Enhanced carbon capture and medium chain fatty acid production using microbial electrosynthesis: Role of electrode...

Balancing the surface area of electrodes to reactor volume (SA/V) ratio in microbial electrosynthesis (MES) systems is crucial for enhancing electron transfer, biofilm development, and product yield. Batch MES experiments were conducted using cathodes with SA/V ratios of 40 cm² L^-1 (MES-1), 150 cm² L^-1 (MES-2), 260 cm² L^-1 (MES-3) and 333 cm² L^-1 (MES-4), selected based on statistical analysis of previous studies. Among these, MES-3 (260 cm² L^-1) demonstrated the highest caproic acid production of 1.5 ± 0.2 g L^-1 and selectivity 67 %, outperforming MES-1, MES-2, and MES-4 by 2.1, 1.4, and 4.4 times, respectively. MES-3 had improved mass and electron transfer while maintaining effective microbe-electrode interactions. Additionally, MES-3 showed the lowest energy consumption (6.5 ± 2.3 kWh mol^-1 VFAs) and a higher electron recovery efficiency (55.8 ± 18.3 % at 2.5 V). These results demonstrate that balancing SA/V ratio is key to enhancing MES performance and sustainable MCFA production.