Energy Recovery with Microbial Fuel Cells: Bioremediation and Bioelectricity

Rice mill wastewater management in the era of circular economy

Several nations around the world use rice as their primary food staple because of its tremendous nutritional value. India's expanding population has sparked a proliferation of rice mills as a result of the country's growing rice demand. However, small and medium-scale industries lack adequate facilities for processing effluents and other waste generated. Paddy is typically processed by parboiling, which involves soaking it in water, boiling it with steam, and then drying and milling. Around 1-1.5 L of water is necessary to partially cook 1 kg of unhusked rice, with approximately half of this water being discharged as effluent. Disposal of rice mill effluent (RME) in water bodies or on the land causes severe damage to soil and water. An inclusive examination of diverse approaches for the treatment and stabilization of partially cooked rice milling effluents is provided. Moreover, the document provides a concise overview of contemporary and environmentally friendly technologies for treating RME. Adsorption, electrocoagulation, chemical coagulation, and bioremediation using microbes, plants, and microalgae are all included in these methods. This manuscript discusses the concept of a circular economy, which is focused on enhancing environmental sustainability through the recycling and repurposing of generated waste into raw materials for the creation of new products. In addition, this review aims to focus on the impact of RME on soils and water species and the status of sustainable management at the point of circular economy with RME bioenergy production (bioelectricity, biomethane, and bio-hydrogen).

Generation of green electricity from sludge using photo-stimulated bacterial consortium as a sustainable technology

Microbial fuel cell (MFC) is a bio-electrical energy generator that uses respiring microbes to transform organic matter present in sludge into electrical energy. The primary goal of this work was to introduce a new approach to the green electricity generation technology. In this context a total of 6 bacterial isolates were recovered from sludge samples collected from El-Sheikh Zayed water purification plant, Egypt, and screened for their electrogenic potential. The most promising isolates were identified according to 16S rRNA sequencing as Escherichia coli and Enterobacter cloacae, promising results were achieved on using them in consortium at optimized values of pH (7.5), temperature (30°C) and substrate (glucose/pyruvate 1%). Low level red laser (λ = 632.8nm, 8mW) was utilized to promote the electrogenic efficiency of the bacterial consortium, maximum growth was attained at 210 sec exposure interval. In an application of adding standard inoculum (107 cfu/mL) of the photo-stimulated bacterial consortium to sludge based MFC a significant increase in the output potential difference values were recorded, the electricity generation was maintained by regular supply of external substrate. These results demonstrate the future development of the dual role of MFCs in renewable energy production and sludge recycling.

Optimization of microbial fuel cell process using a novel consortium for aromatic hydrocarbon bioremediation and bioelectricity generation

Microbial Fuel Cell (MFC) is an innovative bio-electrochemical approach which converts biochemical energy inherent in wastewater into electrical energy, thus contributing to circular economy. Five electrogenic bacteria, Kocuria rosea (GTPAS76), two strains of Bacillus circulans (GTPO28 and GTPAS54), and two strains of Corynebacterium vitaeruminis (GTPO38 and GTPO42) were isolated from a common effluent treatment plant (CETP) and were used individually as well as in consortium form to run double chambered "H" type microbial fuel cell. Individually they could produce voltage in the range of 0.4-0.7 V in the MFC systems. Consortium developed using GTPO28, GTPO38, GTPAS54 and GTPAS76 were capable of producing voltage output of 0.8 V with 81.81 % and 64 % COD and BOD reduction, respectively. The EPS production capacity and electricity generation by the isolated bacteria correlated significantly (r = 0.72). Various parameters like, effect of preformed biofilm, length of salt bridge and its reuse, aeration, substrate concentration and external resistance were studied in detail. The study emphasizes on improving the commercialization aspect of MFC with repeated use of salt bridge and improving wastewater treatment potential after optimization of MFC system. Polarization curve and power density trends were studied in optimized MFC. A maximum power density and current density achieved were 18.15 mW/m² and 370.37 mA/m², respectively using 5 mM sodium benzoate. This study reports the use of sodium benzoate as a substrate along with reusing of the salt bridge in MFC study with promising results for BOD and COD reduction, proving it to be futuristic technology for bio-based circular ecosystem development.

Indirect Carbon Emissions and Energy Consumption Model for Electric Vehicles: Indian Scenario

The environment-friendly nature of E-vehicles (electric vehicles) coupled with higher energy efficiency has increased their popularity in the automotive industry. A detailed study has been conducted in this article to evaluate the role of the energy mix for electricity generation at the charging locations in secondary C emissions from E-vehicles. The E-vehicle market is booming in India. Evaluation of indirect C emissions was conducted for 3 energy mix scenarios in India, and the results showed that in the present energy mix scenario, E-vehicle emissions will be more than that of conventional-fuel-based vehicles. An energy consumption model for the E-vehicle was also developed in this article using MATLAB Simulink, by considering road slope and driving conditions as input parameters. The developed model was tested for 3 driving conditions, namely (i) Flat road at a constant speed, (ii) Extra Urban Driving Cycle (EUDC), and (iii) Real-time driving condition, to estimate the relation between the energy consumption pattern and the driving range with road slope. Simulation results showed variation in the driving range of the E-vehicles regarding input parameters like road slope and vehicle speed. Therefore, this model could serve as an effective tool for establishing charging stations at strategic locations. Integr Environ Assess Manag 2020;16:998-1007. © 2020 SETAC.