil PVC are produced annually, which is around 18% of all plastics worldwide. It is found, for example, in pipes, window frames, cables and floor coverings. However, only 1% of PVC is currently recycled, compared with 20% of PE.
The recycling of PVC is hampered by impurities, such as PE, rubbers and metals. For example, old PVC often contains lead as a stabilizer, which is no longer permitted today. Furthermore, PVC products contain toxic plasticizers, the so-called phthalates. Separating the individual components of PVC according to the traditional method requires organic (toxic) solvents and heating the PVC.
However, when heated above 150 degrees Celsius, hydrochloric acid (HCl) is released. This is highly caustic, very corrosive and destroys the equipment. In the event of a fire, highly toxic dioxins can also be released into the atmosphere, as happened in Italy in 1976 during the infamous Seveso disaster, which left thousands of people dead. This was the reason for new EU legislation on harmful substances. “PVC is one of the most dangerous polymers in the world”, concludes Picchioni. “Using supercritical CO2 for extraction in combination with extrusion solves all these problems in one go.”
Most people know CO2 simply as a (greenhouse) gas. However, it is a molecule with very interesting properties. By heating it and pressurizing it, it can change into a supercritical state, somewhere between gas and liquid. In this state, it is ideal for use as a non-toxic solvent in which chemicals dissolve into a mixture. This also applies to PVC and its additives – even at temperatures well below 150 degrees Celsius. When the pressure is released, the CO2 evaporates completely and only the dissolved substances remain.
The principle has been used for decades to decaffeinate coffee beans. The pressure required for this (73 Bar) could only be achieved with heavy pumps which were a high cost. This made working with supercritical CO2 unfeasible for smaller companies for a long time. However, since prices have fallen considerably and European regulations have limited the use of environmentally harmful organic solvents, demand from the business community has grown as to the possibilities of this technology.
In 2017, at the request of Francesco Picchioni, Klaas Zijlstra of ASQA Subsidies brought together a consortium of 15 companies and the RUG to jointly investigate these possibilities in a Knowledge Centre for Supercritical CO2. For this project, under the name Industry 2030, the SNN (Northern Netherlands partnership) and the Province of Groningen made €4 million available.
Hendrik Wolters, director/owner of TRH Recycling in Emmen, read about this initiative and had the idea of using supercritical CO2 for the recycling of PVC cable waste from telecom cables. The idea was investigated by four students and a test setup in Professor Picchioni’s laboratory and resulted in a promising ‘proof of concept’ for which an international patent has been applied.
The new upcycling technology combines various extraction methods, such as melt filtration, the use of scCO2 and extrusion. This makes it possible to separate the PVC from both solids and plasticizers as well as other additives, including pollutants of very high concern (SVHCs, POPs).
The composition of PVC from residual flows can vary greatly, depending on the original application. According to Picchioni, however, it makes little difference to the process whether sewage pipes, cables or floor coverings are put into the reactor. “If the PVC is mixed with rubbers, metals or other polymers, we do have to adjust the extrusion accordingly, but these are minor adjustments. The essence of the process remains the same.”
The further development of the new upcycling method is housed in the start-up Cescco2 BV, loosely named after Francesco Picchioni. Cessco2 will work on scaling up the technology, together with consortium partners RUG, ASQA Subsidies, Prysmian Netherlands BV and Deepgrooves BV, and will continue to look for new partners. Discussions are also taking place with various international PVC manufacturers, including the Japanese Shin-Etsu Chemical, the largest PVC manufacturer in the world in terms of volume.
Henk Emmens (Groningen executive member for, amongst others, economy, agriculture and nature) says he is pleased with the JTF subsidy being awarded to the PVC upcycling project: “This is exactly the type of innovative projects that suit the JTF. This European fund is intended to stimulate economic activity in regions that are disproportionately affected by the phasing out of fossil energy. In the Northern Netherlands, it focuses on the greening and sustainability of SMEs and the chemical industry, while retaining existing and developing new employment.”
The JTF focuses on complex and large projects with a turnover of several million, in which companies collaborate with a knowledge institution. “There is a reason why you have to invest heavily in alliances of companies,” says Emmens. “It is simply too much for an SME entrepreneur alone. Seeking cooperation is also the intention of the knowledge and valorization projects. That is a huge exercise and you also need specialists for that. ASQA is one in the Northern Netherlands that is good at that.”
Francesco Picchioni: “It’s great to see everyone taking on a role in this: one the entrepreneur, the other from science and the third brings the parties together and has knowledge of subsidies.”
In addition to upcycling, the project ‘PVC upcycling with supercritical CO2’ includes the development of new recycling technology because there is a limit to upcycling. “After a lifespan of 20 or 30 years, we can give PVC a new life of perhaps another 20 or 30 years, until a point is reached where the quality has become so low that it can no longer be upcycled,” says Picchioni. “I hope that point is only reached after five steps, but it depends on the circumstances in which the PVC is used.”
Two technologies will then be considered for the final end-of-life solution: conventional chemical recycling using a modified pyrolysis process, or biochemical recycling using enzymes. The latter is still in its infancy and is mainly an idea for the longer term. Pyrolysis is already a common technology in which materials are heated to high temperatures under pressure and without oxygen. The RUG has developed a method to prevent the release of HCl, which will also be patented soon.
The next step that the consortium will take is to build a new lab-scale setup to investigate how the upcycling technology with supercritical CO2 can best be scaled up. This phase will be completed by the end of the summer of 2024. After that, a pilot plant will be built in Groningen with a capacity of 200-300 kg per hour, which can be operational within one to two years.
According to René Langevoort, one of the initiators of Cescco2, this will also enable the first commercial production to be run. The ultimate aim is to design upcycling lines with a capacity of approximately 1 ton per hour that can be installed in existing PVC factories, or stand-alone. “This could potentially create a completely new industry.”
The technology could very well be sold under licence for implementation elsewhere in the world. “We do not need to worry about the material flows drying up. All PVC that has ever been produced in the past 50 years is still floating around because of the idea that nothing can be done about it. So there is enough PVC available.” Moreover, the technology of supercritical CO2 as a green solvent is not exclusively applicable to PVC but can also be applied to other polymers and in other industrial sectors.
“This project can therefore serve as an example for others”, says Klaas Zijlstra. “We want to involve many more companies in this, meaning actively searching for new consortium partners and working on forming and expanding the collaboration.”.
Companies that want to join the consortium or want more information can contact Klaas Zijlstra of ASQA Subsidies or René Langevoort of Cescco2 B.V.
This article was created in collaboration with ASQA Subsidies, Rijksuniversiteit Groningen and Cescco2 B.V.
This article originally appeared on: Argo&Chemie
