Production of volatile fatty acids (VFAs) from five commercial bioplastics via acidogenic fermentation

The feasibility of producing volatile fatty acids (VFAs) from five commercial bioplastics via acidogenic fermentation by a non-pretreated anaerobic sludge was investigated. Mesophilic, anaerobic, acidogenic batch assays at 1, 10 and 20 g/L feed concentrations revealed the feasibility of producing VFAs from polyhydroxyalkanoates (PHA), i.e., PHB and PHBV, but not from PBS, PCL and PLA under the test conditions and time. However, only high PHA 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 PHA, which is key for the design of bioplastic-to-bioplastic recycling (bio)technologies.