Title : Plant microbial fuel cells for net zero emissions, renewable energy, green and sustainable remediation, and waste valorization
Abstract:
The world is facing a convergence of critical challenges, including energy scarcity, climate change, and pervasive environmental pollution. This study proposes an integrated and sustainable solution through the application of Plant Microbial Fuel Cells (PMFCs) across forestry, agricultural, and environmental systems. PMFCs exploit rhizosphere microorganisms to oxidize plant-derived organic compounds, generating electricity via bioelectrochemical reactions while simultaneously enhancing carbon sequestration, producing green energy, enabling heavy-metal remediation, and promoting waste valorization.
Wastewater treatment produces large quantities of sludge, and conventional disposal methods such as landfilling and incineration are energy-intensive and environmentally detrimental. Sintered sludge represents a sustainable alternative, converting waste into functional materials for energy-related applications. In parallel, increasing volumes of wood and plant waste pose growing environmental concerns, for which biochar offers an effective valorization pathway. Both sintered sludge and biochar are thermochemically derived materials with high potential for resource recovery.
Four case studies were conducted to evaluate PMFC performance under different valorization strategies. In Case Study 1, sintered sludge granules were employed as PMFC substrates using the native Taiwanese grass Spodiopogon formosanus Rendle. Soil-based PMFCs produced 100–200 mV, significantly outperforming soil microbial fuel cells without plants (20–30 mV). While 100% sludge-based MFCs exhibited rapid voltage decay, the corresponding PMFCs sustained stable outputs of 150–200 mV, highlighting the critical role of plant–microbe interactions in system stability.
Case Study 2 investigated arsenic-contaminated soil planted with Cyperus malaccensis Lam. ssp. monophyllus. (Vahl) T. Koyama. Biochar addition markedly enhanced microbial activity, plant growth, and electricity generation, achieving a peak voltage of 566 ± 13.21 mV while reducing soil arsenic concentrations from 70 mg/kg to 57.92 ± 0.01 mg/kg through synergistic phytoremediation and bioelectrochemical processes.
In Case Study 3, Ipomoea batatas (sweet potato leaves) was employed to evaluate long-term PMFC performance with varying ratios of sintered sludge and biochar. The soil–sludge mixture produced the highest average peak voltage (481.08 mV), attributed to mineral-rich sludge adjusting soil pH to conditions favorable for electroactive microbes.
Case Study 4 demonstrated the valorization of plant biomass waste through biorefinery processes, converting cellulose-rich feedstocks into levulinic acid, with yields of 2.5 ± 0.14% from reed rhizomes under optimized conditions.
Overall, this study demonstrates that PMFC systems integrated with valorized sludge, biochar, and biomass biorefinery technologies offer a promising pathway for clean energy generation, carbon reduction, environmental remediation, and circular resource utilization.
