The Chemical Recycling Solution
Resource efficiency, climate change, waste management, and especially plastic waste – just a few of the issues that have a connection, making global business complex beyond expectations. What is clear is that something has to change. Foreseen growth demand of materials will cause scarcity in raw-materials, and that requires us to consider advanced methods, also to recycle and reuse existing materials instead of creating everything from new virgin materials. There are also many country and regional regulations regarding recycling targets. On the other hand, consumers are also guiding businesses towards the usage of recycled materials. Solving these challenges requires new innovations and strategies across the value chain.
But how to deal with existing plastic materials, from feedstock to refining and end use, utilisation of side and waste streams. The precise questions and practical solutions need to be identified.
The plastics recycling route is complicated and not without challenges. Different plastics grades usually do not mix, and even a small amount of the wrong grade may pollute the whole stream of another. Plastics require appropriate collection and sorting. Multicomponent plastics recycling through mechanical or chemical means is either not yet possible, extremely energy intensive or too costly. Thus, new technologies and regulations need to be developed to improve recycling rates.
Chemical recycling is emerging as a main candidate. Chemical recycling is a family of technologies that enables a major shift towards highly efficient circular material economy. The main focus in chemical recycling is in plastics, but chemical recycling may also find its uses in other material streams.
'THE PLASTICS RECYCLING ROUTE IS COMPLICATED AND NOT WITHOUT CHALLENGES'
Today we are aware of some recycled plastics products. The quality of recycled materials is expected to improve as technologies are developing all the time. Mechanical recycling requires intense sorting according to plastic type, followed by washing and regranulation. Sorting is typically done by near infrared, middle range infrared or magnetic flotation techniques. In practice, all plastics can be recycled mechanically, yet plastics like polyethylene, polypropylene and PET are the most convenient. In the recycling of industrial clean grades, the final recycled plastic is very close to the original due to minimal contamination. In post-consumer resins (PCR) the collected plastics contain remainders of food, soil and chemicals and so the quality is not uniform, leaving the end product grey and often with an odour.
The limitations of mechanical recycling have led to the development of chemical recycling techniques, many of which already exist today. For example, for PET recycling techniques include the disintegration of the polymer back to monomer or oligomers that can be polymerized again into plastics. Other techniques include hydro-pyrolysis, pyrolysis followed by catalytic hydrotreatment, thermal (catalytic) cracking, gasification, Fischer-Tropsch, selective solvent extraction, and so on. Some of these technologies are also suitable for turning mixed waste, biowaste and waste from agriculture and forestry into hydrocarbons which can be used as feedstock for plastic production.
We estimate that a large scale of 50% of plastics can be recycled mechanically, and 50% would need chemical recycling. Mechanical recycling also leads to the gradual degradation of the polymers as the chains are cut shorter. Chemical recycling, however, going back to the hydrocarbons and monomers, is capable of recovering all the properties of the virgin plastic.
DOWN TO EARTH: FROM COLLECTION TO RECYCLING
To implement strategic choices, a series of often locale-dependent questions have to be answered. A short look at collection, sorting and separation and recycling illustrates this.
How are plastics collected? All plastics are valuable, no matter how long they have been in use and no matter what type and quality they represent. The collection of plastics needs to be well organized, planned and implemented to enable full collection. The plastics found in nature, seas, oceans, and on land as litter need completely different systems from e.g. plastics from packaging, automotive and construction. Likewise, the geography, culture and habits of different regions, also in Europe, require different measures. Is some deposit scheme needed to support the collection?
- SORTING AND SEPARATION, PRE-TREATMENT AND POST-TREATMENT
The separation of plastics and the different plastic types can be done at source, or not at all. Pre-treatment processes vary depending on the process chosen. The quality and the range of different polymer types and the recycling processes used determine the need for other additional measures.
- MECHANICAL RECYCLING
Although all plastic types can be recycled mechanically, it is only suitable up to a certain point. Mechanical recycling is typically considered as a low capital intensive investment, however, the scale is limited due to the intensive need for pre-sorting of plastic types. Even then, there are often impurities left in many products.
- CHEMICAL RECYCLING
There are already several suitable chemical recycling technologies depending on the purity, quality and bio-based content. Pyrolysis, hydropyrolysis, thermal cracking, gasification, solvent extraction, hydrothermal liquefaction and other techniques can convert polymers back into hydrocarbons, oligomers and monomers suitable for conversion back into plastics.
Some of the processes can be highly energy efficient, using part of the feedstock as an energy source and still providing excess heat for district heating. The most important factor is that chemically recycled plastics have the same quality and properties as virgin plastics.
DISRUPTION ON THE HORIZON
Chemical recycling is a disruptor as it enables recycling of even mixed and dirty plastics without compromising quality and performance. It can enable shortcuts in processes via depolymerisation or physical solvent extraction, or even changing polymer type during recycling e.g. from polystyrene to polyethylene.
The processes are largely known chemical and petrochemical processes, but yet require intensive scaling-up for this purpose. The scale-up here means both larger units, but also a large number of decentralised small units depending on the area, logistics options and amount of waste plastics available. This change in business model or “mapping” of units is another potential disruptor.
AFRY can provide services for the entire sustainable business process from conceptual studies and strategy, all the way to commercial production and new recycling sites, or the modification of existing ones.