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Waste-to-energy vs. pyrolysis: competing agendas for sustainable development
Thermoplastics are the only material which can be mechanically recycled. Furthermore, the material must be clean and made up of only one polymer type. Since only a fraction of plastic waste meets these relatively strict requirements, today we only recycle around 30% of sorted plastic. The rest gets sent to landfills or for energy utilization, either in municipal waste incinerators or as a solid alternative fuel (SAF) in cement factories.
Pyrolysis appears to be one of the promising additions to current recycling technologies. Can pyrolysis be a better, greener process than energy utilization?
How does pyrolysis compare with conventional energy utilization when it comes to emissions?
A study by Sphera Solutions GmbH titled “Evaluation of pyrolysis with LCA - three case studies" shows that pyrolysis produces 1162 kg CO2-eq when processing 1000 kg of waste plastics. The contribution analysis shows that 66% of this impact comes directly from the pyrolysis oil process, 9% from the pyrolysis oil purification process and 26% of the impact is associated with sorting, waste collection, post-sorting and transportation.
Tested incineration technologies MSWI (Municipal Solid Waste Incineration) and RDF (Refuse Derived Fuel incineration technology) produced emissions around 2990 kg CO2-eq, i.e. almost three times more. The contribution analysis shows that 93% of that impact comes from the incineration process and only 7% is associated with the waste collection, sorting, post-sorting and transportation.
Pyrolysis- a friend to circular economy
The process of pyrolysis, one of the available methods of chemical recycling, can return dirty, at first glance degraded mixed plastic waste back into circulation. Energy utilization provides us with the energy inside the material, but nothing more. In addition, its incineration releases a significant amount of CO2 emissions into the atmosphere. Pyrolysis products, on the other hand, enable the creation of new plastic materials of the same quality as products from primary sources
And the winner is…
Energy processing in incinerators utilizes the high calorific value of plastics and returns it to circulation in the form of thermal energy.
The pyrolysis process returns prime quality materials into circulation and produces only about a third of the emissions in with incineration technologies.
Energy processing has and always will have a role to play, but a future that strives to fulfill the goals of a circular economy and conserve natural resources will always prioritize recycling processes such as pyrolysis.