Evaluation of microbial fuel cell performance utilizing sequential batch feeding of different substrates

Conversion of lignocellulosic biomass: Production of bioethanol and bioelectricity using wheat straw hydrolysate in electrochemical bioreactor

The present study evaluated efficiency of wheat straw (WS) hydrolysate obtained through fungal pre-treatment to produce ethanol and electricity in an electrochemical bioreactor. Three white rot fungi Phanerochaete chrysosporium, Phlebia floridensis and Phlebia brevispora were used to degrade WS for hydrolysate preparation, Lignocellulolytic enzyme production was also monitored during the pretreatment. Yeast Pichia fermentans was allowed to ferment all three hydrolysates up to 12 days. The yeast showed maximum electrochemical response as open circuit voltage (0.672 V), current density 542.42 mA m^-2, and power density of 65.09 mW m^-2 on 12th day in the hydrolysate prepared using Phlebia floridensis. Maximum ethanol production of 9.2% (w/v) was achieved on 7th day with a fermentation efficiency of about 62.1%. Further, the coulombic efficiency improved from 0.06 to 1.46% during 12 days of the experiment. Thus, the results indicated towards the possible conversion of lignocellulosic biomass into bioethanol along with bioelectricity generation.

Modelling of self-sustainable microbial fuel cell type oil sensors based on restricted oxygen transfer and two-population competition

Oil leaks during oil industrial chain pose threats to the ecosystem. The microbial fuel cell-type oil sensor has been developed for early warning of such issues. Oil contacting with the sensor restricts oxygen availability and triggers correlative signal anomaly which serves as indicative of the oil presence. To extend its application for the real world, modelling of the sensor is required to pre-describe the signal behavior under unknown conditions. Therefore, by integrating Butler-Volmer, restricted oxygen transfer (ROT) and Monod equations, a dynamic ROT-MFC model with sufficient substrate precondition was developed. The ROT-MFC model was trained on the experimental single-oil-shock test (R 2 = 0.996) and validated by the experimental sequential-shocktest (R 2 = 0.998). Numerical analysis of the trained ROT-MFC model indicates that the single-shock detection has higher sensitivity (≥40.6 mV/detection) and the sequential-shocks detection spends a shorter response time (≤2.2 h). Besides, the sequential-shocks detection with proper strategy is more applicable due to flexible options on detection limit and working range. The model was further evolved into the TPC-ROT-MFC model by introducing a two-population competition (TPC) theory to describe performance under limited substrate conditions. Results indicate a critical substrate concentration range (42.1 to 62.8 mg-COD/L) for dividing baseline steadiness, and that the impact of substrate concentration on anodic charge transfer coefficient soars when the substrate concentration lessens furtherly. This sensor model is relatively easy to implement and may enhance practical use for design and operation.

Bioenergy Potential of Albumin, Acetic Acid, Sucrose, and Blood in Microbial Fuel Cells Treating Synthetic Wastewater

Microbial fuel cells (MFCs) are a recent biotechnology that can simultaneously produce electricity and treat wastewater. As the nature of industrial wastewater is very complex, and it may contain a variety of substrates—such as carbohydrates, proteins, lipids, etc.—previous investigations dealt with treatment of individual pollutants in MFCs; the potential of acetic acid, sucrose, albumin, blood, and their mixture has rarely been reported. Hence, the current investigation explored the contribution of each substrate, both separately and in mixture. The voltage generation potential, current, and power density of five different substrates—namely, acetic acid, sucrose, albumin, blood, and a mixture of all of the substrates—was tested in a dual-chambered, anaerobic MFC operated at 35 °C. The reaction time of the anaerobic batch mode MFC was 24 h, and each substrate was treated for 7 runs under the same conditions. The dual-chambered MFC consisted of anode and cathode chambers; the anode chamber contained the biocatalyst (sludge), while the cathode chamber contained the oxidizing material (KMnO4). The maximum voltage of 769 mV was generated by acetic acid, while its corresponding values of current and power density were 7.69 mA and 347.85 mW, respectively. Similarly, being a simple and readily oxidizable substrate, acetic acid exhibited the highest COD removal efficiency (85%) and highest Coulombic efficiency (72%) per run. The anode accepted the highest number of electrons (0.078 mmol/L) when acetic acid was used as a substrate. The voltage, current, and power density generated were found to be directly proportional to COD concentration. The least voltage (61 mV), current (0.61 mA), and power density (2.18 mW) were observed when blood was treated in the MFC. Further research should be focused on testing the interaction of two or more substrates simultaneously in the MFC.

Bioelectrochemical treatment of real-field bagasse-based paper mill wastewater in dual-chambered microbial fuel cell

The present study is aimed at analysing the feasibility of bioelectrochemical treatment of bagasse-based paper mill wastewater. Bioelectrochemical treatment was carried out in dual-chambered microbial fuel cell with plain graphite plates as electrodes. Wastewater from sugarcane bagasse storage and washing units of paper mill was used as anolyte. High power density and current density of 53 mW m^-2 and 173 mA m^-2 at 470 Ω, respectively, could be produced with wastewater treatment efficiency of 85% and coulumbic efficiency of 6%. Whereas, wastewater from pulping and bleaching units of bagasse-based paper mill was not suitable for bioelectrochemical treatment, yielding low power density and current density of 4 mW m^-2 and 16 mA m^-2 respectively at 10,000 Ω. Later, treating blended wastewater containing bagasse wash water and pulping wastewater in the ratio of 9:1 v/v generated higher power density and current density of 73 mW m^-2/202 mA m^-2, respectively, at 470 Ω, with wastewater treatment efficiency and coulumbic efficiency of 82% and 18%, respectively. Lignin and its derivatives present in pulping wastewater mediated electron transfer leading to high power density. Further, compounds in pulping wastewater were also toxic to methanogens growth in anode chamber of MFC, resulting in improved coulumbic efficiency of the blended wastewater treatment.