Achema Pulse Highlight Session How Closing the Loop with Chemical Recycling: Potentials and Challenges
To deal with the global plastic waste problem, at great deal of hope is placed in chemical recycling processes. But can the process hold up to these high expectations? An expert discussion at Achema Pulse addressed the potentials and challenges of the technology. PROCESS worldwide listened in on the session and summarized the most important statements for you.
Frankfurt/Germany — Chemical recycling is seen as an opportunity to broaden the base of recyclable materials, at the same time leaving large parts of the chemical processing chain intact as the material enters at a very early point. But does recycling by means of chemical recycling also make economical sense? Will it solve the global plastic waste problem? These are just some of the questions that were addressed in a highlight session at Achema Pulse.
The discussion provided insights into current developments and also compared alternative concepts such as the redesign of polymers to make them more recyclable. Chemical recycling is the (thermo-)chemical conversion of waste fractions containing plastics into basic chemical building blocks, which are then used again for the production of plastics in virgin material quality. As a supplement to mechanical recycling, chemical recycling can be used to open up additional waste streams for recycling which, due to their complexity, have so far mainly been used for energy recovery or, in some countries, also landfilled.
Speakers of the Session:
- Dr. Andreas Kicherer, Director Corporate Sustainability, BASF
- Dr. Bernd Nienhaus, Product Manager, Ekato RMT
- Sander van Donk, Head of Global Technology Business, Sulzer Chemtech
- Prof. Alex van Herk, Principal Scientist — Institute of Chemical and Engineering Sciences A*Star — Agency for Science, Technology and Research; Singapore
Dr. Andreas Kicherer from BASF explained the process of pyrolysis — one type of chemical recycling — in detail. He pointed out that while there are possibilities to sort plastic waste by mechanical means, some waste streams are polluted and many different materials are mixed together. In cases with single waste streams such as PET, mechanical recycling is the option of choice. “But for mixed plastic waste or waste with dirt residues, the recycled end-products are usually not virgin-grade,” Kicherer emphasized. For mixed materials that also contain impurities, paralysis or thermochemical recycling is a possible way to recycle them. In the case of pyrolysis, the plastic is transferred into an oil. This oil can later be used to produced new virgin-like materials that can be used for demanding applications such as food packaging.
Pyrolysis is an efficient process to convert mixed plastic waste into a secondary raw material for the chemical industry. About 70 % of the mixed plastic waste can be converted into pyrolysis oil. According to Kicherer, plastics based on pyrolysis oil can achieve 100 % identical quality to that of fossile-based plastics. “We expect the current 70 % yield can be increased to about 80 %,” he stated.
BASF is already applying this technology with partners that introduced mixed plastic waste. At the moment the company and its partners are using two types of recycled feedstock: Derived from post-consumer plastic waste and derived from post-consumer tires. One plant located in Hungary and one in Germany apply the pyrolysis processes for tires. A Danish partner produces oil from post consumer waste.
Weak Bonds Increase Recyclability
Prof. Alex van Herk proposed a different approach with the material design in focus: “We are working on a platform technology for recyclability and biodegradability.”
- Chemical recycling could be an excellent and broad-ranging alternative recycling method.
- Challenges for all-carbon-backbone polymers are the high energy consumption of the processes and the complex composites of some waste items.
- More efficient chemical recycling routes to building blocks (monomers or macromonomers) for the radical polymers (eg. LDPE, PS, Polyacrylates) in general are lacking.
Recycling of Polymers would be much more efficient if these building blocks could be reconstituted into polymers again, van Herk said. This could be done at lower temperatures, i.e. at room temperature. He outlined the process in brief:
- Synthesis of Cyclic Ketene Acetal Monomers
- Recyclable Polymers via rROP (Radical ring-opening polymerization)
- Formation of Recyclable and sometimes biodegradable products
- Polymer degradation vis Ester Hydrolysis, Purification of oligomers
- Oligomer recycling via recombination
“This is not new chemistry. This approach was developed already in the 1980s,” van Herk pointed out. However, the challenge would be to get these weak bonds evenly distributed into the polymer chain and across the chains. “Our contribution here in Singapore is to improve on this aspect.” According to van Herk, the product is stable and at the same time recyclable — and in some cases biodegradable. To help maked this approach more widely used, van Herk sees the ball in the court of the industry and asked: “Are speciality polymer producing companies willing to modify their polymers in order to make them more recyclable?”
“Industry Partners Have to Work Together”
Sander van Donk from Sulzer Chemtech cited a McKinsey Report stating that by 2030 75 million tons of plastic waste need to be chemically recycled. “This means we need at least 75 industrial plants to treat this plastic. This is a big challenge,” van Donk said. “In Europe 50 % of feedstock of Naphtha cracker will come from recycled feedstock. This shows how much need there is for innovation. These solutions need to be efficient and commercially viable. For this, the industry partners have to work together,” he said.
Dr. Bernd Nienhaus from Ekato RMT also emphasized the need for cooperation: “We are also developing processes together with our partners. We help them scale up ideas from the lab to pilot and commercial plants. There are a lot of thermochemical and pyrolyitc processes being developed. The challenge now is to reduce the energy required for these processes.”
Sanda van Donk added that one of the big challenges was waste collection. “That’s why there are partnerships needed. But also JVs and acquisitions are required in order to ensure availability of feedstock — as we now have in the petrochemical industry.”
The guest speakers agreed that chemical recycling was not the ultimate answer to the plastic waste problem. All available solutions were required to solve this problem. “If there are monomaterial PET-streams, mechanical recycling is by far the most effective and cost-effective one — and also from the environmental point of view”, said Kicherer. But also changes in behavior would be important to avoid plastic waste in the first place.