Effects of salinity, growing media, and photoperiod on bioelectricity production in plant microbial fuel cells with weeping alkaligrass

Abstract

This study investigated the potential for bioelectricity production of a salt-tolerant plant, the weeping alkaligrass (Puccinellia distans), in a plant microbial fuel cell (MFC). Air-cathode MFCs with a carbon felt anode were assembled in a cylindrical vessel. The MFCs were operated using growing media of different dry organic matter (OM) mass fractions: potting mix (OM: 89%) and sandy loam (OM: 8%), and treated with different NaCl concentrations of 0, 6, and 12 kg m−3. MFC performance was best at a salinity of 6 kg m−3. Over 114 days, the highest power output was obtained from plant MFC (PMFC) in potting mix at 83.7 mW m−2 cathode area with an average power of 12.78 mW m−2, followed by PMFC in sandy loam (maximum: 8.59 mW m−2, average: 8.35 mW m−2). The total biomass production of alkaligrass was 5–25% higher in the potting mix, when compared to the sandy loam. The presence of alkaligrass in PMFC increased the bioelectricity production by 14-fold compared to that of soil MFC (SMFC). In addition to the standard photoperiod of 16/8 h (light/dark), the MFCs were also operated under 24/0 h, 9/15 h, and 0/24 h photoperiods. Power outputs of 9/15 and 0/24 h were clearly decreased due to the effect of photoperiod, while the power outputs of 24/0 and 16/8 h were similar with some evidence of light-related inhibition. Frequent changes in the photoperiod test affected bioelectricity production and thus, a longer recovery time is recommended to reduce the adverse impact of the changes.