Azolla enhances electricity generation of paddy microbial fuel cell

Generation of electricity from plant rhizodeposition with an aid of soil bacteria has gained popularity recently as a source of clean and green energy. Power generation from such biosystems is lower than theoretically achieved value due to many constraints. Supplementing the rhizodeposition with external substrates or in situ complementary mechanism can help to enhance the current generation. Therefore, this study aims to improve current from paddy plants with an amendment of Azolla which is hypothesized to augment the bioelectricity production via two mechanisms. These include an addition of organic matters in the system and nitrogen fixation from Azolla which plays a positive role in biomass growth, thereby increasing current. Single chamber sediment PMFCs were built in a facile way, employing commercially available glass chambers with carbon cloth for electrodes, and paddy soil as substrates and inoculum. To have better insight about the system performance, numerous parameters were monitored including daily power output recordings, nature of electric signals, polarization technique, growth nature of the plant, and change in soil physiochemical characteristics. The results revealed that after a week of transplanting of paddy seedlings, the daily current density increased almost twice as compared to the unplanted system. The maximum power in planted reactors was greater by 84% as depicted by power curve. In addition, amended planted reactors with Azolla enhanced the current generation by almost thrice than only planted reactors without amendment, while planted reactors produced current twice than that of from sediments only. Clear circadian oscillation was observed in power output from closed circuit while there is no such demarcation in open circuit voltage during the start-up period.