Waste volatile fatty acids as a good electron donor in microbial fuel cell with the iron-modified anode

The commercialization of microbial fuel cell technology is limited by high operating costs and low electricity production due to poor electron transfer to the anode. Operational costs can be lowered by utilizing waste materials, and cell performance can be improved by anode modification. This study investigated how anode modification with iron compounds changed the efficiency of energy generation and the microbiome of microbial fuel cells fueled with waste volatile fatty acids from a full-scale anaerobic digestion. Anode modification with 2.5 g Fe2O3/m(2) increased the power density, current density, and voltage by 3.6-fold, 1.8-fold, and 1.4-fold, respectively. In the microbial fuel cell influent, propionic, enanthic, and iso-caproic acids predominated (60, 15, and 13% of all volatile fatty acids, respectively); in the outflow, propionic (71%) and valeric acids (17%) predominated. In anodic biofilms, Acidovorax sp. were most abundant; they have a great capacity for volatile fatty acids decomposition, and their abundance doubled in the microbial fuel cell with an iron-modified anode. The presence of iron significantly increased the abundance of the genera Pseudomonas and Geothrix, which were mainly responsible for electricity production. These results indicate that anode modification with iron changes the anode microbiome, favoring efficient volatile fatty acids metabolism and a greater abundance of electrogens in the biofilm, which ensures better electricity generation.

Automated summary

The commercialization of microbial fuel cell technology is hindered by high operating costs and low electricity production due to poor electron transfer to the anode. This study explores the impact of anode modification with iron compounds on energy generation efficiency and microbiome in microbial fuel cells fueled with waste volatile fatty acids. Anode modification with 2.5 g of Fe2O3/m(2) increased power density, current density, and voltage. The presence of iron favored efficient volatile fatty acids metabolism and increased the abundance of electrogens in the biofilm, leading to improved electricity generation.