"There is no one and only solution for recycling"

The future of circular economy in the plastics industry is a complex mixture of mechanical and chemical recycling. Prof. Dr. Manfred Renner, Director of the Fraunhofer Institute for Environmental, Safety and Energy Technology (UMSICHT), describes these technologies as indispensable components of the life cycle of plastics. But what exactly is the role of chemical recycling and how does it compare to mechanical recycling? And how can these innovative processes be integrated into existing value chains?

In an interview with VDMA, Prof. Dr. Manfred Renner delves into this topic and emphasizes the crucial role of politics in promoting the transformation.

Prof. Dr. Renner, what is the task of chemical recycling in the circular economy?

Prof. Dr. Manfred Renner: In the transformation to a circular economy, chemical and mechanical recycling complement each other. It’s not a matter of either/or here, but rather a question of both/and. Both technologies are needed if plastics are to be reutilised as a raw material after usage. There are two main areas of application for chemical recycling: Firstly, when mechanical recycling reaches its limits. For example, when the effort required to sort and clean is too extensive. Secondly, chemical recycling comes into effect when material has already been mechanically processed several times; this is because the polymer chains shorten with each of these reprocessing processes, and additives often accumulate in the recyclate. But if you are looking to generate high-quality material, you need chemical recycling for breaking down the polymer into its components before reassembling it. If you don't do it in this manner, you would have to feed oil-based virgin material into the chain, and you wouldn't get away from fossil raw materials. That is why chemical recycling is an indispensable part of the end-of-life handling of plastics.

The poor energy balance of chemical recycling is often criticised. What is your view?

Renner: You can't criticise the energy balance across the board. The more fractions – meaning different materials – that make up a chemical recycling process, the more separation is needed. Consequently, more energy is required as complexity increases. But that does not mean the CO₂ footprint increases with it. In a research project carried out with the Wuppertal Institute and the Carbon Minds analysis company, we have recently evaluated a pyrolysis process with different feedstocks, and came to the conclusion that the carbon footprint can be reduced by up to 50 percent compared to virgin material.

A study by the Öko-Institut concludes that chemical recycling performs more poorly than mechanical recycling in terms of climate-friendly characteristics.

Renner: There have been an enormous number of studies published on the topic of the carbon footprint of chemical and mechanical recycling, some of which come to completely different conclusions. The only thing is that these contributions are usually not discussed at all. The Öko-Institut study provides the result that some players in the industry need in order to fully discredit chemical recycling. At the moment, a battle is being fought to keep the status quo.

Which method is suitable for which particular application?

Renner: It must be stated quite clearly that there is no rule of thumb for the use of the different recycling methods. We have to approach the subject step by step and try out many things to establish when mechanical recycling makes sense, and when chemical recycling is reasonable. And, when it comes to chemical recycling, we have to try out the different processes to determine which are best suited to which specific polymer mixture; that’s the task we will have to face in the next few years.

So far, most chemical recyclers have been working with polyolefins, which are also easy to process in mechanical recycling. Why are they not looking at more complex plastics?

Renner: Companies are currently going for material streams that provide a realistic expectation of generating profit in the medium term. You don't start with the most difficult materials and invest heavily in plants, without knowing whether you can use them economically or market them. The technology is not the problem; rather, you have to build up capacities and develop the raw material flows step by step. Of course, in chemical recycling you can also process complex material flows and achieve high qualities, but the effort required for fractioning is much higher. And as long as the raw material oil is cheap, this makes little economic sense.

What is the role of politics in this conflict situation?

Renner: We have well-established and highly efficient value chains in the plastics industry. If it is to be transformed into a well-functioning circular economy, this cannot be done without political guidelines. After all, it is a completely new economic system. Now the chicken and the egg dilemma comes into play, whereby politicians don't want to regulate too much, to prevent the market going bust before something new comes along. But a new market will only emerge if there are legislative guard rails in place, because it is not economically self-explanatory. That's where we’re at right now. We have to be aware that the transformation is a process that will take years, if not decades.

What does that mean in concrete terms?

Renner: Here, too, there are no simple rules of thumb. But regulation should definitely be product group-specific. You have to consider step by step what is possible, sensible and feasible for the relevant industry and products, and no specific technologies should be prescribed or favoured either. For example, mechanical and chemical recycling should not be considered separately, but together. This also includes the mass balance procedure. Customer groups that want genuine recycled content must be provided specifically with this plastic. For other - 3 - customer groups, it may be quite sufficient to state on a mobile phone shell that it has been mass-balanced recycled to X percent.

Will the circular economy be a success?

Renner: That depends on the value we place on defossilisation. From a purely economic point of view, it would make more sense to leave highly efficient linear value chains as they are. But if combating climate change is very valuable to us, we must also be prepared to change our behaviour and accept the cost. Implementing the circular economy will cost trillions, but it also offers immense economic opportunities. The various recycling processes, sorting processes, and marking processes are pioneering future technologies – which can be exported internationally as a system. It will then suddenly become a very positive overall concept. You invest, but you will also open up significant international markets. This represents a great opportunity for German companies across a wide range of sectors.