Volatile fatty acids production from bioplastics: Towards a circular bioplastics economy

Abstract

The feasibility of producing volatile fatty acids (VFAs) from five commercial bioplastics via acidogenic fermentation by a non-pretreated anaerobic sludge was investigated. Mesophilic batch acidogenic assays were set up for PHB, PHBV, PLA, PCL, PBS at 1.0, 10.0 and 20.0 g/L. The results obtained showed the feasibility of producing VFAs from PHB and PHBV, but not from PBS, PCL and PLA, rendering them non-biodegradable. However, only high substrate concentrations (10–20 g/L) resulted in organic overloading and decreasing the pH of the culture broth down to 4–5, which in turn induced the accumulation of VFAs via kinetic imbalance between acidogenesis and methanogenesis. Gaseous carbon (C-CO2 and C-CH4) accounted for 8–35% of the total initial carbon, while C-VFAs represented 10–18%, mainly as acetate and butyrate. This study represents the first systematically assessed proof-of-concept to produce VFAs from PHAs, which is key for the design of bioplastic-to-bioplastic recycling (bio)technologies.

Keywords: Biodegradation, Biorefinery, Microbial upcycling, Plastic waste, Polyhydroxyalkanoates, VFAs

JEL Classification: Q01