Ademola Adekunle

A microbial fuel cell (MFC) biosensor with an anode as a sensing element is often unreliable at low or significantly fluctuating organic matter concentrations. To remove this limitation, this work demonstrates capillary action-aided carbon source delivery to an anode-sensing MFC biosensor for use in carbon-depleted environments, e.g., potable water. First, different carbon source delivery configurations using several thread types, silk, nylon, cotton, and polyester, are evaluated. Silk thread was determined to be the most suitable material for passive delivery of a 40 g L⁻¹ acetate solution. This carbon source delivery system was then incorporated into the design of an MFC biosensor for real-time detection of toxicity spikes in tap water, providing an organic matter concentration of 56 ± 15 mg L⁻¹. The biosensor was subsequently able to detect spikes of toxicants such as chlorine, formaldehyde, mercury, and cyanobacterial microcystins. The 16S sequencing results demonstrated the proliferation of Desulfatirhabdium (10.7% of the total population), Pelobacter (10.3%), and Geobacter (10.2%) genera. Overall, this work shows that the proposed approach can be used to achieve real-time toxicant detection by MFC biosensors in carbon-depleted environments.

The effective and economical 3D floating air cathodes were fabricated by a simple dipping-drying method with carbon black (CB), ethanol, and PTFE solution. Pristine Type I polyurethane sponge (5 pores/mm) and Pristine Type II polyurethane sponge (3 pores/mm) were used as the support. The deposition of CB on the Pristine Type I and Pristine Type II materials was detected by scanning electron microscopy and Fourier transform infrared spectroscopy. The carbon loss rate test exhibited good CB adhesive stability on both floating air cathodes. Besides, Type I/CB floating air cathode displayed 3.7 times higher tensile strength, 10.58 times higher elongation at break, and 3.3 times lower cost than carbon felt. The electricity production ability of carbon cloth (CC) anode with carbon felt, Type I/CB, and Type II/CB cathode MFCs (CC-CF-MFC, CC-I-MFC, and CC-II-MFC) was evaluated. After 130 days, the CC-I-MFC showed a maximum power density (PD) of 92.58 mW/m³, which was 4.6 times higher than the CC-CF-MFC. Compared with Type II/CB, Type I/CB cathode improved the maximum power density by 160% due to the smaller pores, rougher surface, and higher surface wettability. Further, CC-I-MFC exhibited the best overall oxidation-reduction performance and chemical oxygen demand removal efficiency. Consequently, Type I/CB floating air cathode opens a new opportunity for scaling up simple, inexpensive, and high-performance MFCs for energy production.

Real-time biomonitoring using microbial fuel cell (MFC) based biosensors have been demonstrated in several laboratory studies, but field validation is lacking. This study describes the long-term performance of an MFC based biosensor developed for real-time monitoring of changes in the water quality of a metal-contaminated stream. After a startup in the laboratory, biosensors were deployed in a stream close to an active mining complex in Sudbury, ON, Canada. Three sites within the stream were selected for biosensors installation based on their positions relative to the mining complex discharge points - upstream (lowest heavy metals concentration), midpoint and downstream. The biosensors installed at these sites were able to detect, in real-time, temporal changes in the water quality over a 2-month period. The biosensor response was confirmed by the results of a conventional toxicity assay (48-h acute Daphnia magna) as well as analytical measurements of heavy metals concentration in the stream. We conclude that the biosensor could detect changes in the overall water quality of the stream despite the uncontrolled situations typical for field operations as compared to laboratory conditions. To further explain the results observed during the field test, the rapid Microtox bioassay and D. magna assay were used to investigate the possible contributions of the two dominant mining metals (Nickel and Copper) to water toxicity in the test area.

Elevated concentrations of heavy metals in water caused by mining activities create significant risks to the environment. Traditional biological methods used to assess heavy metal–related toxicity in aquatic environments are lengthy and labor intensive. Real-time biomonitoring approaches eliminate some of these limitations and provide a more accurate indication of toxicity. This study describes the performance of a flow-through and floating design microbial fuel cell (MFC) biosensors for real-time detection of copper (Cu) and other heavy metal–related toxicity in aquatic environments. Several biomonitoring tests were carried out using Cu and mining effluents as toxicants. The biosensors were able to detect, in real-time, Cu-related toxicity at concentrations as low as 35 - 40 μg L⁻¹, as confirmed by a Daphnia assay. A comparison of the floating biosensor’s outputs with Daphnia magna survival rates showed a linear correlation with a coefficient of determination (R²) higher than 0.9. In addition, the flow-through biosensor was shown to be able to detect differences in the quality of two mining effluents with different compositions of heavy metals. Finally, the biosensor's real-time field performance was investigated in two aquatic environments in the Sudbury, Ontario region of Canada.

This study describes a novel approach for real-time energy harvesting and performance diagnostics of a solid anolyte microbial fuel cell (SA-MFC) representing a prototype smart biobattery. The biobattery power output was maximized in real time by combining intermittent power generation with a Perturbation-and-Observation algorithm for maximum power point tracking. The proposed approach was validated by operating the biobattery under a broad range of environmental conditions affecting power production, such as temperature (4–25 °C), NaCl concentration (up to 2 g L⁻¹), and carbon source concentration. Real-time biobattery performance diagnostics was achieved by estimating key internal parameters (resistance, capacitance, open circuit voltage) using an equivalent electrical circuit model. The real time optimization approach ensured maximum power production during 388 days of biobattery operation under varying environmental conditions, thus confirming the feasibility of biobattery application for powering small electronic devices in field applications.

Small millets, a group of highly nutritious food, have taken a back seat in the Indian agriculture landscape in recent years, due to government policies and failings in the value chain. In this commentary, the unusual decline of small millets in comparison to its substitutes, and the repercussions thereof, were first presented as context. Thereafter, based on analysis of data from literature, survey, and stakeholder contributions, a cluster map for the Indian small millets value chain was designed, and its competitive state presented. This information was used to conceptualize an open innovation driven business model, and an ecosystem for the proposed model was discussed. This commentary provides the first cluster map analysis of small millets value chain in India, and a business model-based approach to stimulating its agribusinesses growth through a synthesis of stakeholders’ contributions and market data.