How to Transform Plastic Waste into Products?


Plastic waste comprehends a wide range of materials, and it comes from different segments of the economy. In Europe for instance, there are seven main economic activities which demand plastic and therefore produce plastic waste, therefore, revaluing plastic involves several types of it and material streams vary widely. These main activities are presented in Figure 1 in the description section.

There are two main methods to transform plastic waste into revalued material for new products manufacturing, one is through a mechanical processing and the other using chemical processes. After the first stages of the plastic revaluation scheme, i.e., after recovering the material from any of the sources available, mechanical and chemical processing are the next step to obtain actual workable materials.

In this Knowledge Unit, a brief description of plastic waste composition is given, alongside with and introduction to mechanical and chemical processing. A more detailed analysis of the composition of plastic waste will be developed in another Knowledge Unit.


As mentioned before, a fair picture of plastic waste composition can be obtained by looking at the plastic demand of new products. Figure 1 shows this demand segregated by economy segment and by polymer type.

As it can be seen, the use of plastic by packaging industry outruns the rest of the sectors by far margin. Not only packaging has a shorter lifecycle in comparison with the rest of plastic waste types, but also, it is one of the hardest type to revalue. The wide range of containers and packs for branding and marketing purposes reduces reusability and recyclability [2], aside of that, Post-Consumer (PC) revaluable plastics are often contaminated with food leftovers and non-recyclable materials. Hence, proper waste collection, transporting and sorting has to be done to recover larger amounts of PC plastics.

It is important to highlight that the different polymers in Figure 1 have different values when it comes to revaluation. Some polymers are far more recovered than others, rates for polyethylene terephthalate (PET) and high-density polyethylene (HDPE) commonly exceed 10%, while those for polystyrene (PS) and polypropylene (PP) are closer to zero [3]. Figure 2 shows some of the most used plastics currently.

Processing options are similar for both Post-Industrial (PI) and PC waste. When new raw materials are obtained via a mechanical processes, they typically lead to granulates, like the ones shown in Figure 3, and when the chemical approach is used, it typically leads to obtain monomer building blocks [4].

Mechanical processes of plastic recycling.

Mechanical recovery of plastic waste is the most common method for recycling, and the most developed market with well stablished supply chains. As explained by Plastics Europe [5], the process goes as listed and shown below:

  • Collection: Collection of end-of-life plastic products from separate and mixed waste streams
  • First sorting: Once plastic waste arrives at the recycling plant, it is sorted. While some sorting may have taken place at the collection stage, further separation by color or thickness may be necessary.
  • Shredding: Plastics need to be shredded into smaller pieces before they can go on for reuse.
  • Washing: Washing removes dust and dirt to ensure plastics are clean before they go onto the next stage. This can include removing traces of food, drink or labels.
  • Second sorting and control: Plastics are sorted again and controlled before being sent to extrusion.
  • Extrusion: Plastics flakes are finally converted into homogenous pellets ready to use in the manufacture of new products

As mentioned in the introduction, plastic waste comes from industrial and consumer origins, where PI waste tends to be better separated according to composition, so sorting is applied to PC waste much more often than to PI waste. The same goes for washing, as PC waste is usually more contaminated [4].

The most developed supply chains of mechanical recycling are those stablished for PET and PE (HDPE), this is because their polymer chain breaks down at a relatively low temperature, and so there is less degradation during the recycling process [7]. Nevertheless, in theory, all thermoplastics can be mechanically recycled with little or no impact on quality, the following list shows some of the most common examples of thermoplastics [5].

  • Acrylonitrile butadiene styrene (ABS)
  • Polycarbonate (PC)
  • Polyethylene (PE)
  • Polyethylene terephthalate (PET)
  • Polytetrafluoroethylene (PTFE)
  • Polyvinyl chloride (PVC)
  • Polymethyl methacrylate (PMMA)
  • Polypropylene (PP)
  • Polystyrene (PS)
  • Expanded Polystyrene (EPS)

Advantages and challenges

The major advantage of the mechanical recycling is that it is suitable for a decentralized implementation. Mechanical recycling plants are simple and inexpensive, have a relatively low demand on energy and resources compared with plants required for chemical recycling [8].

Mechanical recycling works the best with homogeneous streams of plastics. According to K. Ragaert et al. (2017), the use of coatings and paints complicate the process. Additionally, if contaminants are not completely soluble they can induce phase separation with a negative impact on the mechanical properties [4].

During mechanical recycling of polymers, two types of degradation are the most important:

  • Degradation caused by reprocessing (thermal-mechanical degradation)
  • Degradation during lifetime.

Both PI as PC plastics recycling suffer from degradation caused by a combination of heat and mechanical shear. Degradation occurring during lifetime by the long-time exposure to all sorts of factors in the environment (heat, oxygen, light, moisture, etc.). Nonetheless, this type of degradation is only important in the case of PC plastics recycling [4].

Chemical processes of plastic recycling.

