The use of electrochemically active bacteria to break down organic matter, combined with the addition of a small voltage (>0.2 V in practice) in specially designed microbial electrolysis cells (MECs), can result in a high yield of hydrogen gas. While microbial electrolysis was invented only a few years ago, rapid developments have led to hydrogen yields approaching 100%, energy yields based on electrical energy input many times greater than that possible by water electrolysis, and increased gas production rates. MECs used to make hydrogen gas are similar in design to microbial fuel cells (MFCs) that produce electricity, but there are important differences in architecture and analytical methods used to evaluate performance. We review here the materials, architectures, performance, and energy efficiencies of these MEC systems that show promise as a method for renewable and sustainable energy production, and wastewater treatment.

Microbial Electrolysis Cells for High Yield Hydrogen Gas Production from Organic Matter

Factors influencing fermentative hydrogen production: a review

Environmental pollution has been on the rise in the past few decades owing to increased human activities on energy reservoirs, unsafe agricultural practices and rapid industrialization. Amongst the pollutants that are of environmental and public health concerns due to their toxicities are: heavy metals, nuclear wastes, pesticides, green house gases, and hydrocarbons. Remediation of polluted sites using microbial process (bioremediation) has proven effective and reliable due to its eco-friendly features. Bioremediation can either be carried out ex situ or in situ, depending on several factors, which include but not limited to cost, site characteristics, type and concentration of pollutants. Generally, ex situ techniques apparently are more expensive compared to in situ techniques as a result of additional cost attributable to excavation. However, cost of on-site installation of equipment, and inability to effectively visualize and control the subsurface of polluted sites are of major concerns when carrying out in situ bioremediation. Therefore, choosing appropriate bioremediation technique, which will effectively reduce pollutant concentrations to an innocuous state, is crucial for a successful bioremediation project. Furthermore, the two major approaches to enhance bioremediation are biostimulation and bioaugmentation provided that environmental factors, which determine the success of bioremediation, are maintained at optimal range. This review provides more insight into the two major bioremediation techniques, their principles, advantages, limitations and prospects.

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Bioremediation techniques–classification based on site of application: principles, advantages, limitations and prospects

Microbial fuel cells (MFCs) have been conceived and intensively studied as a promising technology to achieve sustainable wastewater treatment. However, doubts and debates arose in recent years regarding the technical and economic viability of this technology on a larger scale and in a real-world applications. Hence, it is time to think about and examine how to recalibrate this technology's role in a future paradigm of sustainable wastewater treatment. In the past years, many good ideas/approaches have been proposed and investigated for MFC application, but information is scattered. Various review papers were published on MFC configuration, substrates, electrode materials, separators and microbiology but there is lack of critical thinking and systematic analysis of MFC application niche in wastewater treatment. To systematically formulate a strategy of (potentially) practical MFC application and provide information to guide MFC development, this perspective has critically examined and discussed the problems and challenges for developing MFC technology, and identified a possible application niche whereby MFCs can be rationally incorporated into the treatment process. We propose integration of MFCs with other treatment technologies to form an MFC-centered treatment scheme based on thoroughly analyzing the challenges and opportunities, and discuss future efforts to be made for realizing sustainable wastewater treatment.

/pdf/towards-sustainable-wastewater-treatment-by-using-microbial-41sy9mivel.pdf

Towards sustainable wastewater treatment by using microbial fuel cells-centered technologies

A review on dark fermentative biohydrogen production from organic biomass: Process parameters and use of by-products

Continuous dark fermentative hydrogen production by mesophilic microflora: principles and progress

In view of the worldwide economic and environmental issues associated with the extensive use of petro-chemicals, there has been increasing research interest during the past decade in the value of residual biomass. Because of its renewable nature and abundant availability, residual biomass has attracted considerable attention as an alternate feedstock and potential energy source. To expand the range of natural bio-resources, significant progress related to the lignocellulose bio-technology has been achieved, and researchers have been re-directing their interests to biomass-based fuels, ligninolytic enzymes, chemicals, and biocompatible materials, which can be obtained from a variety of lignocellulosic waste materials. This review article focuses on the potential applications of lignocellulosic materials in biotechnology, including the production of bio-fuels, enzymes, chemicals, the pulp and paper, animal feed, and composites.

https://ojs.cnr.ncsu.edu/index.php/BioRes/article/download/BioRes_08_2_3157_Iqbal_Review_Valorization_Lignocellulosic_Materials/2122

Advances in the Valorization of Lignocellulosic Materials by Biotechnology: An Overview

The effect of substrate concentration (sucrose) on the stability and yield of a continuous fermentative process producing hydrogen was studied. High substrate concentrations are attractive from an energy standpoint as they would minimise the energy required for heating. The reactor was a CSTR; temperature was maintained at 35°C; pH was controlled between 5.2 and 5.3, and the hydraulic retention time (HRT) was 12 h. Online measurements were taken for ORP, pH, temperature, %CO2, gas output and %H2, and data logged using a MatLAB® data acquisition toolbox. Steady-state operation was obtained at 10, 20 and 40 g/L of sucrose in the influent, but a subsequent step change to 50 g/L was unsustainable. The hydrogen content ranged between 50% and 60%. The yield of hydrogen decreased as the substrate concentration increased from 1.7 ± 0.2 mol/mol hexose added at 10 g/L, to 0.8 ± 0.1 mol/mol at 50 g/L. Sparging with nitrogen improved the hydrogen yield by at least 35% at 40 g/L and at least 33% at 50 g/L sucrose. Sparging also enabled steady-state operation at 50 g/L sucrose. Addition of an extra 4 g/L of n-butyric acid to the reactor operating at 40 g/L sucrose increased the butyrate concentration from 9,830 to 18,900 mg/L, immediately stopping gas production and initiating the production of propionate, whilst the addition of 2 g/L taking the butyrate concentration to 12,200 mg/L did not do so. It was shown that operation at 50 g/L sucrose in a CSTR in butyrate fermentation is possible. © 2005 Wiley Periodicals, Inc.

Influence of substrate concentration on the stability and yield of continuous biohydrogen production.

The effect of salinity, redox mediators and temperature on anaerobic biodegradation of petroleum hydrocarbons in microbial fuel cells

Complete degradation of the azo dye Acid Orange-7 and bioelectricity generation in an integrated microbial fuel cell, aerobic two-stage bioreactor system in continuous flow mode at ambient temperature.

Godfrey Kyazze

Papers

Continuous dark fermentative hydrogen production by mesophilic microflora: principles and progress

Advances in the Valorization of Lignocellulosic Materials by Biotechnology: An Overview

Influence of substrate concentration on the stability and yield of continuous biohydrogen production.

The effect of salinity, redox mediators and temperature on anaerobic biodegradation of petroleum hydrocarbons in microbial fuel cells

Complete degradation of the azo dye Acid Orange-7 and bioelectricity generation in an integrated microbial fuel cell, aerobic two-stage bioreactor system in continuous flow mode at ambient temperature.