Chemical Recycling of Plastic Versus Mechanical Recycling?

The history of plastic recycling was born and developed, to date, thanks to the mechanical system, made up of selection, grinding, washing and extrusion of polymers that constitute new raw material.

This type of recycling leaves behind a considerable amount of non-recyclable plastic waste that goes to incineration or landfill.

We have addressed the reasons for a quantity of non-recyclable plastic waste several times in the blog articles of the rMIX portal, but today, as presented by Sreeparna Das talking about the ENI-VERSALIS chemical recycling process, we can see a concrete possibility of finding the right placement of plastic waste that cannot be recycled through chemical recycling.

Competition with mechanical recycling? I would say no, indeed I see a completion of the circular waste process.

The resistance of plastic, considered a benefit in the past, today takes on a strongly negative connotation. Now, when we hear the word plastic, one of the first images that comes to mind is that of a bag floating in the ocean. This is largely due to the unprecedented increase in single-use products and the disposable mindset of consumers.

What are the advantages and disadvantages of plastic?

It is important not to lose sight of the value of plastics and the various industries that depend on this material. Plastic has proven its advantages in terms of mechanical properties, performance, versatility, cost, etc.

It is, for example, a fundamental material in the fight against the pandemic of COVID-19 around the world. The risk to health, especially for medical professionals and frontline workers, would be greater without the plastic present in PPE kits, masks and gloves.

How plastics are currently produced, consumed and handled at the end of their life, however, is not completely sustainable. The debate on replacing plastic with other recyclable materials, such as paper, especially in packaging, has taken hold due to the negative impact on the environment of linear plastic production, the high volume of single-use applications and the mishandling of waste over time Some years.

The circularity of plastic and the valorisation of waste are the order of the day and chemical recycling technologies can play a fundamental role in achieving the same goal.

The recycling of plastic

Clearly a change of course is required. Those who work within the plastics value chain must adopt circular principles. Part of the solution to ensuring plastic's circularity is its recycling, but current rates are far from ideal.

The European Commission recognizes the need for higher recycling rates in its recently adopted action plan for the circular economy under the European Green Deal .

Member States must achieve the following objectives:

• 55% recycling of plastic packaging waste by 2030

• Reduction of consumption to 40 bags per person by 2026

• Improve product design to meet durability, repairability and recyclability requirements

• Monitoring and reduction of marine litter

Many stakeholders are following the circular model of the Ellen MacArthur Foundation and in in this direction, Eni's circular strategy focuses on:

• The use of sustainable raw materials

• Reuse, recycle and recovery

• Extend the useful life

To further support the circularity of plastic and increase recycling rates , Versalis started the Hoop® Project in February 2020. The project focuses on the development of new technologies for the chemical recycling of plastic waste.

Together with Research and Development Services (SRS), the chemical company of Eni is developing a process for the valorisation of waste mixed plastics that cannot be mechanically recycled.

What is the chemical recycling of plastic?

Chemical recycling, an umbrella term for several advanced technologies, can transform plastic waste into raw materials that fall into the value chain to produce new polymers. CEFIC, the European Council of Chemical Industry, has broadly classified these technologies into three types.

Chemical recycling and classification of technologies.

Dissolution : from plastic waste to polymer

The process consists of extracting the polymer by dissolving the selected plastic waste with a solvent and / or heat. In this way it is also possible to separate the additives from the polymers. Furthermore, the extracted polymer can be processed with new additives to produce new plastics.

Depolymerization : from plastic waste to monomer

This method involves the selected plastic waste being broken down into their constituent monomers using various chemical reactions. The purified monomers can then be used to produce new polymers. The most suitable polymers for this technique are polyethylene terephthalate (PET), polystyrene (PS), polymethyl methacrylate (PMMA), etc.

Conversion : from plastic waste to raw material

Thanks to these techniques, mixed plastic waste can be converted into a hydrocarbon blend that can be used as a raw material for new plastics. This raw material similar to oil or gas can replace the fossil raw material just extracted in chemical plants. The two main types of processes are: pyrolysis and gasification.

Pyrolysis is one of the main processes explored today to achieve the challenging recycling goals and meet the need for plastic circularity.

The process takes place at high temperatures (in the absence of oxygen) and transforms plastic waste into raw materials that are further used in the production of new chemicals. Versalis is pursuing the development of pyrolysis technology through the Hoop® project.

