Polyaniline-modified anodes for brewery waste treatment in microbial fuel cells: insights into inoculum selection, cell configuration, and lactic acid valorization

Abstract

BACKGROUND

This study focuses on the treatment of brewery waste slurries (BWS) with high chemical oxygen demand (COD) using a single-chamber microbial fuel cell (MFC) inoculated with heat-treated anaerobic seed sludge. A co-substrate of 5 g L⁻¹ glycerol was added, and carbon felt (CF) was employed as the anode material, enhanced through in situ polymerization of aniline (PANI/CF). Additionally, the adsorption of ruthenium dioxide nanoparticles onto the modified CF was assessed (PANI-RO/CF).

RESULTS

Tests conducted at room temperature (19 °C to 22 °C) achieved an average COD reduction of 36%. The PANI-RO/CF electrode accumulated 24% more charge, resulting in the highest coulombic efficiency of 75.1%, significantly exceeding similar studies. However, the PANI-modified anode generated more energy, exceeding that of the bare CF by more than double, reaching 57.1 mW m⁻². An optimized working volume was identified in relation to other reported works. Microbial population analysis revealed an interaction between Staphylococcus epidermidis and a rarely reported psychrophilic Bacillus species. After 30 h, lactic acid emerged as the main by-product, with a concentration of 7.5 ± 0.6 g L⁻¹.

CONCLUSIONS

These findings highlight an optimization approach based on cell configuration and inoculum selection, as well as a significant valorization pathway that is frequently overlooked in the existing literature on brewery wastewater treatment using MFCs, particularly regarding the attractiveness of lactic acid production. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).