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Pyrolysis – are we home dry?

Though a lot has been written about recycling and plastic waste processing options already, a truly comprehensive solution has yet to be found. And since the amount of waste isn’t getting any lower, and EU directives require up to 55% of plastic packaging to be made from recycled material by 2025, finding a truly effective way of recycling waste material, including plastic, is becoming imperative. 

Pyrolysis

The term recycling makes most of us think of mechanical processing- heating the material and pressing it into a new form. While this technology is often used, it has some shortcoming. For example, only certain types of plastic can actually be mechanically recycled. Furthermore, we mechanical recycling will never yield properties comparable with the raw material.      

“Currently, polyethylene or polyethylene terephthalate materials are best suited for mechanical recycling, but the products we obtain have a limited range of subsequent uses,” explains Jiří Hájek, General Director of Unipetrol Research Centre (UniCRE).

So though this technology does help us extend material lifecycle, the resulting product often does not meet the highest standards and can subsequently be used in a relatively small amount of applications.   

This is one of the reasons why great emphasis has been placed on developing thermal technologies for processing materials containing carbon, including plastics. A current favourite is pyrolysis technology. In pyrolysis, plastics, organic materials and materials containing carbon are broken down by heat in the absence of air. The resulting products are pyrolysis gas, liquid pyrolysis oil and a solid fraction – pyrolysis coke. This can be used, for example, to produce activate charcoal or carbon black. Pyrolysis fluids are a valuable commodity for the production of alternative fuels and chemicals. And since both solid fractions and pyrolysis gases contain highly concentrated feedstock energy, they can be used to power a pyrolysis unit in and of itself or to generate electricity.

“The best solution to the plastic waste problem is not to create any in the first place; the least optimal solution is landfilling. Pyrolysis or thermal decomposition of plastic waste is one option between these two poles,” explains Hájek.

Since plastics play an essential role in modern life and their significance will not diminish anytime soon, finding a reasonable balance between these extremes is indeed crucial. Many pyrolysis units are still in the testing phase, so we can’t declare an absolute victory over plastic waste just yet, but everything suggests that success is just around the corner.