A mobile pilot plant has been designed to convert various types of plastic waste into oil. 

Developed by the Catalysis Engineering Group at the University of Amsterdam (UvA), the Solvothermal Liquefaction (STL) process uses a potent mix of solvent, heat, catalysts, and intense pressure to cook mixed plastic waste back into oil.

Interestingly, the resulting dark brown oil contains the precise molecules needed to remake brand-new, virgin plastic, thereby closing the recycling loop.

The pilot plant is heading to Spain to face its ultimate test: real municipal plastic waste. It offers a viable solution for keeping these materials out of landfills and incinerators.

“We have gained a deep insight into the process and are confident that it merits scaling up to industrially relevant volumes. That’s why we have now designed and manufactured a pilot reactor system as a first important step towards actual application,” said Associate Professor Dr Shiju Raveendran.

Cooks unsorted trash

The underlying technology is called Solvothermal Liquefaction. 

Rather than requiring workers or optical sensors to sort polyethylene from polypropylene, the STL process accepts the mixed plastic stream as is. The waste is fed into a 25-liter reactor vessel. Inside, it is blasted with solvent, subjected to high heat, and exposed to elevated pressure.

The key ingredient of all is the specialized nanostructured solid catalysts developed by the UvA team. These microscopic structures accelerate the chemical breakdown without being consumed by the reaction. In just 30 minutes, the molecular bonds of the plastics collapse.

The process cleanly splits the waste into three distinct products: gas, which is diverted to help power the system; char, which is filtered out as a solid byproduct; and a dark brown oil. This oil is packed with the pure monomers needed to manufacture brand-new, high-quality plastic.

Interestingly, the entire process closes the loop completely. The resulting plastic is identical to material made from fossil fuels, completely overcoming the degradation that usually happens during mechanical melting.

Circular plastic recycling

Academic breakthroughs die in labs every day because scaling them up is highly difficult. The team is attempting to beat those odds.

Backed by over €1.5 million from the larger €20 million European “PLASTICE” project, the technology has officially reached Technology Readiness Level (TRL) 6/7. In engineering, it means that the tech is ready for operational reality.

The Amsterdam researchers also partnered with an industrial engineering firm in India. Together, they designed and manufactured a heavy-duty, transportable system. The entire plant is complete with storage tanks, remote-control software, and rigorous safety overrides. It is mounted on automated steel frames called skids.

In Spain, the public waste management company COGERSA will host the pilot plant. For the first time, the machine will run on raw municipal waste streams rather than controlled laboratory feeds.

“Our lab experiments already included actual plastic waste, but we will certainly encounter challenges we could not fully foresee. That is precisely the purpose of this scale-up phase—to move the technology toward genuine industrial relevance,” said Raveendran.

If the skid-mounted reactor can withstand the chaotic composition of Spanish household waste this summer, it could pave the way for modular, decentralized recycling plants worldwide. 

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