Microbial fuel cells, macropore, and farm-oriented enhancing aquatic systems: Evaluating their impact on redox potential and greenhouse gas emissions in paddy soils.

Rice paddies are significant sources of methane (CH₄) and nitrous oxide (N₂O) emissions due to anaerobic conditions that promote methanogenesis and denitrification. Maintaining redox potential is a key strategy for mitigating these emissions. This study evaluates the effectiveness of Microbial Fuel Cells (MFCs), Macropore (MP), and Farm-Oriented Enhancing Aquatic Systems (FOEAS) in regulating redox potential and reducing greenhouse gas (GHG) emissions in paddy soils. Results show that MFC increased redox potential by 40.92 %, reducing N₂O emissions by 10.8 % (4.172 g ha^-1 d^-1 vs. 4.679 g ha^-1 d^-1 in the control) but elevated CH₄ emissions 2.5 times (10.235 kg ha^-1 d^-1 vs. 4.181 kg ha^-1 d^-1 in the control). MP exhibited the lowest CH₄ emissions (2.579 kg ha^-1 d^-1) and reduced N₂O emissions by 5 %. FOEAS moderately reduced CH₄ emissions but had minimal impact on N₂O flux despite the increase in redox potential in the deeper layer. These results highlight trade-offs in electron-accepting technologies for GHG mitigation. Since redox control occurs locally in all methods, optimizing electrode and macropore placement, along with improving permeability to facilitate the transport of oxygenated irrigation water, is essential for simultaneously suppressing both gases. Field-scale validation is necessary to assess feasibility for sustainable rice farming.