Bioelectromethanogenesis reaction in a tubular Microbial Electrolysis Cell (MEC) for biogas upgrading

The utilization of a pilot scale tubular Microbial Electrolysis Cell (MEC), has been tested as an innovative biogas upgrading technology. The bioelectromethanogenesis reaction permits the reduction of the CO2 into CH4 by using a biocathode as electrons donor, while the electroactive oxidation of organic matter in the bioanode partially sustains the energy demand of the process. The MEC has been tested with a synthetic wastewater and biogas by using two different polarization strategies, i.e. the three-electrode configuration, in which a reference electrode is utilized to set the potential at a chosen value, and a two-electrode configuration in which a fixed potential difference is applied between the anode and the cathode. The tubular MEC showed that the utilization of a simple two electrode configuration does not allow to control the electrodic reaction in the anodic chamber, which causes the increase of the energy consumption of the process. Indeed, the most promising performances regarding the COD and CO2 removal have been obtained by controlling the anode potential at +0.2 V vs SHE with a three electrode configuration, with an energy consumption of 0.47 kWh/kgCOD and 0.33 kWh/Nm3 of CO2 removed, which is a comparable energy consumption with respect the available technologies on the market

Production of Short-chain Fatty Acid from CO2 Through Mixed and Pure Culture in a Microbial Electrosynthesis Cell

The continuous accumulation of atmospheric CO2 requires the development of new technologies for its mitigation. Carbon capture and utilization (CCU) technologies aim to convert CO2 into precious compounds like chemicals and fuels. Biological fixation is an attractive CCU strategy in terms of cost, sustainability and variety of products. Chemoautotrophic microorganisms such as methanogens and acetogens are able to reduce CO2 into acetate and methane, respectively. Acetogens bacteria are able to use CO2 for cell growth through the Wood Liujhundal pathway, moreover, the final precursor (i.e. Acetyl-CoA) of the autotrophic metabolism, is also used in energy metabolism with acetate production as a waste product. Furthermore, it is possible to obtain multicarbon products of autotrophic origin starting from acetyl-CoA and acetate. The biotechnological use of these microorganisms requires the presence of H2 as substrate, which is used as an electron donor in the pathway. This reaction can be sustained by a biocathode in a microbial electrosynthesis cell, in which the reducing power is generated by a polarized electrode. This study proposes the use of a microbial electrosynthesis cell for conversion to acetate in H-cells by either a mixed culture enriched with Acetobacterium woodii or a pure culture of Acetobacterium woodii, to observe the difference in terms of acetate production and reducing power consumption efficiency. The mixed culture was obtained from a mixture of activated sludge and anaerobic digestate, treated by a protocol capable to select acetogenic microorganisms without the use of specific chemical inhibitors (2-Bromoethanesulfonate). Both inoculums were tested at room temperature (25°C) in the cathodic chamber of the H-cell at potentials in the range of -0.7 to -1.1 V vs SHE. The obtained results showed that the enriched mixed culture produced at -0.7 vs SHE a mixture of volatile fatty acids including C4 and C5 molecules with an overall coulombic efficiency of 50%, while at the potential of -0.9 vs SHE methane constituted the main product of the biocathode. The pure culture, on the other hand, showed a specific production of acetate with a coulombic efficiency of 44% at -0.9 vs SHE and 63% at -1.1 vs SHE. Furthermore, a drastic decrease in biocathode biomass was observed in pure culture, suggesting a higher tendency to form biofilms on the electrode unlike the mixed culture, which showed a standard growth profile in the bulk

Minimal Symptom Expression' in Patients With Acetylcholine Receptor Antibody-Positive Refractory Generalized Myasthenia Gravis Treated With Eculizumab

The efficacy and tolerability of eculizumab were assessed in REGAIN, a 26-week, phase 3, randomized, double-blind, placebo-controlled study in anti-acetylcholine receptor antibody-positive (AChR+) refractory generalized myasthenia gravis (gMG), and its open-label extension

T-REX OU4 HIRES: the high resolution spectrograph for the E-ELT

The goal of this unit was to consolidate the project for the construction of the high resolution spectrometer of the E-ELT (HIRES). The task included the development of scientific cases and tools to predict the instrumental performances. From the technical point of view it included several R&D activities in collaboration with highly specialized Italian companies; it culminated with the detailed design of a highly modular instrument based on well established technologies. From the management point of view it lead to the consolidation of a large international consortium that spans over 12 countries and includes most of the European and ESO-related institutes interested in high resolution spectroscopy. This consortium is led by INAF; its formal creation is awaiting the official call by ESO for the phase-A study for the HIRES instrument of the E-ELT

Electron recycle concept in a microbial electrolysis cell for biogas upgrading

Abstract An innovative strategy to control the metabolism of microorganisms is offered by bioelectrochemical systems in which a graphite-based cathode can be used as electron donor or acceptor. An advanced microbial electrolysis cell is developed to combine CO2 removal from a synthetic biogas in a biocathode and the organic matter oxidation in a bioanode. A novel biogas upgrading approach is presented in which an electron recycle concept is obtained by the combination of CO2 reduction and oxidation. While the bioelectrochemical anodic chemical oxygen demand oxidation provides the electrons necessary for the cathodic CO2 reduction into methane and acetate, the acetate produced by acetogenic microorganisms migrates from the cathode to the anode being oxidized again by the bioanode

Carbon dioxide abatement and biofilm growth in Mec equipped with a packed bed adsorption column

