• Energy Research

In this work, the performance of dual-chamber microbial fuel cells (MFCs) constructed either with commonly used Nafion® proton exchange membrane or supported ionic liquid membranes (SILMs) was assessed. The behavior of MFCs was followed and analyzed by taking the polarization curves and besides, their efficiency was characterized by measuring the electricity generation using various substrates such as acetate and glucose. By using the SILMs containing either [C6mim][PF6] or [Bmim][NTf2] ionic liquids, the energy production of these MFCs from glucose was comparable to that obtained with the MFC employing polymeric Nafion® and the same substrate. Furthermore, the MFC operated with [Bmim][NTf2]-based SILM demonstrated higher energy yield in case of low acetate loading (80.1 J g-1 CODin m-2 h-1) than the one with the polymeric Nafion® N115 (59 J g-1 CODin m-2 h-1). Significant difference was observed between the two SILM-MFCs, however, the characteristics of the system was similar based on the cell polarization measurements. The results suggest that membrane-engineering applying ionic liquids can be an interesting subject field for bioelectrochemical system research.

Excess consumption of energy by humans is compounded by environmental pollution, the greenhouse effect and climate change impacts. Current developments in the use of algae for bioenergy production offer several advantages. Algal biomass is hence considered a new bio-material which holds the promise to fulfil the rising demand for energy. Microalgae are used in effluents treatment, bioenergy production, high value added products synthesis and CO2 capture. This review summarizes the potential applications of algae in bioelectrochemically mediated oxidation reactions in fully biotic microbial fuel cells for power generation and removal of unwanted nutrients. In addition, this review highlights the recent developments directed towards developing different types of microalgae MFCs. The different process factors affecting the performance of microalgae MFC system and some technological bottlenecks are also addressed.

Abstract In this study, a novel miniature terrestrial microbial fuel cells (TMFCs) inoculated with commercial garden soil was developed to generate bioelectricity. The startup and stabilization were evaluated as open circuit voltage (OCV). The effect of an enrichment procedure with 12 mM, 37 mM, and 61 mM Na-acetate under anaerobic conditions was assessed. The initial OCV was 0.55 ± 0.02 V, 0.58 ± 0.01 V and 0.75 ± 0.15 V in the TMFCs inoculated with 12 mM, 37 mM and 61 mM Na-acetate, respectively. The OCV increased in relation with the substrate input. The average OCV during stable operation was as follows: 1.01 ± 0.006 V (12 mM), 1.02 ± 0.005 V (37 mM) and 1.13 ± 0.003 V (61 mM). The time required for peaking the maximum voltage and its stabilization was significantly decreased up to ~2 h. Hence, it is concluded that the OCV output of the miniature TMFCs was comparable or even higher than macroscale reactors and it is optimal for rapid detection of the electrogenic process in soil samples. Furthermore, the reactor design displayed simplicity and the electrode area to reactor volume ratio was enhanced in contrast to macroscale TMFCs.

A Gas Separation Membrane Bioreactor (GSMBR) by integrating membrane technology with a continuous biohydrogen fermenter was designed. The feasibility of this novel configuration for the improvement of hydrogen production capacity was tested by stripping the fermentation liquor with CO2- and H2-enriched gases, obtained directly from the bioreactor headspace. The results indicated that sparging the bioreactor with the CO2-concentrated fraction of the membrane separation unit (consisting of two PDMS modules) enhanced the steady-state H2 productivity (8.9–9.2 L H2/L-d) compared to the membrane-less control CSTR to be characterized with 6.96–7.35 L H2/L-d values. On the other hand, purging with the H2-rich gas strongly depressed the achievable productivity (2.7–3.03 L H2/L-d). Microbial community structure and soluble metabolic products were monitored to assess the GSMBR behavior. The study demonstrated that stripping the bioH2 fermenter with its own, self-generated atmosphere after adjusting its composition (to higher CO2-content) can be a promising way to intensify dark fermentative H2 evolution.

In this study, microbial fuel cells deploying heterogeneous ion exchange membranes were assessed. The behavior of the cells as a function of the membrane applied was evaluated in terms of maximal current density, electron recovery efficiency and energy production rate (up to 427.5 mA, 47.7 % and 660 J m-2h-1, respectively) at different substrate (acetate) feedings (2.15 - 8.6 mM). System performance was characterized in the light of oxygen and acetate crossovers. The effect of membranes (in relation to the oxygen mass transfer coefficient, kO) on the microbial diversity of anodic and membrane-surface biofilms was investigated. Based on the relative abundance of bacterial orders, the two populations could be distinguished and membranes with larger kO tended to promote more the air-tolerant microbes in the biofouling layer. This indicates that membrane kO has a direct effect on membrane foulant microbial composition, and thus, on the expected time-stability of the membrane.

Abstract This review portrays the status and perspectives of bioaugmented hydrogen fermentation, an emerging strategy of process intensification. Firstly, the paper introduces the potentials and limitations of dark fermentative hydrogen production and describes the technologies available for its enhancement including bioaugmentation. The theoretical background and practical features of augmentation methods for biohydrogen generation are subsequently assessed and surveyed in details. Furthermore, a throughout evaluation of the recent and novel achievements reported in the concept of “augmented hydrogen fermentation” is given in association with (i) bioreactor start-up, (ii) utilization of solid wastes, wastewaters, (iii) the feasibility in continuous systems as well as in complementary – integrated – applications. The article is intended to provide an insight to the advancements made for realizing more viable biohydrogen formation via bioaugmentation and hence it might be encouraging for further studies in the field.