Pyrolysed almond shells used as electrodes in microbial electrolysis cell

9 p.The large cost of components used in microbial electrolysis cell (MEC) reactors represents an important limitation that is delaying the commercial implementation of this technology. In this work, we explore the feasibility of using pyrolysed almond shells (PAS) as a material for producing low-cost anodes for use in MEC systems. This was done by comparing the microbial populations that developed on the surface of PAS bioanodes with those present on the carbon felt (CF) bioanodes traditionally used in MECs. Raw almond shells were pyrolysed at three different temperatures, obtaining the best conductive material at the highest temperature (1000 °C). The behaviour of this material was then verified using a single-chamber cell. Subsequently, the main test was carried out using two-chamber cells and the microbial populations extant on each of the bioanodes were analysed. High-throughput sequencing of the 16S rRNA gene for eubacterial populations was carried out in order to compare the microbial communities attached to each type of electrode. The microbial populations on each electrode were also quantified by real-time polymerase chain reaction (realtime PCR) to determine the amount of bacteria capable of growing on the electrodes’surface. The results indicated that the newly developed PAS bioanodes possess a biofilm similar to those found on the surface of traditional CF electrodes. This research was possible thanks to the financial support of the Junta de Castilla y León, and was financed by European Regional Development Funds (LE320P18). C. B. thanks the Spanish Ministerio de Educación, Cultura y Deporte for support in the form of an FPI fellowship grant (Ref #: BES-2016-078329)

Impact of dissolved carbon dioxide concentration on the process parameters during its conversion to acetate through microbial electrosynthesis

© 2018 The Royal Society of Chemistry. The reduction of carbon dioxide (CO2) released from industry can help to reduce the emissions of greenhouse gases (GHGs) to the atmosphere while at the same time producing value-added chemicals and contributing to carbon fixation. Microbial electrosynthesis (MES) is a recently developed process which accomplishes this idea by using cathodic bacteria at the expense of only minimum energy. In this study, enriched mixed homoacetogenic bacteria as cathodic biocatalysts for the reduction of CO2 with five different concentrations were evaluated to produce acetate at a constant potential. Increasing the carbon concentration showed an improved acetate production rate and carbon conversion efficiency. A maximum acetate production rate of 142.2 mg L per day and a maximum carbon conversion efficiency of 84% were achieved, respectively, at 4.0 and 2.5 g HCO3- L-1. The changes in pH due to interactive reactions between the bicarbonate (substrate) and acetate (products) were able to create a buffering nature in the catholyte controlling the operating parameters of the MES process, such as pH and substrate specificity. A higher acetate production shifted the catholyte pH toward acidic conditions, which further triggered favorable conditions for the bioelectrochemical reduction of acetate to ethanol.G. Mohanakrishna gratefully acknowledges the Marie-Curie Intra-European Fellowship (IEF) supported project BIO-ELECTRO-ETHYLENE (Grant No: 626959) from the European Commission