Bioelectrochemical Systems for Energy Valorization of Waste Streams

Abstract

Bioelectrochemical systems (BES) encompass a group of technologies derived from conventional electrochemical systems in which the electrodic reactions are directly or indirectly linked to the metabolic activity of certain types of microorganisms. Although BES have not yet made the leap to the commercial scale, these technologies hold a great potential, as they allow to valorize different liquid and gas waste streams. This chapter is devoted to exploring some of the possibilities that BES offer in the management and valorization of wastes. More specifically, it focuses on analyzing practical aspects of using BES for energy valorization of wastewaters and CO 2-rich streams. Here, it is shown how BES can compete, in terms of energy usage, with conventional wastewater treatment technologies by exploiting the energy content of some of the chemicals present in the wastewater. Moreover, it explores how BES could enable using wastewater treatment plants as load regulation system for electrical grids. It also includes some insights on the capability of BES to recover valuable products such as fertilizers form wastes, a feature that allows this technology to promote energy efficiency in the fertilizers industry, and a sector that demands substantial amounts of energy in our world today. Finally, some of the most relevant scale-up experiences in the field are also covered.

Assessing the ageing process of cation exchange membranes in bioelectrochemical systems

“…BES are also capable of utilising a broad range of organic and inorganic substrates [2] which gives them a great operational flexibility. Despite that, and despite the numerous scale-up endeavours reported in the literature [3], BES are far from being a mature technology [4]. The still low current densities, relatively large capital cost and the difficulties associated with energy harvesting/management are often reported as major challenges in their way towards practical application.…”

Optimising the Hydraulic Retention Time in a Pilot-Scale Microbial Electrolysis Cell to Achieve High Volumetric Treatment Rates Using Concentrated Domestic Wastewater

“…The most common configurations of BESs are microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) [6]. As MECs are able to recover valuable hydrogen gas rather than electricity, it has been suggested that scaling up an MEC is more economically viable than scaling up an MFC [7,8].…”

Assessing the ageing process of cation exchange membranes in bioelectrochemical systems

“…BES are also capable of dealing with a broad range of organic and inorganic substrates [2] which gives them a great operational flexibility. Despite that, and despite the numerous scale-up experiences reported in the literature [3], BES are far from being a mature technology [4]. The still low current densities, relatively large capital cost and the difficulties associated with energy harvesting/management are often cited as major challenges in their way towards practical application [3].…”

“…Thus, it is not surprising that, in an effort to improve the commercial perspectives of BES, many researchers have come up with alternative designs that completely dispense with the membrane. Although many of them have proved to be successful in several fields of application such as organic and inorganic contamination removal [7,8] or energy production [9], the IEM becomes a critical element when the aim is to optimize energy efficiency (by avoiding oxygen and hydrogen crossover [4,6] ) or accomplish processes of industrial interest (nutrients recovery, microbial electrosynthesis or seawater desalination [10]). The application of several types of IEM such as anion exchange membranes (AEM), cation exchange membranes (CEM), microfiltration membrane, bipolar membrane and ultrafiltration membranes to BES has been extensively covered in the literature [6].…”

“…Membrane ageing is usually characterised in terms of physical, chemical and electrochemical stability and to this end, a vast array of methods is available including microscopy, impedance spectroscopy or titration technics. Previous studies have made use of these techniques to investigate the ageing of individual membranes [10,11], but there is a lack of knowledge on how these membranes compare in terms of their ageing patters a stability. In this study, we aim at filling this gap by assessing how the mechanical, chemical and electrochemical properties of five commercially available cation exchange membranes develop during four months of continuous operation within the environment of a microbial electrolysis cell (MEC).…”