Publication date: 21st July 2025
Volatile fatty acids (VFAs) are valuable platform chemicals and can be obtained, among others, during the anaerobic dark fermentative (DF) treatment of organic waste, such as kitchen waste (KW). To improve the performance of DF, in this work potentiostatically controlled cathodic electrofermentation (EF) was studied and compared with conventional fermentation (CF) to produce VFAs based on vegetable-based KW in batch operation. Two initial organic loads (OLs) were applied based on the volatile solids (VS) in KW, namely 30 and 45 gVS/L. The modified Gompertz model was used to evaluate total VFA and butyric acid formation during the fermentations (lasting 9–10 d). Compared to CF, the EF operation significantly enhanced the kinetics of VFA formation by reducing lag-phase length (by 60–80 %) and promoting chain elongation, particularly at high OL. Final VFA yields (up to 1.2 gVFA/gVS and 0.5 gVFA/gVS for OL = 30 gVS/L and 45 gVS/L, respectively) were similar for EF and CF, yet EF led to a more consistent fermentation process and even improved caproic acid yield. Metagenomic analysis confirmed the presence of key chain-elongating genera (Clostridium, Caproicibacterium, Caproiciproducens) in each experimental setup, while EF did not induce notable shift in microbial consortia profile compared to CF. The enhanced performance with EF could be attributed to the potentially more efficient redox balancing and cofactor regeneration as a result of the electrochemical stimulation. This study highlights EF as a promising technique to improve and steer VFA production from complex biowaste in DF.
T.R. was supported by the János Bolyai Research Scholarship of the Hungarian
Academy of Sciences. The support of the 2024-2.1.1-EKÖP University Research
Fellowship Program of the Ministry of Culture and Innovation from the source of the
National Research Development and Innovation Fund is duly acknowledged (L.K.).
The Authors acknowledge the project no. RRF-2.3.1-21-2022-00009, titled National
Laboratory for Renewable Energy has been implemented with the support provided by
the Recovery and Resilience Facility of the European Union within
the framework of Programme Széchenyi Plan Plus.
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