Pyrolysis

Pyrolysis is a thermal technology that decomposes organic waste, plastics or tyres in the absence (or near absence) of oxygen, transforming them into valuable products such as oils, gases and solid carbon (char). Together with gasification, it offers an alternative to simple incineration or landfilling. As the circular economy expands, pyrolysis is increasingly seen as a tool for closing material and energy loops.

Operating range

The reaction typically takes place between about 350 and 700 °C, depending on the feedstock. Lower temperatures favour oil production, while higher temperatures favour gas formation.

Equipment and systems

• Rotary kiln: well suited to plastics and tyres.
• Fluidised bed: good for biomass.
• Vacuum pyrolysis: maximises oil purity.

Modern units include automated control of temperature and residence time.

Suitable materials

• Non-recyclable plastics (PE, PP, PS).
• Agricultural and forestry biomass.
• Sewage sludge.
• End-of-life tyres.

As an indicative figure, around 0.6 to 0.8 kg of pyrolysis oil can be obtained per kilogram of plastic waste, usable as a partial substitute for diesel, although yields vary widely with feedstock and process conditions.

Industrial applications

• Production of alternative fuel.
• Generation of steam and electricity.
• Recovery of base hydrocarbons for green chemistry.
• Production of biochar as a soil amendment.

Environmental benefits

• Reduces the volume and hazardousness of waste.
• Recovers energy from materials with no recycling value.
• Can lower CO2 emissions compared with direct incineration.
• Recovers carbon contained in biomass.

Technical and economic challenges

• Controlling chlorine or sulphur content in plastic waste.
• The need for gas and oil cleaning systems.
• High upfront investment.
• The absence of stable regulatory frameworks in some countries.

Spanish and European framework

Law 7/2022 and regional waste plans recognise energy recovery routes within the circular-economy model. At EU level, the Waste Framework Directive, as amended by Directive (EU) 2018/851, frames how recovery and chemical recycling outputs may be counted, with the detailed accounting rules still developing.

Innovations and trends

• Catalytic pyrolysis: using catalysts to improve yield and selectivity.
• Co-pyrolysis of biomass and plastics to improve oil quality.
• Integration with hydrogenation to produce higher-quality biofuels.

At Manglai we help companies compare waste-treatment routes and measure their carbon footprint. Discover how Manglai can help you.