Evaluation of cost effective and recycled anode materials in microbial electrolysis cells for hydrogen production from wastewater

Abstract

The production of hydrogen from wastewater is regarded as a viable method for the generation of sustainable energy. H2 synthesis by microbial electrolysis cells (MECs) shows significant advantages over conventional fossil fuel-based hydrogen production methods, however, the anode material and structure are critical to the overall efficiency of the MEC. When the influent water enters the MEC, the microorganisms present in the wastewater, mainly electrochemically active bacteria, degrade organic matter, proliferate and establish a biofilm on the anode surface. These bacteria transfer ions/electrons to the anode with protons transported to the cathode where subsequent reduction reactions produce H2. Given the input of energy from the biofilm, only a small external bias is needed to drive hydrogen production. For these reasons, the anode must be conductive, biocompatible, and economically viable to drive the scaling of this technology to commercialization. In terms of reactor design, a membrane-less single chamber cube design has been considered suitable for practical use due to its improved electrochemical performance and low capital cost.

Considering these issues, the goal of this dissertation was to identify cost-effective and recycled materials for MEC anodes, to compare their performance and cost, and through effective system design to optimise the anode's performance in terms of H2 production and chemical oxygen demand (COD) reduction.

Both microbial fuel cells (MFCs) and MECs were developed using graphite flexible powder (GFG), recycled water filter block/powder (RWFB/P), and recycled carbon fibre (RCCF) and carbon felt (CF) based anodes. Performance was compared in terms of electricity production (MFC), H2 generation (MEC) and COD reduction rate. GFG based system outperformed all other systems producing gas with a hydrogen composition of 61.96 ± 5.18%, at a volume of 0.280 ± 0.009 L/L/d H2.

Based on the lab data and using a Pugh based design approach, a concept design for a novel MEC was proposed to serve as a starting point to inspire further progress towards of commercialisation of MECs using cost-efficient and recycled a node materials.

Date of Award	May 2022
Original language	English
Sponsors	Department for the Economy
Supervisor	Patrick Dunlop (Supervisor), Neil Hewitt (Supervisor) & Caterina Brandoni (Supervisor)