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Microbial Electrosynthesis of Bioalcohols through Reduction of High Concentrations of Volatile Fatty Acids

Gavilanes, José, Reddy, C. Nagendranatha, Min, Booki
Energy & fuels 2019 v.33 no.5 pp. 4264-4271
acetates, alcohols, bioenergy, butyrates, electrosynthesis, energy recovery, fuels, methane, methane production, pH, volatile fatty acids
The efficiency and characteristics of conversion of volatile fatty acids (VFAs) into alcohols by a microbial electrosynthesis (MES) process were significantly influenced by the initial organic loading concentration and operational period. The acetate and butyrate concentrations ranged from 2 to 8 g-COD/L, and alcohol and other product formations were determined over a 5 day operation. The highest yield of 0.218 g-CODAₗcₒₕₒₗ/g-CODVFAₛ was obtained for 4 g-COD/L after a 1 day operation. A gradual decrease over time in alcohol recovery was noticed for all VFA concentrations due to methane generation under elevated pH conditions. At the end of the operation, a higher bioalcohol yield was achieved at a relatively lower VFA concentration of 2 g-COD/L. A large fraction of initial VFAs remained unchanged without bioenergy production from higher substrate concentrations (6 and 8 g-COD/L). The energy recovery of total products (alcohols and methane) based on the input power was less than about 24% at the end of the operation. This study suggests that the optimized loading of VFA and low-pH conditions are essentially required to increase the overall performance of the MES system for alcohol production.