How is plastic recycled?

There are two ways that plastic is recycled, mechanical and chemical recycling. In this blog we will discuss them both and the key advantage and disadvantage of each.

Mechanical recycling

This is the most common method of recycling plastics. Firstly, plastic waste is sorted based on the type and quality. Next the plastics are cleaned to remove contaminants, this step is crucial to maintain the quality of the recycled material. The cleaned plastics are then mechanically shredded or granulated into smaller pieces. The shredded plastic is then melted and forced through an extruder to create pellets or other forms of raw material. These pellets can be used as feedstock for manufacturing new plastic products.

The key advantage of mechanical recycling is that it is much more energy efficient than the energy-intensive processes required in chemical recycling. This energy efficiency means there is lower carbon emissions and reduced operating costs.

The key disadvantage of mechanical recycling is that it is limited in its ability to process a wide range of plastic types effectively. Plastics must be similar and free from contamination to achieve high-quality recycled materials. This limitation restricts the types of plastics that can be recycled using mechanical methods and means a significant portion of plastic waste cannot be recycled using mechanical recycling.

Chemical Recycling

Chemical recycling involves breaking down used plastics into their chemical constituents or converting them into new chemical compounds. It is a much more complicated process that mechanical recycling. The first step is depolymerisation, this is where the long polymer chains which make up plastic are broken down into smaller segments. This is done by heating up the plastic without oxygen (pyrolysis), turning it into gas (gasification) or by using special liquids (solvolysis). The depolymerised plastic is then transformed into feedstock which can be used to create new plastics.

The key advantage of chemical recycling is that it is more versatile when it comes to processing contaminated or mixed plastics. This is unlike mechanical recycling which requires meticulous sorting and cleaning. This advantage makes chemical recycling suitable for handling a wider range of plastic waste streams, reducing the need for stringent pre-processing steps.

The key disadvantage of chemical recycling is that chemical recycling processes can be energy intensive. Methods like pyrolysis or gasification require high temperatures and energy inputs to break down plastics into their chemical constituents. This energy intensity can lead to higher operating costs and negate some of the environmental benefits if the energy source used is not renewable or low carbon.