Difficulties with Recycling Plastic

Background

Plastic is made by joining monomers, which come from oil and gas, into polymer chains. The chemical bonds in the chains are strong, and it takes a lot of energy to break them, which is why plastic does not break down easily.

Mechanical Recycling

Commonly called ‘Recycling’ - plastic is reprocessed into a new material without changing its chemical structure, (i.e. without breaking the polymer chains).

Associated Problems

Odour, taint, colour, contamination, loss of quality, and suitability for food contact, are all problems associated with mechanically recycled plastic. Only certain polymers can be mechanically recycled.

State of Technology

Chemical or thermal recycling refers to using heat to break the bonds in the polymer chains to return them back to their original building blocks. In other words, turning waste plastic back into oil and gas. This oil and gas can be used in the production of new plastics which are indistinguishable in quality to virgin plastics.

 

Chemical recycling as a process is still in its infancy, mainly due to:

(i) problems associated with transferring heat into large volumes of plastic;

(ii) the quality of the end products of the process;

and the need to separate out plastics containing corrosive additives such as chlorine.

The PVC Space

PVC is an extremely versatile polymer, valued because it can be used in a diverse range of applications, including rigids and flexibles, and can be formed into products requiring complex shapes.  In packaging, it can be found in various forms, such as meat trays, plastic film, laminates and blister packs.

.

Recycling PVC

PVC is seen as problematic for recyclers as it is not easily recyclable alongside other polymers, and it also contaminates plastic - such as PET or HDPE - which could otherwise be recycled.

Both energy from waste providers, and existing chemical recycling* technologies, avoid processing chlorine-contacting plastics (which make up 20% of plastic manufactured) because one of the products of chemical breakdown of chlorinated plastic is hydrochloric acid.  Hydrochloric acid causes damage to the metallic equipment required to cope with the high temperature environment needed in traditional chemical or ‘thermal’ recycling..