Investigation of the Microbial Community Structure of Peat and Saltmarsh Plant Microbial Fuel Cells

Wandre, Anosh Satish (2023) Investigation of the Microbial Community Structure of Peat and Saltmarsh Plant Microbial Fuel Cells. Masters by Research thesis (MPhil), Manchester Metropolitan University.

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Abstract

Pressure for the advancement of renewable energy is increasing with the continued rise in global temperature, world population and energy demand. Plant microbial fuel cells (PMFCs) are one of the possible solutions in development to assist in solving the problem. PMFCs function by harnessing electrons released from the metabolic activity of microorganisms. PMFCs have many advantages over other renewable sources of electricity, for example, implementation into green roofs and rice paddy fields, satisfying two functions without the need for additional space. In this study, PMFCs in saltmarsh and peatlands were investigated. Calluna vulgaris and Puccinellia maritima were chosen as plant species in this study along with sediment microbial fuel cells (SMFCs) for each soil type (peat and saltmarsh). Using a dual-chamber design, the fuel cell’s voltage, current and power were observed for over 150 days after which they were destructively sampled to analyse soil chemistry, microbial community-level physiological profiling and microbial community analysis using next-generation sequencing. Overall, both planted and non-planted saltmarsh fuel cells outperformed the peat fuel cells. The greatest maximum power output was measured at 0.086mW/m2 by saltmarsh non-planted while the peat systems, peat planted with C. vulgaris peaked at 0.043mW/m2. Significantly higher concentrations of Na were detected in samples taken from saltmarsh fuel cells over peat fuel cells. This was attributed to the high concentration of Na and is likely linked to NaCl concentrations in the saltmarsh fuel cells. Higher concentrations of NaCl have been linked to increase transfer of electrons and an increase in MFC performance (Lefebvre et al., 2012). Comparing planted and non-planted systems within the same soil type showed no difference indicating that Calluna vulgaris and Puccinellia maritima and subsequently plant root exudates have no effect on the generation of electricity. In these systems, the primary influence on electricity generation is soil processes. The combination of higher relative abundance of Bacillus, Geopsychrobacter and Geothix and the likely high concentrations of NaCl in saltmarsh systems is the primary contributor to the higher generation of power compared to peat systems. With further research, there is great potential for small-scale power generation with sustainability in mind with PMFCs and SMFCs.