Comparative performance of sustainable anode materials in microbial fuel cells (MFCs) for electricity generation from wastewater

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Abstract

Microbial fuel cells (MFCs) are a promising technology to generate electricity from wastewater and reduce the organic content. Whilst there has been a significant enhancement in MFC efficiency arising from the introduction of novel materials and cell designs, challenges remain with respect to the performance, cost, and sustainability of anode materials. This paper reports the development of single chamber MFCs with a focus on novel, cost- effective, and recycled carbon-based anode materials, including Recycled Water Filter Block/Powder (RWFB/ RWFP), Recycled Chopped Carbon Fibre (RCCF), Carbon Felt (CF) and Graphite Flexible powder (GFG). Anodes prepared from GFG were shown to provide high power density (342.8 mW/m2), followed by RCCF, CF, RWFP, RWFB and CF (77.6, 71.8, 59.0 and 57.9 mW/m2, respectively). Chemical Oxygen Demand (COD) reduction was measured initially and at day 30, with GFG anodes observed to remove 83% of the initial load, compared to RCCF, RWFB, RWFP and CF anodes, where COD reductions of 69%, 61%, 65% and 73% were observed, respectively. Electrochemical analysis and biofilm imaging confirmed recycled materials were colonised by microorganisms and performed to high standards. GFG offers significant promise as an anode material, with excellent performance supported by a reduction in capital cost of up to 90% in comparison to CF. The use of recycled carbon material as MFC anodes shows promise, but requires additional work to improve the stability and durability of systems to permit scale-up.
Original languageEnglish
Article number101385
Pages (from-to)1-12
Number of pages12
JournalResults in Engineering
Volume20
Issue number101385
Early online date15 Sept 2023
DOIs
Publication statusPublished (in print/issue) - 31 Dec 2023

Bibliographical note

Funding Information:
The authors are thankful to Horizon 2020 ALICE project for the financial support provided. ALICE project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 734560. This publication reflects only the authors' view and the Research Executive Agency, REA, is not responsible for any use that may be made of the information it contains. This research work was also carried out as part of the Royal Society and National Natural Science Foundation of China (IEC\NSFC\201070).

Funding Information:
Microbial fuel cells (MFCs) are a promising technology to generate electricity from wastewater and reduce the organic content. Whilst there has been a significant enhancement in MFC efficiency arising from the introduction of novel materials and cell designs, challenges remain with respect to the performance, cost, and sustainability of anode materials. This paper reports the development of single chamber MFCs with a focus on novel, cost-effective, and recycled carbon-based anode materials, including Recycled Water Filter Block/Powder (RWFB/RWFP), Recycled Chopped Carbon Fibre (RCCF), Carbon Felt (CF) and Graphite Flexible powder (GFG). Anodes prepared from GFG were shown to provide high power density (342.8 mW/m2), followed by RCCF, CF, RWFP, RWFB and CF (77.6, 71.8, 59.0 and 57.9 mW/m2, respectively). Chemical Oxygen Demand (COD) reduction was measured initially and at day 30, with GFG anodes observed to remove 83% of the initial load, compared to RCCF, RWFB, RWFP and CF anodes, where COD reductions of 69%, 61%, 65% and 73% were observed, respectively. Electrochemical analysis and biofilm imaging confirmed recycled materials were colonised by microorganisms and performed to high standards. GFG offers significant promise as an anode material, with excellent performance supported by a reduction in capital cost of up to 90% in comparison to CF. The use of recycled carbon material as MFC anodes shows promise, but requires additional work to improve the stability and durability of systems to permit scale-up.In keeping with the low-cost theme for this investigation, a 3.6 cm internal diameter Polyvinyl Chloride (PVC) pipe was used to create a single chamber membrane-less cube type MFC of 50 mL volume (Fig. 1). The chamber was sealed at one end with an acrylic support plate (6 cm by 6 cm) and a second acrylic plate (6 cm by 6 cm having a 3 cm hole at the centre) was used to support a polyester cloth forming the air cathode (Fig. 1). Rubber gaskets and mechanical support structure ensured the mechanical integrity of the system; no leakage of contents was observed. Four holes were drilled into the cylindrical surface of the reactor to enable the connection of the electrodes (anode and cathode), insertion of the reference electrode and a sample collection port. Rubber septa were utilised to ensure anaerobic conditions within the chamber. Using the methods described by Yang et al. [23], MFCs cathodes were prepared by mixing activated carbon (AC) powder, carbon black (CB) and a poly (vinylidene fluoride) (PVDF) binder (Redox, Sweden) to form a paste which was supported on Stainless-Steel Mesh size 60 (SSM60) - used as both the current collector and support material.Graphite flexible powder (GFG) (SGL, Germany) and RCCF were also processed into anodes. GFG powder was combined with SA to form a paste prior to deposition on a SSM60 support as described above. For RCCF anode fabrication, the collected fibre was chopped into lengths of 0.5–1 cm, whereby the paste with SA was prepared prior to deposition into a SSM60 support.The performance of GFG based anodes offers significant potential and from a cost perspective, anodes can be fabricated with the use of a stainless-steel mesh support material and sodium alginate (SA) at a total manufacturing cost of £65/m2-approximately an order of magnitude (90%) lower than the cost of a standard carbon based MFC, e.g. CF ranges in price from £635 to £794/m2 [21]. Recycled, biocompatible and conductive materials, such as recycled chopped carbon fibres or recycled water filters may be available at low/no cost, but preparation or pre-treatment can be required before anode fabrication. Fig. 9 shows the normalised cost (per m2) of anodes for MFC, with RCCF demonstrating a cost reduction of up to 87% when compared to CF. The cost associated with RWFP is solely the anode support and preparation cost, demonstrating a 93% cost reduction vs CF.

Publisher Copyright:
© 2023 The Authors

Keywords

  • Microbial fuel cells
  • Anodes
  • Recycled anode materials
  • Flexible graphite powder
  • Wastewater

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