Decarbonisation Technology May 2025 Issue

Waste plastic preparation 1

Heat

Depressurisation Product

Optional processing and storage

Hydro-PRT conversion unit

Heat and pressurisation

Mix with supercritical water

separation

Figure 1 The Hydro-PRT process flow diagram showing the end-to-end hydrothermal advanced plastic recycling process

mind that the hydrothermal liquefaction (HTL), process, trademarked as Hydro-PRT, was developed by Mura Technology. Introducing Hydro-PRT In brief, Hydro-PRT is an end-to-end hydrothermal advanced plastic recycling process that uses supercritical water to crack post-consumer, multi-layer flexible and rigid mixed plastic waste streams into industry- ready, circular hydrocarbons. Mura develops its own build-own-and-operate Hydro-PRT recycling facilities and sells licences for use of the technology through Mura’s exclusive Global Licensing Partner, preferred engineering partner, and investor, KBR. KBR has already agreed licences for the Hydro-PRT technology with organisations including LG Chem and Mitsubishi Chemical. This next-generation process is unique when compared with other advanced recycling technologies. It is differentiated by its use of supercritical water, which is water brought to a state of increased temperature and pressure until it exceeds its critical point, where it exhibits both the properties of liquids and gases. Using supercritical water in this way brings numerous benefits when treating plastic waste streams, ultimately making possible the processing of those waste streams usually considered unrecyclable by other existing recycling technologies. Hydro-PRT is insensitive to organic contaminants such as paper labels and cardboard or organic matter like food residue, making it an ideal solution for the contaminated plastic waste streams that typically get incinerated within the

UK and Europe. A 2024 study estimated that as much as 46% of UK household plastic waste is incinerated ( Greenpeace UK, 2024 ). By providing an alternative destination to energy-from-waste facilities for plastic waste, the greenhouse gas emissions resulting from incineration are consequently avoided. Unlike pyrolysis, an alternative form of advanced recycling, the use of supercritical water during conversion allows for highly efficient and homogeneous heat transfer, as it surrounds the plastic waste rather than heating from an external source. The use of supercritical water also offers a source of hydrogen, which can saturate the broken chemical chains in the recycling polymers, with the hydrogen transferring from the water into the end products. The presence of supercritical water in the reaction also limits the formation of char, meaning the quality of the final output product is not affected. These homogenous reaction conditions, in turn, allow the cracking rate to be controlled during operation, acting as a suppressant to unwanted free radical reactions. This ultimately makes very high yields of high-quality circular hydrocarbon products possible and gives them increased stability. Practically, the process begins with the transportation of post-consumer plastic waste, which could not otherwise be processed via traditional mechanical recycling, to a Hydro- PRT facility. The waste is shredded, and any contaminants such as stones, glass, metal, and non-target plastics are removed. Once sorted, the plastic is moved into an extruder where it is melted and pressurised before being injected into the main conversion unit where the Hydro-