Assessing anodic microbial populations and membrane ageing in a pilot microbial electrolysis cell

San-Martín, María Isabel; Sotres, Ana; Alonso, Raúl M.; Díaz, J. A.; Morán, Antonio; Escapa, Adrián

doi:10.1016/j.ijhydene.2019.01.287

Cited by 46 publications

(26 citation statements)

References 48 publications

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“…Stainless steel has been widely used as cathode material in large scale MECs. Of the eight different pilots reported in Table 1, seven used stainless steel cathodes [39,[43][44][45]48,49,51]. Furthermore, phosphate is contained in many electrolytes used in the laboratory to develop microbial anodes, which makes this system highly suitable for MECs [169].…”

Section: Cathode Materials and Homogeneous Catalysis Of Hydrogen Evolumentioning

confidence: 99%

Microbial electrolysis cell (MEC): Strengths, weaknesses and research needs from electrochemical engineering standpoint

et al. 2020

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Microbial electrolysis cells (MECs) produce hydrogen at the cathode associated with the oxidation of organic matter at the anode. This technology can produce hydrogen by consuming less electrical energy than water electrolysis does. However, it has been very difficult so far to scale up efficient MECs beyond the size of small laboratory cells. This article firstly revisits the fundamentals of MECs to assert their theoretical advantages. The low formal equilibrium cell voltage of 0.123 V and electrical and thermal energy yields as high as 10 and 12, respectively, are major assets. Other theoretical strengths are discussed, including the possibility to produce methane, and some safety advantages. The experimental achievements at pilot scale (several litres volume) are analysed through the prism of electrochemical engineering. This analysis leads to recommendations to modify some research efforts, notably by giving priority to increasing current density rather than working with volumetric parameters, using Faradaic yields to detect dysfunctions, and systematizing control experiments at open circuit. The critical analysis successively addresses electrolytes, electrode kinetics, temperature, substrate concentration, reactor architecture, and control procedures. It brings to light intrinsic weaknesses of the MEC concept and identifies improvements that can be made using current technology, for instance, by the catalysis of hydrogen evolution at neutral pH. The problem of the low electrolyte conductivity is pointed out and, in return, how increasing it can be detrimental to the key issue of anode acidification. Finally, research lines are proposed with the objective of moving ahead towards MEC development.

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Section: Cathode Materials and Homogeneous Catalysis Of Hydrogen Evolumentioning

confidence: 99%

Microbial electrolysis cell (MEC): Strengths, weaknesses and research needs from electrochemical engineering standpoint

et al. 2020

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“…However, high strength wastewaters produce more energy, therefore can be more economically viable in terms of energy production, as higher organic loads contain higher energy potential. A normalised net energy production of 76.2 kWh/m 3 /day was achieved for pig slurry, a high strength wastewater, at a volume of 16 L and an anodic and cathodic surface area of 11.25 m 2 /m 3 [39]. However, as for low strength wastewater, (<250 mg/L COD), even though it has a low HRT, it is still difficult to make treatment economically viable due to the very low energy production associated with its lower organics content.…”

Section: Feedstockmentioning

confidence: 99%

Microbial Electrolysis Cells for Decentralised Wastewater Treatment: The Next Steps

Fudge

Bulmer²,

Bowman³

et al. 2021

Water

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Traditional wastewater treatment methods have become aged and inefficient, meaning alternative methods are essential to protect the environment and ensure water and energy security worldwide. The use of microbial electrolysis cells (MEC) for wastewater treatment provides an innovative alternative, working towards circular wastewater treatment for energy production. This study evaluates the factors hindering industrial adoption of this technology and proposes the next steps for further research and development. Existing pilot-scale investigations are studied to critically assess the main limitations, focusing on the electrode material, feedstock, system design and inoculation and what steps need to be taken for industrial adoption of the technology. It was found that high strength influents lead to an increase in energy production, improving economic viability; however, large variations in waste streams indicated that a homogenous solution to wastewater treatment is unlikely with changes to the MEC system specific to different waste streams. The current capital cost of implementing MECs is high and reducing the cost of the electrodes should be a priority. Previous pilot-scale studies have predominantly used carbon-based materials. Significant reductions in relative performance are observed when electrodes increase in size. Inoculation time was found to be a significant barrier to quick operational performance. Economic analysis of the technology indicated that MECs offer an attractive option for wastewater treatment, namely greater energy production and improved treatment efficiency. However, a significant reduction in capital cost is necessary to make this economically viable. MEC based systems should offer improvements in system reliability, reduced downtime, improved treatment rates and improved energy return. Discussion of the merits of H2 or CH4 production indicates that an initial focus on methane production could provide a stepping-stone in the adoption of this technology while the hydrogen market matures.

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“…The protons hence produced travel through the proton exchange membrane (PEM) towards the cathodic terminal, and these protons are then reduced by electrons transferred through the external electrical circuit to produce hydrogen finally [144]. It was observed in a study that the MEC system cannot function spontaneously and that an additional energy source is needed to drive the reaction [148]. Any electrons hence digested by the exoelectrogens can be utilized at the anodic terminal of the MEC.…”

Section: Microbial Electrolysis For Hydrogen-reactors Design and Recementioning

confidence: 99%

A Comprehensive Understanding of Electro-Fermentation

et al. 2020

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Electro-fermentation (EF) is an upcoming technology that can control the metabolism of exoelectrogenic bacteria (i.e., bacteria that transfer electrons using an extracellular mechanism). The fermenter consists of electrodes that act as sink and source for the production and movement of electrons and protons, thus generating electricity and producing valuable products. The conventional process of fermentation has several drawbacks that restrict their application and economic viability. Additionally, metabolic reactions taking place in traditional fermenters are often redox imbalanced. Almost all metabolic pathways and microbial strains have been studied, and EF can electrochemically control this. The process of EF can be used to optimize metabolic processes taking place in the fermenter by controlling the redox and pH imbalances and by stimulating carbon chain elongation or breakdown to improve the overall biomass yield and support the production of a specific product. This review briefly discusses microbe-electrode interactions, electro-fermenter designs, mixed-culture EF, and pure culture EF in industrial applications, electro methanogenesis, and the various products that could be hence generated using this process.

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Assessing anodic microbial populations and membrane ageing in a pilot microbial electrolysis cell

Cited by 46 publications

References 48 publications

Microbial electrolysis cell (MEC): Strengths, weaknesses and research needs from electrochemical engineering standpoint

Microbial electrolysis cell (MEC): Strengths, weaknesses and research needs from electrochemical engineering standpoint

Microbial Electrolysis Cells for Decentralised Wastewater Treatment: The Next Steps

A Comprehensive Understanding of Electro-Fermentation

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