Chemical recycling of biofilms using ethanolysis enhanced by supercritical CO2
A green chemical recycling process for PLA and PHA biofilms that uses ethanol with supercritical CO2 to produce ethyl lactate and PHA monomers without harsh solvents or toxic catalysts. The approach enables closed-loop recovery of valuable chemicals from bio-based and mixed plastic waste streams.
Overview
This research develops a sustainable chemical recycling process for biofilms composed of PLA (polylactic acid) and PHA (polyhydroxyalkanoate) using ethanolysis enhanced by supercritical CO2. The process targets the recovery of ethyl lactate and PHA monomers, both of which are commercially valuable building blocks. By leveraging supercritical CO2 as a reaction medium, the approach avoids the need for harsh solvents and toxic or corrosive catalysts traditionally required for polymer transesterification reactions. The result is a cleaner, more energy-efficient pathway for recycling bio-based and mixed plastic waste.
Technical specifications
- Feedstocks: PLA and PHA biofilms, processed together or individually
- Reagent: Ethanol, selected because ethyl lactate is the most commercially valuable alkyl lactate
- Reaction enhancement: Supercritical CO2 lowers reaction temperature and eliminates catalyst recovery steps
- Catalyst option: TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene) or base catalysis considered only if needed to increase reaction rate
- Outputs: Ethyl lactate from PLA fraction; PHA monomers (such as 3-hydroxybutyrate from PHB) from PHA fraction
- Equipment: High-pressure, high-temperature reactor with planned addition of a CO2 high-pressure pump
- Characterization: NMR and complementary analytical methods for product identification and quantification
Technology readiness level
The project builds on published work demonstrating both catalysed and uncatalysed transesterification of PLA with alcohols. PHA-to-alcohol reactions are less established in the literature, with prior reports relying on toxic catalysts. Preliminary studies (approximately 6 months) will determine the temperature and pressure conditions for depolymerisation, define the role of supercritical CO2, and develop analytical methods. A subsequent 18-month phase will systematically identify and quantify the main operating variables affecting conversion, selectivity, and yield to establish optimum process conditions. Current readiness is early-stage (TRL 2-3), transitioning toward lab-scale validation.
About London South Bank University
London South Bank University is a large public, practice-led civic university with a strong professional and technical character, serving around 17,500 students within a wider education group. Its central London location places partners close to major employers, NHS organisations, public bodies and South London regeneration activity. LSBU works with around 2,000 employers through apprenticeships, workforce development, consultancy, Knowledge Transfer Partnerships and applied research, creating practical routes to engage expertise and develop talent. Research is supported by UKRI research councils, Innovate UK and the National Institute for Health and Care Research. Enterprise and knowledge-exchange services support collaboration, innovation and routes from research to market.
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