Abstract
In this paper, we tested the combined use of a biochar-based material at the cathode and of Pseudomonas aeruginosa strain in a single chamber, air cathode microbial fuel cells (MFCs) fed with a mix of shredded vegetable and phosphate buffer solution (PBS) in a 30% solid/liquid ratio. As a control system, we set up and tested MFCs provided with a composite cathode made up of a nickel mesh current collector, activated carbon and a single porous poly tetra fluoro ethylene (PTFE) diffusion layer. At the end of the experiments, we compared the performance of the two systems, in the presence and absence of P. aeruginosa, in terms of electric outputs. We also explored the potential reutilization of cathodes. Unlike composite material, biochar showed a life span of up to 3 cycles of 15 days each, with a pH of the feedstock kept in a range of neutrality. In order to relate the electric performance to the amount of solid substrates used as source of carbon and energy, besides of cathode surface, we referred power density (PD) and current density (CD) to kg of biomass used. The maximum outputs obtained when using the sole microflora were, on average, respectively 0.19 Wm−2kg−1 and 2.67 Wm−2kg−1, with peaks of 0.32 Wm−2kg−1 and 4.87 Wm−2kg−1 of cathode surface and mass of treated biomass in MFCs with biochar and PTFE cathodes respectively. As to current outputs, the maximum values were 7.5 Am−2 kg−1 and 35.6 Am−2kg−1 in MFCs with biochar-based material and a composite cathode. If compared to the utilization of the sole acidogenic/acetogenic microflora in vegetable residues, we observed an increment of the power outputs of about 16.5 folds in both systems when we added P. aeruginosa to the shredded vegetables. Even though the MFCs with PTFE-cathode achieved the highest performance in terms of PD and CD, they underwent a fouling episode after about 10 days of operation, with a dramatic decrease in pH and both PD and CD. Our results confirm the potentialities of the utilization of biochar-based materials in waste treatment and bioenergy production.
Highlights
Bioenergy is a promising and feasible alternative to fossil fuels and a sustainable waste management solution
We investigated the effect of the addition of a Pseudomonas aeruginosa ATCC 15,692 strain to the microflora naturally occurring in the organic residues, mainly composed by Lactobacillaceae and Bacillaceae on microbial fuel cells (MFCs) performance
power density (PD) and current density (CD) in comparison to the composite, the possibility to use it for more than one cycle and, to recycle the cathode itself as a soil fertility improver represents an advantage in comparison to more complex and expensive materials like nickel-mesh-activated-carbon and poly tetra fluoro ethylene (PTFE)-layer electrodes
Summary
Bioenergy is a promising and feasible alternative to fossil fuels and a sustainable waste management solution. The scientific community is working hard to discover and develop low-cost materials that may substantially enhance the performance of microbial fuel cells (MFCs) and expand their applications in waste and wastewater treatment [1,2,3,4,5,6,7,8,9]. All the above-mentioned processes are promising and are able to contribute to the transition to the circular economy and sustainable development [2,19,20,21]
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