Any reprocessing technology that affects either the formulation of the polymeric waste or the polymer itself and converts them into chemical substances and/or products, can be defined as chemical recycling (excluding energy recovery). Chemical recycling offers a viable option for plastic waste which is either more contaminated, or mixed and/or consist of multi-materials [9].

It is based on converting the polymers into smaller molecules. Chemical recycling routes can be roughly divided into thermochemical and catalytic conversion processes [4]. Some of the technologies one can find within this umbrella of chemical recycling are [9]:

  • Depolymerization: mostly focuses on monostreams independently sorted by plastic types, i.e., PET (including fibers), Polyamides or Nylon (PA), Polyurethane (PU), PMMA and Polylactic acid (PLA).
  • Pyrolysis and hydrothermal upgrading: mostly focus on mixed polymers, including multilayers, multi-materials within controlled limits (LDPE, HDPE, PP, PS).
  • Gasification: mostly focuses on mixed polymers.

Other classification of the process can be obtained when looking at the outputs of the technologies. Mechanical recycling does not change the structure of the polymers. Purification deals with the use of solvents for removing additives from the polymers, leaving the polymers almost unchanged. Depolymerization (Decomposition) breaks down the long hydrocarbon chains into shorter hydrocarbon fractions or into monomers using chemical, thermal or catalytic processes. At last, conversion technologies return plastic materials to the very basic components found in the input stream of the petrochemical industry [10]. A graphical summary is presented in Figure 3.

Advantages and challenges

In contrast to the mechanical recycling, the recyclate (the output of the recycling process) quality achieved at the end of the chemical recycling is comparable with the quality of virgin plastic materials [8].

From general perspective, the results of Life Cycle Analysis for chemical recycling processes are positive. Chemical recycling has a lower environmental impact in comparison with incineration during energy recovery; also lower than making plastics or specialty chemical products from fossil sources. However, it tends to have a higher environmental impact than mechanical recycling, although it varies between technologies and plastic streams treated [9].

A comparison table for advantages and disadvantages for both mechanical and chemical recycling is provided below.

Table 1 Advantages and disadvantages of chemical vs mechanical recycling. Adapted from [8].

PropertyMechanical RecyclingChemical Recycling
Technical requirements for infrastructure / processesLowHigh
Possibility of decentralized processingPossibleCurrently technically challenging and uneconomic
Requirement on quality for input streamHighLow-Medium
Quality of output materialDepends on the quality of input material. Moderate quality improvement using process parameters and additives is possible, but it is inversely proportional to the technical expenseVery High
Food regulatory approval of the outputIn special cases possibleHigh
Possibility of multiple recyclingLimitedPossible
Industrial maturityHighDepending on process, not fully mature
Environmental assessmentDue to the lack of data on the entire lifetime including multiple recycling, quality improvement steps and application-specific use of the recovered materials an accurate comparison is currently not possible. Although regarding ecological effect, mechanical recycling is expected to be more advantageous.

Case studies & Examples

In a pure mechanical recycling approach, ByFusion created the ByBlock. Using only steam (heat) and compression, the company zero-waste process repurposes unsorted mixed plastic waste into ByBlock without secondary additives or fillers. The ByBlock can be customized to specific densities, doesn’t crack or crumble like concrete blocks, requires no glue or adhesives, generates 83% less CO2 emissions than concrete blocks and can use construction residual material to create more ByBlocks.

In Italy, Ecoplasteam uses a patented process to treat polylaminates (plastic + metal layers) from PC waste streams to create a new secondary line of recyclable materials. By combining the use of mechanical recycling and some additives, Ecoplasteam ideated a new material produced from food packaging waste. When PC polylaminates are sourced from similar streams it results consistent over time in terms of composition and characteristics. This allows the new EcoAllene® material to be consistent and repeatable, allowing their clients to work with it the same as with raw material. Some images of the process and the applications of the new material are shown below.

Moving forward into chemical recycling, Makeen Energy company developed the Plastcon plant. This technology makes it possible to convert untreated and unsorted plastic waste into pyrolysis oil and other resources that can be used for the production of new plastic materials. The system accepts all types of plastic waste, no exceptions.

Depending on the specific setup and context, the system is able to produce about:

  • 75% pyrolysis oil, which can be used in the production of new plastic materials.
  • 15% gas which can be used to produce power or heat. The gas production consists of a mix of methane, ethane and propane.
  • 10% carbon black which can be used to color new plastic materials.



Chemical recycling and its CO2 reduction potential

Chemical recycling explained: an overview

What is Mechanical Recycling?

Graphical content:

Plastics: The Facts 2021


How does plastic recycling really work?

How to recycle the unrecyclable?

Other resources:

Precious Plastic Academy

The Circular Economy for Plastics – A European Overview


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[9]      “About Chemical Recycling | Chemical Recycling Europe,” ChemRecEurope. (accessed Feb. 17, 2023).

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