LONG-TERM PLANT MICROBIAL FUEL CELL USING ELEOCHARIS PALUSTRIS

Abstract

Plant microbial fuel cells (PMFCs) have attracted increasing interest as alternative bio electrochemical systems due to their sustainability and environmental compatibility. This technology is based on the symbiosis between living plants and soil microorganisms. The rhizosphere-associated microbial community catalyses the degradation of plant root exudates, resulting in sustainable bioelectricity generation. The system performance is strongly influenced by several factors, including the plant species used and the sediment characteristics. Although many plant species have been tested in PMFCs, Eleocharis palustris has rarely been investigated for this application. This study evaluates the long-term performance of a PMFC utilizing Eleocharis palustris as a primary macrophyte, with sediment collected from Lake Mandrensko (Burgas, Bulgaria) serving as a microbial and electrochemical substrate. Sediment analysis showed elevated levels of organic matter and nutrients (COD - 3.6 g kg⁻¹, phosphate - 2.8 g kg⁻1, and manganese -
1.3 g kg⁻¹), supporting the metabolic activity of electrogenic bacteria and indicating the suitability of the sediment as a substrate for sustainable PMFC operation. The system was configured as a single-chamber bio-electrochemical reactor, featuring an anode embedded in the sediment and a cathode exposed to atmospheric oxygen. During the 80-day operational period, the system exhibited three distinct voltage phases: an initial adaptation phase (60 - 80 mV), a fluctuation phase (150 - 230 mV), and a final phase characterized by declining voltage and substrate depletion. A clear correlation between COD concentration and voltage output was observed, with the highest substrate level of 10.53 g COD dm⁻3 corresponding to a power density peak of 2339.34 mW m⁻³.