How Is Plastic Recycled? Process, Types, and Sustainability

Published at 12 November 2025

Plastic has transformed modern life, but it has also become one of the greatest environmental challenges of our time. At SINTAC, we have spent more than three decades leading plastic recycling in Spain, promoting the circular economy and helping companies and institutions turn their waste into valuable resources.

More than 400 million tonnes of plastic are produced every year worldwide, yet only a small share is recycled properly. Our objective is to reverse this trend through technology, expertise and long-term commitment.

Below, we explain how plastic is recycled, the main processes involved, the types of plastics that exist and how they can be transformed into sustainable new products.

Why Is Plastic Recycling Important?

Since 1950, more than 8 billion tonnes of plastics have been produced (Geyer et al., Science Advances, 2017). Around 80% of this has ended up in landfills or the environment, while approximately 8 million tonnes enter the oceans each year (Jambeck et al., Science, 2015).

The issue is not only environmental but also economic. Every non-recycled package represents a loss of reusable raw material and a missed opportunity to reduce costs and emissions. Recycling plastic is therefore a strategic necessity for governments, companies and consumers.

At SINTAC, we work under the premise that every polymer can have a second useful life, becoming new industrial or consumer products and closing the loop within a real circular economy.

Types of Plastics and Their Recyclability

To understand the recycling process, it is essential to know the main types of plastics and their identification codes. Not all plastics are the same nor can they be recycled in the same way. At SINTAC, we use advanced optical sorting, magnetic separation and chemical processing technologies, allowing us to optimise the recovery of each type of polymer.

Stages of the Plastic Recycling Process

Plastic recycling involves several technical phases designed to ensure purity, traceability and quality of the final material. Although there are different recycling methods (mainly mechanical and chemical recycling), all begin with proper separate collection at source.

1. Reception of Raw Materials

Incoming materials are inspected to assess quality, characteristics and composition. Non-recyclable elements are removed, and materials are sorted into three main categories:

Metals
Film plastics and mixed plastics
Rigid plastics (PET, HDPE, PP)

A correct initial classification is essential to ensure efficiency and quality in later stages.

2. Advanced Sorting and Separation

Materials are separated by polymer type, colour and density using automated systems such as NIR optical sorters, eddy current separators and flotation tanks.

3. Shredding

Plastics are reduced into flakes to facilitate washing, drying and homogenisation.

4. Washing and Centrifuging

The material is cleaned to remove impurities, inks and organic residues, and then centrifuged to eliminate excess moisture.

5. Drying

A controlled drying process preserves the physical and mechanical properties of the plastic.

6. Homogenisation and Compaction

The material is mixed and compacted to ensure uniform texture, colour and density.

7. Storage and Preparation for Transformation

The cleaned and stabilised material is stored for mechanical recycling (melting and pelletising) or chemical recycling (breaking polymers down into monomers).

Thanks to this complete process, plastic waste becomes high-quality secondary raw material, ready to re-enter the production cycle.

Mechanical vs. Chemical Recycling

Mechanical Recycling – the Most Common Method

This process, applied mainly to thermoplastics, uses physical transformations – such as extrusion, filtering and pelletising – to produce new recycled pellets. It is efficient and widely used in industrial manufacturing.

Chemical Recycling – Innovation for the Future

Chemical recycling breaks plastics down into their molecular components using heat or catalysts. Techniques include pyrolysis, gasification and depolymerisation. This method allows the recovery of complex or contaminated plastics that cannot be treated mechanically.