Supercritical water approach to plastic recycling

The University of Birmingham has licensed the rights to a ‘supercritical water’ technology to Stopford, to develop a novel process for recycling mixed plastic packaging, that delivers a greater proportion of high value recycled plastic with less emissions, fewer processing steps than current recycling methods, and no solvent residues. The approach was invented by Dr Bushra Al-Duri, from the University’s School of Chemical Engineering and further developed during a collaborative project with Stopford.

Above the critical point of 374.5 ^oC and 220 bars (217 atmospheres), water is described as ‘supercritical’ where its properties and operational behaviour are completely different from ambient/hot water. Supercritical water can be a solvent for all organic materials including plastics. Its gas-like penetration power makes it a superior medium to decompose mixtures of complex waste plastics into value-axdded materials, which are feedstock for manufacturing new plastics.

Stopford will now use its substantial technology innovation and engineering expertise to further develop and scale the novel hydro-thermal process called CircuPlast, enabling the conversion of non-recyclable end of life plastics into high-value chemicals for use as feedstock for the plastics industry. 

Stopford’s Technology & Innovation Director Dr Ben Herbert said that the agreement enables Stopford to fast-track the development of the CircuPlast technology to meet the plastics management and sustainability requirements of multiple industry sectors. David Coleman, CEO of University Birmingham Enterprise, said that the growth of plastics production has long outstripped the capacity for recycling, with the UK alone producing over 2 million tonnes of plastic packaging waste each year, of which just over half is recycled.  The collaboration delivers a viable way of recycling much more plastic packaging that will help meet sustainability goals.

CircuPlast will be an eco-friendly technology using ‘supercritical’ water rather than industrial solvents for the repurposing of waste plastics adopting a circular approach. The technology will provide a sustainable alternative to fossil oil derived feedstocks with no CO2, emissions in the production or disposal phases.

Dr Al-Duri further said supercritical water technology represents the next generation for treatment and recycling of ‘stubborn’, complex, and hazardous waste that is currently treated by incineration or sent to landfill.   CircuPlast is expected to overcome the substantial limitations of existing recycling processes by enhancing recycling rates, enabling an increase in the recycled content of plastics, maintaining functionality, to a level that is currently unachievable using mechanically recovered materials.