Power-generating trees: Direct bioelectricity production from plants with microbial fuel cells

Although plant-microbial fuel cells (PMFCs) have been considered as an alternative approach to utilize plants as an energy source, the application of a conventional PMFC coupled with rhizodeposits is immensely limited by environmental factors and plant species. In this research, we suggested a new concept for a device that can directly generate continuous bioelectricity from the plant stem associated with microbial fuel cells (MFCs), in which Pachira macrocarpa and Populus alba were employed. Compared with a conventional PMFC, the novel PMFC coupled with the plant stems produced more stable and continuous bioelectricity without oscillatory behaviour as well as a much shorter start-up period. The stem-coupled PMFCs produced bioelectricity that were operated at least 40 days. P. alba coupled PMFC showed higher power output compared to P. macrocarpa counterparts and the maximal power densities were 7.61 mW m(-2) and 3.60 mW m(-2) anode surface, respectively. Besides, we explored the response of the novel PMFC to different substrate concentrations and observed that the cell voltage effectively increased after the injection of moderate substrate concentrations. Moreover, the anodic bacteria formed a commensal relationship with the plant.