In this study, a lab-scale microbial electrolysis cell (MEC) aimed to the biogas upgrading through a methanogenic biocathode has been integrated with an adsorption column to test the possible increase of the biocathode CO2 removal capacity. In the adopted MEC configuration, the oxidation of the organic matter by an anodic biofilm was utilized to partially sustain the energy demand of the bioelectromethanogenesis reaction in the cathodic chamber. Anodic and cathodic biofilms were characterized by cyclic voltammetry (CV) technique which allowed the electron transfer mechanisms characterization in the anodic and cathodic bioelectrochemical reactions. More in detail, while the anodic biofilm showed the presence of a potential direct electron transfer, the cathodic CV suggests a hydrogen mediated mechanism for the CO2 reduction into CH4. The integration of a sorption column and the MEC biocathode showed a negligible effect in the overall biocathode CO2 removal, suggesting the control of the CO2 sorption by a chemical reaction through the alkalinity generation mechanism instead of the gas-liquid mass transfer

Potentiostatic vs galvanostatic operation of a Microbial Electrolysis Cell for ammonium recovery and biogas upgrading

The experimental study reports the performance of a three-chamber Microbial Electrolysis Cell equipped with a two-side cathode, which combines the COD removal in the intermediate anodic chamber, the CO2 removal from a gas mixture in the two-side cathode and the recovery of ammonium as a concentrate solution. The MEC anode was fed by a synthetic dark fermentation effluent with a nitrogen load rate of 1.7 g N/Ld while the two-side cathode was operated with a gas mixture containing CO2. Indeed, the MEC configuration permitted the CO2 removal maximization from a N2/CO2 gaseous mixture simulating a biogas in terms of carbon dioxide composition, while the ammonium migration through the cation exchange membrane allowed for the recovery of a 5 times concentrated solution of ammonium. The +0.20 V vs SHE potentiostatic anodic condition and the two different galvanostatic conditions allowed the removal of 4.21 gCO2/Ld while 700 mg N/Ld were recovered as a concentrated ammonium solution. The current increase set by galvanostatic operation promoted the CO2 removal and ammonium recovery increase by the 113 % and 27 % in comparison with the potentiostatic condition. An increase of the energy consumption was promoted by the galvanostatic condition due to the loss of bioelectrochemical COD oxidation in favour of water oxidation which in turn was caused by the anodic overpotential decrease from 0.85 to 0.52 V

Role of the organic loading rate and the electrodes’ potential control strategy on the performance of a micro pilot tubular microbial electrolysis cell for biogas upgrading

An innovative biogas upgrading process consists in the utilization of a microbial electrolysis cell (MEC) in which a biocathode performs the bioelectromethanogenesis reaction reducing the CO2 into CH4 while an additional CO2 removal mechanism consists in the CO2 sorption as HCO3 , due to alkalinity generation in the catholyte. Here, a two chamber 12-liter tubular MEC has been developed to upgrade biogas by using bioelectrochemical organic matter oxidation at the anode to partially sustain the energy demand of the process. In the tubular MEC, the electroactive microorganisms’ selection was obtained by polarizing the anode chamber at + 0.2 V vs. SHE (Standard Hydrogen Electrode). Under this condition, three values of the applied organic loading rate (OLR) have been investigated. Once the best OLR was selected at 2.55 gCOD/Ld, the potentiostatic control of the tubular MEC was switched from the anode to the cathode. As reported in a previous experiment, the potentiostatic control shift resulted in a sharp decrease of the process’ energy consumption thanks to minimization of the anodic overpotential. Moreover, three different runs were conducted with the cathodic potential controlled at 1.3 V; 1.8 V; 2.3 V vs. SHE to investigate the performances of the CO2 abatement. The lowest energy consumption for CO2 removal was obtained during the 1.3 V vs SHE condition with a consumption of 0.5 kWh/ Nm3 of removed CO2. Those results indicate that the potentiostatic control switch from the anode to the cathode permits to minimize the energy consumption of a micro pilot MEC having a tubular configuration

Autotrophic Acetate Production under Hydrogenophilic and Bioelectrochemical Conditions with a Thermally Treated Mixed Culture

Bioelectrochemical systems are emerging technologies for the reduction in CO2 in fuels and chemicals, in which anaerobic chemoautotrophic microorganisms such as methanogens and acetogens are typically used as biocatalysts. The anaerobic digestion digestate represents an abundant source of methanogens and acetogens microorganisms. In a mixed culture environment, methanogen’s inhibition is necessary to avoid acetate consumption by the presence of acetoclastic methanogens. In this study, a methanogenesis inhibition approach based on the thermal treatment of mixed cultures was adopted and evaluated in terms of acetate production under different tests consisting of hydrogenophilic and bioelectrochemical experiments. Batch experiments were carried out under hydrogenophilic and bioelectrochemical conditions, demonstrating the effectiveness of the thermal treatment and showing a 30 times higher acetate production with respect to the raw anaerobic digestate. Moreover, a continuous flow bioelectrochemical reactor equipped with an anion exchange membrane (AEM) successfully overcomes the methanogens reactivation, allowing for a continuous acetate production. The AEM membrane guaranteed the migration of the acetate from the biological compartment and its concentration in the abiotic chamber avoiding its consumption by acetoclastic methanogenesis. The system allowed an acetate concentration of 1745 ± 30 mg/L in the abiotic chamber, nearly five times the concentration measured in the cathodic chamber