Influence of iron fertilizer form and concentration on bioelectricity and methane emission from hydroponic plant microbial fuel cells

This study aimed to evaluate the effect of iron form (Fe2+ and Fe3+) and concentration (0 mu M, 7.5 mu M, and 15 mu M) on the biomass production, bioelectricity generation, and methane (CH4) emissions of hydroponic plant microbial fuel cells (H-PMFCs). Rice plants (Oryza sativa L.) were grown in H-PMFCs. During the 90 days of operation, the highest power density (PDmax) was observed in Group 7.5-15 of 949.17 mW/m(3). When adding single-form iron (Fe2+ or Fe3+), the PDmax of H-PMFCs was positively correlated with iron concentration. Further, the H-PMFC feed with Fe3+ showed higher power output than the feed with Fe2+. Adding 7.5 mu M Fe2+ and 15 mu M Fe3+ (Group 7.5-15) showed the highest overall biomass production, including plant lengthavg/plant (89.67 +/- 1.17 cm) and plant weightavg/plant (14.91 +/- 0.02 g dry mass) and lowest CH4 emission (43.15 +/- 2.00 g/ m(2)). The CH4 emission test indicated that the addition of iron in rice H-PMFCs can decrease the emission of CH4 in two ways: (i) iron electron acceptors directly inhibit methanogens; (ii) iron electron acceptor enhances the electricity production ability of MFC to inhibit CH4 production. Therefore, adding 7.5 mu M Fe2+ and 15 mu M Fe3+ showed great potential to enhance the performance of H-PMFCs on biomass production, bioelectricity generation, and CH4 emission inhibition.

Automated summary

This study evaluated the effect of different forms and concentrations of iron on hydroponic plant microbial fuel cells. The results showed that adding 7.5μM Fe2+ and 15μM Fe3+ significantly improved biomass production, bioelectricity generation, and reduced CH4 emissions.