Harnessing plant microbial fuel cells for resource recovery and methane emission reduction in paddy cultivation

[Display omitted] •Plant-MFC conceptualised for onsite recovery of nutrients from paddy cultivation.•The cathode chamber of the plant-MFC yielded a total of 1.27 L of catholyte.•An additional floating cathode enhanced the sustainability of the plant-MFC system.•Biochar served dual-purpose, acting as soil amendment and part of plant-MFC anode.•Biochar amendment & MFC integration reduced paddy microcosms' methane-flux up to 57 %. The primary objective of this study is to improve the eco-sustainability of the flooded rice-based system by integrating a tubular configuration of a plant microbial fuel cell (plant-MFC) with a terracotta membrane. The emphasis was placed on enhancing resource recovery and mitigating greenhouse gas emissions from rice cultivation. The study utilizes the 'Improved White Ponni' variety of medium duration Paddy (Oryza sativa L.) as the model plant. Additionally, biochar derived from Typha angustifolia L. was incorporated in the paddy growing matrix as a dual-purpose element, serving both as a soil amendment and as an integral part of the plant-MFC anode. The plant-MFCs with additional floating cathodes coupled with biochar amended paddy microcosm (PMFC-BC) exhibited the highest power density (46.8 mW/m2) with reduced methane emissions compared to the other types of plant-MFCs studied. A total of 1.27 L of catholyte was collected from PMFC-BC for the 15-week study period. The energy-dispersive X-ray analysis of the catholyte sediments showed the presence of various elements including N, Na, C, Mg, K, Cl, P, Ca, Si, Fe, O, Ti, etc., indicating the migration of soil nutrients across the terracotta membrane and chemical precipitation in the cathode chamber of plant-MFC. In the active tillering phase of the paddy, the methane emission flux from PMFC-BC was 57 % less when compared to the paddy microcosm without any MFC integration. It is believed that the integration of this type of plant-MFCs which can generate direct electricity, recover catholyte with nutrients, and reduce methane emissions from the paddy growing matrix will make rice cultivation truly sustainable and carbon negative.