Zero emissions goal: Polymers recycling

Published: 11/02/2021

Zero emissions goal: Polymers recycling

As indicated in the first part of this analysis, the final European goal is to reach zero emissions by 2050.

The main focus of European industry, for the next thirty years, will therefore be: to reduce the environmental impact of its activities.
In particular, it will have to be able to do this by eliminating, or compensating where possible, its own greenhouse gas emissions (starting from the most famous CO2) to allow the European continent to reach a balance between what is released into the environment by production systems and what the environment is physiologically able to absorb.
This is referred to as: “Carbon Neutrality”.

Each company must therefore know where it fits with its process or product, in relation to the European objective. To take this first step, there is a tool already available which is called LCA (Life Cycle Assessment) or, analysis of the life cycle (from the cradle to the grave) of its products.

The tool (or analytical method) allows you to increase awareness of the main variables that participate in the overall production of CO2e in the manufacture of your products.
In other words, it allows to know and in the future to declare, the quantity of CO2e that each product inherits from the production process that generates it.
The LCA calculation is based on objective, quantifiable elements, capable of making visible the areas in which to intervene so as to progressively improve their environmental impact1).

According to the objectives indicated by the EU, the company strategy must also include, for example, the constant search for the best solution that will reduce dependence on fossil energy.

This first step is very important, because it allows you to immediately reduce the “weight” of your traditional production system, while maintaining the consolidated quality of both the production system and the made products.

Examples of this virtuous approach are already visible in the agricultural and livestock production sector.
We also believe that it is important that also the corporate communication and product marketing must begin to consider and make customers aware of the CO2e content, as an added value of each molded part.
This step will also facilitate the end user (your customer) who, thanks to that, will be able to calculate and report the total CO2e value in its technical data sheets and / or on the product’s commercial label2).

It’s easy to imagine that the same information will soon have to be available also in the technical data sheets of the raw materials, in particular of the thermoplastic ones.

Remaining in our sector, the plastics sector, it is already known that plastics have a lower impact (in terms of CO2e / ton) than traditional materials, such as metals, glass or concrete; what is perhaps less known is that when they are recycled, their impact is even lower.

Any plastic material that has finished its life cycle is considered “zero” in terms of CO2e content. When a material is recycled, it brings with it only the CO2e load deriving from its post-processing. Generally this load is equivalent to about a quarter (for some types even less) of the same virgin raw material. [source: shrinkthatfootprint.com]

Thanks to the use of recycled raw materials, it is possible to contribute in two ways to anticipating the achievement of the European 2050 targets: 1) less need for virgin raw materials; 2) lower energy cost to make them available.

Faced with recycled materials, the most frequent question from customers is: ok, everything is fine, we produce less CO2, but where does the technical performance of my products end up?

The search for the best compromise (technical-environmental) is, and will certainly be, a challenge for engineers and designers.
If you want to choose a material in line with the new ecological objectives, and you also want to have certainties regarding its technical performance over time, it will be very important to know also the “useful life” required to your part or finished product
Without forgetting what could be the most likely recovery or recycling path for it.

Constantly aiming at lower emissions, let’s see which solutions and alternatives to virgin plastics are available.

In order:

  1. Plastics (fossils) partially or totally mechanically recycled,
  2. Plastics (fossils) obtained from re-polymerized monomers,
  3. Virgin plastics obtained partially or totally from non-biodegradable bio-based monomers.

What about bio plastics?

Virgin plastics obtained from biodegradable and compostable bio-based monomers are very interesting for their lower environmental impact and for this reason, we will deal with them later when we talk about application segments.

Knowing the life cycle of your product will be important when the choice, for market reasons, or application needs, will fall on bio-degradable – compostable products.

As already stated in other past papers, the world of biopolymers is constantly evolving and aims to compensate for the many technical deficiencies still present at the moment, and limiting their use.

 

The weight of plastics in the various industrial sectors – The sources

Before delving into the world of recycling and its variables, we believe it is useful to take a look at the potential sources of supply of recycled raw materials.
Which are the sectors that consume the greatest quantities of polymers that, reasonably, will return in the availability of the market?

In the graph shown here, although not very recent (2015), it is possible to guess at a glimpse which the most “plastivorous” industrial sectors are.
Each industrial sector among those listed in the graph is currently facing the change towards the circular economy, in a different way and at a different speed.
We believe that the graph can be an excellent indicator framework, useful for the purposes of an overall perception as well as for the objectives of this document.

Of all the industrial sectors present in the graph, in which plastics are the undisputed protagonists, packaging is certainly the most important
It is certainly also the one with the greatest responsibility towards the environment.
Looking at the volumes of thermoplastic polymers consumed each year and knowing the pervasiveness of applications in our daily life, it is therefore no coincidence that it is the segment with the largest number of initiatives on the sustainability, recovery and recycling issue.

