Hybrid PVC recycling via microwave pretreatment and microbial biopolymer conversion

Overview

This research addresses the long-standing challenge of recycling polyvinyl chloride (PVC), which is chemically stable and therefore recycled at much lower rates than other common polyolefins such as PET and PE. The proposed solution is a hybrid two-stage process: first, pressurised microwave energy is used to rapidly dehydrochlorinate PVC, and second, the resulting degraded material is fed to microorganisms that further break it down and convert it into useful biopolymers. The approach aims to turn a difficult waste stream into a feedstock for new bio-based materials, creating value while reducing landfill and incineration.

Technical specifications

Stage 1 – Microwave pretreatment:

• Uses a laboratory-grade microwave system delivering up to 1900 watts under high-pressure synthesis conditions, replacing domestic microwaves used in earlier trials.
• Achieves rapid dehydrochlorination of powdered PVC, reducing processing time from hours to minutes.
• Preliminary trials with chemical reagents such as sodium hydroxide, tetrahydrofuran with potassium hydroxide produced dark-brownish powders at 500 watts within 4 minutes.
• FTIR analysis confirmed carbonyl stretching at 1720 cm⁻¹ and short polyene chain formation at 1602 cm⁻¹, indicating successful dehydrochlorination.
• Planned characterisation includes FTIR, DSC, SEM, and HPLC to confirm degradation quality.
• Applicable beyond PVC to other polyolefins including PET, PE, and PP.

Stage 2 – Microbial conversion:

• Residual and partially degraded polymers from the microwave step serve as a carbon source for microbial degradation.
• Selection of specific bacterial strains enables production of targeted biopolymers such as polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB), and bacterial cellulose.

Technology readiness level

The concept has been validated at a preliminary bench scale, with initial microwave dehydrochlorination trials confirming the chemical changes expected from PVC breakdown. The current stage of work is moving from proof-of-concept toward laboratory optimisation, including scaling the microwave system to higher power and pressure, expanding feedstock scope to additional polyolefins, and demonstrating microbial conversion of the microwave-treated residues into biopolymers. Full validation of both stages is expected within a one-year research timeline. The technology is not yet commercially deployed and would benefit from industry partners interested in sustainable plastics recycling, biopolymer production, or circular-economy initiatives.