Embracing the future of circular bio-enabled economy: unveiling the prospects of microbial fuel cells in achieving true sustainable energy

Voltage recovery from frozen microbial fuel cells in the laboratory and outdoor field reactors

Extreme temperature variations are a problem that must be faced in the practical application of microbial fuel cells (MFCs), but MFCs are not extensively described for low and even freezing temperatures. This study assessed the effect of low-temperature shock on the power generation performance and microbial community structure of MFCs. Two scales of MFCs, the small (mL-MFC) and the large (L-MFC), were constructed in the laboratory and their performance was evaluated before and after freezing at -18 °C. The experimental results demonstrate that both MFCs were capable of rapidly restoring their voltage to the previous level after thawing. For the mL-MFC (rGO/Ag), the power density recovered from 194.30 ± 10.84 mW/m2 to 195.57 ± 4.02 mW/m2 after thawing. For L-MFC (carbon felt electrodes), the power density increased significantly from the initial 1.79 mW/m2 to 173.90 mW/m2 after thawing, but the performance degradation problem after reactor amplification still needs to be solved. The sediment microbial fuel cell (SMFC) was successfully constructed and operated in a natural outdoor environment to maintain high voltage output after the period of frost. Microbial analysis indicated after the frost period, psychrotolerant microorganisms enriched on the anode, such as Flavobacterium and Psychrobacter, while the relative abundance of anaerobic methanogenic bacterium decreased. Overall, freeze-thaw operations had a non-negative impact on the performance of MFCs and provided some references for their practical applications.

Effect of design parameters in nanocatalyst synthesis on pyrolysis for producing diesel-like fuel from waste lubricating oil

Converting waste lubricating oil into diesel-like liquid fuels using pyrolysis presents a dual solution, addressing environmental pollution while offering a viable response to the fossil energy crisis. However, achieving high-quality fuel with a substantial yield necessitates the utilization of highly active and cost-effective catalysts. We report the development of Fe-Ni nanocatalysts, synthesized using a green approach and supported on TiO2, as a promising strategy for converting waste lubricating oil into premium-grade diesel-like fuel. To ensure efficient and effective pyrolysis processes, tailoring the synthesis parameters of these nanocatalysts is indispensable. In this study, we investigate the effect of design parameters on nanocatalyst synthesis, such as the concentrations of pre-catalysts and reducing agents, reducing time, and the amount of support material, and evaluate their impact on the quality and quantity of pyrolysis products. Through optimization of the synthesis process, a high quality diesel-like fuel with a product yield of about 54% at a mild reaction temperature of 400 °C was obtained. This study highlights the critical role of nanocatalysis in addressing persistent environmental and energy challenges while showcasing the potential of green nanocatalysts in sustainable waste-to-energy conversion processes.

A review on recent environmental electrochemistry approaches for the consolidation of a circular economy model

Availability of raw materials in the chemical industry is related to the selection of the chemical processes in which they are used as well as to the efficiency, cost, and eventual evolution to more competitive dynamics of transformation technologies. In general terms however, any chemically transforming technology starts with the extraction, purification, design, manufacture, use, and disposal of materials. It is important to create a new paradigm towards green chemistry, sustainability, and circular economy in the chemical sciences that help to better employ, reuse, and recycle the materials used in every aspect of modern life. Electrochemistry is a growing field of knowledge that can help with these issues to reduce solid waste and the impact of chemical processes on the environment. Several electrochemical studies in the last decades have benefited the recovery of important chemical compounds and elements through electrodeposition, electrowinning, electrocoagulation, electrodialysis, and other processes. The use of living organisms and microorganisms using an electrochemical perspective (known as bioelectrochemistry), is also calling attention to "mining", through plants and microorganisms, essential chemical elements. New process design or the optimization of the current technologies is a major necessity to enhance production and minimize the use of raw materials along with less generation of wastes and secondary by-products. In this context, this contribution aims to show an up-to-date scenario of both environmental electrochemical and bioelectrochemical processes for the extraction, use, recovery and recycling of materials in a circular economy model.