To better understand the mission and vision of the project, I spoke with Fabio Assandri, Director of Research and Technological Innovation of Versalis.

D: Can explain Hoop® and why is Eni investing in this project?

Assandri: Today, plastic waste is a challenge for all of us. Europe collects nearly 30 million tons of post-consumer plastic waste and recycles only a third of it. Mechanical recycling is the main method used and efficiently manages pre-sorted waste streams (e.g. single material, less contaminated, etc.). A good example is PET water bottles.

However, mechanical recycling has some limitations. The reprocessing steps lead to degradation of the material properties and can cause a reduction in transparency. It also includes on the number of times plastic can be recycled. Perhaps, however, the biggest drawback is the inability to manage more complex and mixed plastic waste streams, which are currently incinerated or landfilled.

This led us to invest in the Hoop® project, a project that focuses on chemical recycling as an alternative solution to the problem, thus advancing the circularity of plastics.

D: How does Hoop® work?

Assandri: Hoop, the name of the project, it represents a complete circle and therefore symbolizes support for circularity. We worked on a new process based on the SRS pyrolysis technology. which transforms polymers into smaller molecules and bricks. This conversion is analogous to disassembling a lego set into single pieces.

We have completed the pilot tests and also the design of the demonstration plant with a capacity of 6,000 tons per year at the Mantua site. Our goal is to scale and have the technology ready for large-scale application.

Q: What is plasmix? And what are the advantages of pyrolysis technology?

Assandri: Plasmix is the mixed plastic waste that is not suitable for effective mechanical recycling. It represents a significant percentage of plastic waste that is currently not recycled.

Pyrolysis is ideal for such disposal streams and allows materials to extend their use, in line with the principles of the circular economy. As the quality is the same as virgin plastics, chemically recycled grades can be used in high value applications, including food contact applications.

The process we have developed offers further advantages such as flexibility, energy efficiency, product quality and great savings in greenhouse gas (GHG) emissions . The recovery of the materials of all flows resulting from the pyrolysis process (liquids, gases and solids) is an absolute priority for us.

Q: Can chemical recycling reduce dependence on fossil fuels and CO2 emissions?

Assandri: Overall, the ecological footprint of chemical recycling is lower than the emissions upstream and downstream of the current linear system (extraction of raw materials, plastic production and end-of-life waste management).

Currently, mixed plastic waste is being incinerated or landfilled. Both solutions have a negative environmental impact. Incineration leads to increased emissions of CO2 and other pollutants, while landfilling causes further dispersion of plastic waste into the environment.

Chemical recycling avoids these problems and, by converting waste back into raw materials, helps reduce dependence on fossil reserves.

Q: Will mechanical recycling vanish with the development of chemical recycling plants?

Assandri: Not at all. Mechanical recycling is already a considerable activity with a well developed ecosystem for polymer streams such as PET, HDPE, PP, etc. There is no point in replacing existing systems that work well.

The aim of the project is to integrate mechanical recycling and drastically improve the circularity of plastic products, expanding the scope of recyclable waste streams. In fact, I believe that mechanical recycling will benefit from the development of chemical recycling technologies, as goals and ratings would be more split between the two.

Q: Is Hoop® the solution to the problem of plastic waste?

Assandri: The issue of plastic waste is complex and requires a multi-layered approach to find effective solutions. Projects like Hoop® are taking steps in the right direction and are an important part of the solution. Whether or not chemical recycling, together with mechanical recycling, will be able to tackle the problem of plastic waste depends on several factors:

All actors in the value chain, including brand owners, need to be involved and collaborate.

Consumers also have an important role to play in following proper waste collection and in increasing demand for recycled products.

Standardized and internationally recognized certifications are a necessity. As chemical recycling generates an equivalent virgin raw material, the materials mix in chemical plants and make it difficult to physically trace the recycled raw material. Experts therefore suggest using the mass balance approach to accurately track the flow of recycled material around industrial facilities in order to attribute the correct value of the recycled content to a product.

One last aspect, but no less important: the industry will also need political and regulatory support. Greater clarity on sustainable plastics production is expected to come in early 2021, once the European Commission completes the revision of the EU Taxonomy Regulation.

Automatic translation. We apologize for any inaccuracies. Original article in Italian.