Some methods for plastics recycling 

Taking up what mentioned above, recycled materials play an important role in the context of the circular economy for the protection of the environment, which we remember focuses on: reduction, re-use, recycling and recovery.

Wanting to tackle the issue of recycling, but deliberately wanting to remain outside certainly important, but  specific aspects, such as: energy recovery, intelligent re-use of finished products, design for weight reduction, solutions that enhance the physical separation of different materials in an application (topics that we will probably talk about in the future); we can say that everything starts from the good practices of citizens.
This means, from the awareness of a careful and correct separation of waste disposal!

Subsequently, downstream of the collection process, there is certainly the need to have excellent facilities for the selection / separation of waste and good skills and expertise in the regeneration / restoration of the properties of the treated materials: the arduous task of the companies engaged in this important work / service.

On the technological side, it must certainly be pointed out that the machines necessary to carry out each individual task of the regeneration chain, are evolving very rapidly. In recent years, very high-level systems have been designed in terms of production quantities per hour, final quality of the treated product, lower energy consumption, process control and system reliability.
Complex systems that make the recycler’s work simpler, reliable, precise and economically sustainable.         

Mechanical recycling

This is the best known and most widely used system in plastic material recovery plants.
The grinding of the plastic waste produces flakes of variable size (depending on the grids of the mills).
They can be further treated (eg separated by weight or color, etc…) before being sent to an extrusion plant3) .
The complexity of the process depends on the quality and shape of the incoming products.
This varies depending on whether the materials arrive from recovered industrial waste, which very often arrive at the plant already ground, or from post-consumer waste, which instead is composed of products which are still intact.

Materials coming from industrial waste (manufactured goods or warehouse funds) are generally less problematic and more welcomed than post-consumer ones.
Provided that the company that made them available has taken a virtuous approach in the separation and storage phase (which is rewarding in the case of technopolymers), which means for example, separating the waste by type of raw material, by color and contents (e.g. glass fibers, mineral fillers, flame retardant systems, etc…).

Most of these wastes end up in the hands of expert compounders, who are able to restore most of the original thermal, mechanical and aesthetic properties, making them products capable of satisfying the final needs expected by the target market/customer4).
However, it should be stressed that the recycling of transparent materials (eg PC, PS, PMMA) is slightly more complex.
Often transparent products, when recycled, have more marked shades of color (usually gray or yellow) than the original virgin products.

The post-consumer materials, in particular the primary and secondary packaging, arrive at the plants in heterogeneous bales but already divided into transparent materials and opaque materials.
The regeneration of these materials first of all requires a good selection capacity upstream, able to reduce as much as possible the contamination deriving from polymers of different nature (eg the PET from PP or from PVC).
Not to mention the other chemical contaminants, such as liquids contained in the bottles or surface treatments. The process of separation, cleaning and preparation of these materials is therefore more critical.

The variables are greater and they can greatly affect the quality and final cost of the materials.
With post-consumer materials such as: PET, HDPE, LDPE, PP and HIPS, extrusion plants can also play an active role in the elimination of residues (odor, other volatile substances)5) that can affect the quality of the final product and reducing its application opportunities.

Regardless of the origin of the waste (industrial or post-consumer), the extrusion phase always arrives at the end. A step that allows you to obtain granules or semi-finished products.
The granules can have the shape of small cylinders or lentils, depending on the production plant and, in those forms, they can be ready to be reintroduced into the conversion process, the most suited to their rheology (fluidity / viscosity).

Among the most common we can mention: injection molding, blow molding and extrusion.
Or, thanks to ad hoc “regenerative extrusion” systems, the post-consumer materials can go directly from flakes to semi-finished products (films or sheets), skipping the granulation phase.   

Chemical recycling

This process is also referred to as “depolymerization”.

It is a complex process that, in general, breaks down waste materials into basic substances (monomers) and which, subsequently and through ad hoc processes, brings them back to their original condition.
This technique is currently considered the only way to go when dealing with heterogeneous materials that are not easily separable (e.g. coupled), therefore not recoverable efficiently by means of a simple mechanical grinding.

From a performance point of view, the polymers obtained with this process tend to be similar to the original virgin products, therefore in harmony with the guidelines of the circular economy (reduction in the consumption of virgin raw materials, reduction of waste dispersed into the environment).
Research to optimize this recovery process has been ongoing for several years.
In particular on PET from bottles and textiles, but also on PE (HDPE and LDPE) and PP, due to their wide presence in the packaging sector (films, bottles and containers).
However, it is not an easy process. Various factors come into play where balance is not easily controlled: chemical solvents, temperatures, pressures, stability of chemical groups (oxidation), rather long times for the reconstruction of the polymer chain.

