Every year, the world generates hundreds of millions of tonnes of plastic waste, and the vast majority of it ends up in places where it is not useful. A landmark 2025 study published in Nature Communications Earth & Environment, which conducted a global trade-linked material flow analysis of plastics for 2022, found that the global plastic recycling rate has remained stuck at just 9 per cent, with incineration now the dominant disposal method at 34 per cent and landfilling at 40 per cent. Against this backdrop, a team of researchers at the University of Amsterdam has built something that could change the math entirely: a mobile, 25-litre pilot reactor that takes mixed, unsorted plastic waste and converts it into reusable oil in under 30 minutes. It is heading to Spain this summer for its first real-world test, and the results could reshape how the world handles one of its most persistent pollution problems.
What is solvothermal liquefaction and how does the UvA plastic waste recycling process work
The technology at the heart of the pilot plant is called Solvothermal Liquefaction, or STL. Developed by the Catalysis Engineering Group at the University of Amsterdam’s Van ‘t Hoff Institute for Molecular Sciences under Associate Professor Dr Shiju Raveendran, it works by feeding mixed plastic waste directly into a sealed reactor vessel, where it is subjected to a combination of solvent, elevated heat, and high pressure. The critical innovation is a set of specially engineered nanostructured solid catalysts developed by the UvA team. These microscopic structures accelerate the chemical breakdown of the plastic’s molecular bonds without being consumed by the reaction itself, meaning they can be reused across cycles. Within 30 minutes, the process splits the plastic feedstock cleanly into three outputs: gas, which is redirected to help power the system itself; char, a solid byproduct that is filtered out; and a dark brown oil.A 2022 study in the Chemical Engineering Journal on solvothermal liquefaction of polyethene-based plastics found that the oil produced by the STL method had a higher heating value comparable to that of gasoline, confirming the energy quality of the output. Crucially, the oil also contains the monomers, the base molecular building blocks needed to manufacture brand-new, virgin-quality plastic, not degraded secondary material.
Why sorting-free chemical recycling of mixed plastic is a game-changer for the circular economy
The single biggest bottleneck in plastic recycling globally is sorting. Conventional mechanical recycling requires waste to be separated by plastic type, polyethene from polypropylene, PET from PVC, before it can be processed. In practice, most municipal plastic waste is a mixed, contaminated stream that makes this segregation expensive, labour-intensive, and often economically unviable. The result is that huge volumes of technically recyclable material end up incinerated or landfilled anyway.STL sidesteps this entirely. The reactor accepts the mixed plastic stream as-is, regardless of composition. According to the UvA’s Van ‘t Hoff Institute for Molecular Sciences, a key feature of the process is that it can handle all types of plastics simultaneously making it directly suited to the complex, contaminated waste streams that existing infrastructure cannot handle. The process has been validated through kinetic studies, Computational Fluid Dynamics modelling, and techno-economic analyses, all of which supported its development from bench scale to the current pilot stage.
The PLASTICE project: Europe’s €20 million push toward closing the plastics recycling loop
The STL technology was developed within the broader European PLASTICE project, a €20 million EU-funded research initiative focused on closing the plastics recycling loop through novel conversion routes. Of that total, over €1.5 million was allocated specifically to Raveendran’s Catalysis Engineering Group at UvA to develop and demonstrate the STL process.The project has brought the technology to Technology Readiness Level (TRL) 6/7 a significant milestone in engineering that indicates readiness for an operational environment rather than a controlled laboratory. To build the actual pilot plant, the Amsterdam team partnered with an industrial engineering firm in India, together designing and manufacturing a heavy-duty, transportable system complete with storage tanks, remote-control software, and rigorous safety overrides. The entire installation is mounted on automated steel frames known as skids, making it modular and relocatable, an important design choice for a technology that could eventually be deployed at decentralised waste processing sites around the world.
Spain’s COGERSA waste facility: Testing the pilot reactor on real municipal plastic waste
The pilot plant’s first operational test will take place at COGERSA, a public waste management company in Spain. This is where the technology faces its most demanding challenge yet not controlled laboratory feeds of pre-selected plastics, but actual municipal waste streams with all the variability, contamination, and compositional complexity that real-world waste brings.A 2025 study by UvA researchers, published in the Chemical Engineering Journal, examined the use of hydrothermal liquefaction on real post-consumer high-density polyethene-rich municipal waste in collaboration with COGERSA and TotalEnergies, establishing the scientific groundwork for this exact operational context. That study found the process capable of converting real-world municipal plastic waste into new plastic monomers, validating the feedstock assumptions the summer trials will now put to a larger-scale test.”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,” Raveendran said.
What happens to the oil produced and how STL could scale into industrial chemical recycling
The oil output from the STL process is not a fuel end-product it is a feedstock. The dark brown oil produced after each 30-minute cycle contains the precise molecules required to manufacture new, virgin-quality plastic that is chemically identical to plastic made from fossil fuels. This closes what researchers call the circular plastic loop: waste plastic goes in, and the raw material for new plastic comes out, without the quality degradation that typically happens during conventional mechanical melting and remoulding.If the Spanish trials demonstrate consistent performance on real municipal waste, the modular skid-mounted design of the pilot plant means it could be replicated and deployed at waste processing facilities globally without requiring large, centralised infrastructure. The technology’s viability at TRL 6/7 also means the path to commercial-scale industrial deployment is shorter than for most early-stage recycling innovations, a distinction that matters in a sector where many breakthrough processes have historically stalled between the laboratory and the factory floor. Go to Source
