Assessment of Chlorella vulgaris and Chaetoceros calcitrans as Algal Substrates in Microbial Fuel Cells

Microbial fuel cells (MFCs) offer a sustainable approach for simultaneous energy recovery and wastewater treatment. However, their performance is often limited by competition from methanogens in mixed-culture systems. In this study, dead biomass of Chaetoceros calcitrans was evaluated as an anodic substrate and compared with Chlorella vulgaris in dual-chamber MFCs. Anaerobic sludge was pretreated with algal biomass to assess methanogen inhibition and its influence on electrochemical performance. The MFC fed with Chaetoceros produced a higher maximum operating voltage (492 ± 2 mV) and average current (4.26 ± 0.2 mA) than the Chlorella -fed MFC (474 ± 3 mV and 3.84 ± 0.3 mA). Polarization analysis showed lower internal resistance in the Chaetoceros system (90 Ω) compared with the Chlorella system (200 Ω), indicating improved anodic activity. Although COD removal was slightly higher in the Chlorella -fed MFC (75 ± 7%) than in the Chaetoceros -fed MFC (71 ± 6%), coulombic efficiency was greater with Chaetoceros (19 vs. 16%), suggesting more effective electron recovery. Cyclic voltammetry, linear sweep voltammetry and Tafel analysis were consistent with greater electrochemical activity at the bioanode of the Chaetoceros -treated system. RT-qPCR analysis showed a substantially greater reduction in methanogen-specific gene abundance with Chaetoceros (68.75 ± 1.96%) than with Chlorella (10.23 ± 2.1%). Overall, Chaetoceros calcitrans appears to be a promising algal substrate for improving MFC performance and reducing methanogen abundance, as indicated by RT-PCR analysis; however, direct methane measurements are required to confirm methanogenesis inhibition.