The result does not always lead to a completely clean and reusable material in the original process.
It is no coincidence that this technology is widely used to obtain useful by-products for other sectors (oils, modifiers, additives).
One product on which research has really worked a lot is PET.
Numerous solutions have been tested for the decomposition of the polymer into simple elements (Glycol and Terephthalic acid).

Thanks to this extensive research, the first extrusion plants have recently appeared able to depolymerize and re-polymerize the material directly in the machine.
This technology is interesting and will certainly take hold, making a great step forward in the recovery and recycling of this polymer.

In general, there are still some shadows on this technology regarding the real environmental advantage in terms of CO2e / ton. The chemical recycle is a process that tends to require a lot of energy.
However, it should be noted that all the large polymer manufacturing companies have long been committed to this front and we are therefore sure, that all difficulties will be solved over time.

Staying on the subject of reducing emissions, 100% Biobased non-degradable or compostable polymers such as, for example, bioPE and in the future bioPP, play a separate game.

These materials obtained from biomass, or from renewable sources, are no different from their fossil brothers except for the extremely positive fact of having a strong CO2e credit on board.
These are recent materials, that can easily enter the standard production cycles without requiring any changes of the production process and that can be disposed of in the traditional recycling chain.

Also interesting, albeit less advantageous in terms of CO2e, are the hybrid bio-based products.

Even though they are not compostable and not degradable, they have one or more bricks coming from “green” chemistry in their polymer chain and this helps them to have less CO2 on board.
This family includes bioPET,  bioPA, and the bioPC. Obviously, chemical research does not stop and we are sure that soon their “green content” will increase significantly.

 

Conclusion

We have understood that the “bottleneck” of all this recycling activity lies in the ability to accurately select the incoming waste materials. A factor linked to both the system and the education of the population.

The increased availability of recycled raw materials will continue to come mainly from the packaging sector and therefore, will be dominated by the materials used in that segment.

The companies specialized in the production of collection, selection and recycling machinery are increasingly creating high-performance plants capable of making the entire recovery process practical, safe and economical, while also increasingly safeguarding the intrinsic value of each treated plastic material6) .

Downstream of the selection and treatment of waste, extrusion plants are also increasingly evolving towards the “reactive process” (manipulation of the chemical structure during the extrusion phase).

With materials coming from industrial waste, in particular the more technical ones, (eg ABS, PA, PC, PC / ABS), the quality of the recycled material can match that of virgin materials and can be maintained over time (see IQ products).
The percentages of recycled raw material in the IQ mix (industrial quality) can reach> 60%, depending on the needs of the semi-finished or finished product.   

The post-consumer materials (the most available are PP, PE, PET, PS) have a life history behind them which increases the qualitative variables. As these variables increase, the possibilities of reusing them  in the original supply chain are reduced.
In the food packaging sector, or in applications related to contact with food, the possibilities of reusing them in the polymer mix remain quite limited.
Generally, in injection molding the acceptable percentages range from 10% to 15% depending on the application.
On the other hand, in the case of extruded products, in the presence of multi-layer technology, it is possible to reach higher percentages.

Converters in all sectors are looking for new solutions to make packaging lighter, less complex and therefore easier to recycle.
A commitment that will need the best creative resources (designers and engineers) to achieve the goal.

Manufacturers (OEMs) are also looking for easy, cheap and effective solutions to encourage the reuse of finished products (eg refilling).
At the same time, they are experimenting with solutions to regain possession of their plastic packaging, in order to have qualitatively certain materials, to be re-inserted into their production chain.

There is still a long way to go for an efficient circular economy.
But it is an inevitable path that will find more and more technical and technological support from all related industries and financial support from the European Community.

It is clear that also compostable bio-plastics, although for now not very relevant in quantitative terms  compared to their fossil cousins gradually increasing their presence on the market (see previous publication), will soon have to deal with this circular model.

Certainly they will bring a further possible solution for their disposal thanks to their compostability, but they will not be able to withdraw from dealing with circularity as well.

 


Footnotes:

  1. https://www.2milasrl.it/en/lca-how-to-track-sustainable-business/
  2. https://www.osservatorioveganok.com/emissioni-di-co2-in-etichetta-il-caso-oatly-e-la-responsabilita-dazienda/
  3. https://www.2milasrl.it/en/conversion-technologies-extrusion/
  4. https://www.2milasrl.it/en/compound-sales/   The IQ family products of 2Mila are compounds with a variable industrial recycled content according to the needs of the piece and agreed with the customer. 
  5. https://www.luigibandera.com/it/pet-food-film-recycled-flakes/
  6. https://www.sesotec.com/emea/en/lp/varisort-plus As an example of the evolution of systems in support of recycling, see this Sesotec’s “Varisort” line.

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