Reducing the burden of food processing washdown wastewaters using microbial fuel cells

Bioelectrochemical systems (BESs) for agro-food waste and wastewater treatment, and sustainable bioenergy-A review

Producing food by farming and subsequent food manufacturing are central to the world's food supply, accounting for more than half of all production. Production is, however, closely related to the creation of large amounts of organic wastes or byproducts (agro-food waste or wastewater) that negatively impact the environment and the climate. Global climate change mitigation is an urgent need that necessitates sustainable development. For that purpose, proper agro-food waste and wastewater management are essential, not only for waste reduction but also for resource optimization. To achieve sustainability in food production, biotechnology is considered as key factor since its continuous development and broad implementation will potentially benefit ecosystems by turning polluting waste into biodegradable materials; this will become more feasible and common as environmentally friendly industrial processes improve. Bioelectrochemical systems are a revitalized, promising biotechnology integrating microorganisms (or enzymes) with multifaceted applications. The technology can efficiently reduce waste and wastewater while recovering energy and chemicals, taking advantage of their biological elements' specific redox processes. In this review, a consolidated description of agro-food waste and wastewater and its remediation possibilities, using different bioelectrochemical-based systems is presented and discussed together with a critical view of the current and future potential applications.

Organic Waste Substrates for Bioenergy Production via Microbial Fuel Cells: A Key Point Review

High-energy consumption globally has raised questions about the low environmentally friendly and high-cost processes used until now for energy production. Microbial fuel cells (MFCs) may support alternative more economically and environmentally favorable ways of bioenergy production based on their advantage of using waste. MFCs work as bio-electrochemical devices that consume organic substrates in order for the electrogenic bacteria and/or enzyme cultures to produce electricity and simultaneously lower the environmental hazardous value of waste such as COD. The utilization of organic waste as fuels in MFCs has opened a new research path for testing a variety of by-products from several industry sectors. This review presents several organic waste substrates that can be employed as fuels in MFCs for bioenergy generation and the effect of their usage on power density, COD (chemical oxygen demand) removal, and Coulombic efficiency enhancement. Moreover, a demonstration and comparison of the different types of mixed waste regarding their efficiency for energy generation via MFCs are presented. Future perspectives for manufacturing and cost analysis plans can support scale-up processes fulfilling waste-treatment efficiency and energy-output densities.

Review on microbial fuel cells applications, developments and costs

The microbial fuel cell (MFC) technology has attracted significant attention in the last years due to its potential to recover energy in a wastewater treatment. The idea of using an MFC in industry is very attractive as the organic wastes can be converted into energy, reducing the waste disposal costs and the energy needs while increasing the company profit. However, taking aside these promising prospects, the attempts to apply MFCs in large-scale have not been succeeded so far since their lower performance and high costs remains challenging. This review intends to present the main applications of the MFC systems and its developments, particularly the advances on configuration and operating conditions. The diagnostic techniques used to evaluate the MFC performance as well as the different modeling approaches are described. Towards the introduction of the MFC in the market, a cost analysis is also included. The development of low-cost materials and more efficient systems, with high higher power outputs and durability, are crucial towards the application of MFCs in industrial/large scale. This work is a helpful tool for discovering new operation and design regimes.

Sequentially recover heavy metals from smelting wastewater using bioelectrochemical system coupled with thermoelectric generators

Smelting wastewater is characterized with high concentration of toxic heavy metals and high acidity, which must be properly treated before discharge. Here, bioelectrochemical system (BES) coupled with thermoelectric generator (TEG) was first demonstrated to simultaneously treat organic wastewater and smelting wastewater by utilizing the simulated waste heat that was abundant in smelting factories. By modulating the input voltage generated from simulated waste heat via TEG to 0, 1.0 and 2.0 V, almost all the Cu²⁺, Cd²⁺ and Co²⁺ in smelting wastewater were sequentially recovered with a respective rate of 121.17, 158.20 and 193.87 mg L^-1 d^-1. Cu²⁺ was bioelectrochemically recovered as Cu⁰. While, Cd²⁺ and Co²⁺ were recovered by electrodeposition as Cd(OH)₂, CdCO₃ or Co(OH)₂ on cathodic surface. High throughput sequencing analysis showed that the microbial community of anodic biofilm was greatly shifted after successive treatment by batch-mode. Desulfovibrio (17.00%), Megasphaera (11.81%), Geobacter (10.36%) and Propionibacterium (8.64%) were predominant genera in anodic biofilm enriched from activated sludge in BES before treatment. After successive treatment by batch-mode, Geobacter (34.76%), Microbacter (8.60%) and Desulfovibrio (5.33%) were shifted as the major genera. Economic analysis revealed that it was feasible to use TEG to substitute electrical grid energy to integrate with BES for wastewater treatment. In addition, literature review indicated that it was not uncommon for the coexistence of waste heat with typical pollutants (e.g. heavy metal ions and various biodegradation-resistant organic wastes) that could be treated by BES in different kinds of factories or geothermal sites. This study provides novel insights to expand the application potentials of BES by integrating with TEG to utilize widespread waste heat.

Storing of exoelectrogenic anolyte for efficient microbial fuel cell recovery

Starting up a microbial fuel cell (MFC) requires often a long-term culture enrichment period, which is a challenge after process upsets. The purpose of this study was to develop low-cost storage for MFC enrichment culture to enable prompt process recovery after upsets. Anolyte of an operating xylose-fed MFC was stored at different temperatures and for different time periods. Storing the anolyte for 1 week or 1 month at +4°C did not significantly affect power production, but the lag time for power production was increased from 2 days to 3 or 5 days, respectively. One month storing at -20°C increased the lag time to 7 days. The average power density in these MFCs varied between 1.2 and 1.7 W/m³. The share of dead cells (measured by live/dead staining) increased with storing time. After 6-month storage, the power production was insignificant. However, xylose removal remained similar in all cultures (99-100%) while volatile fatty acids production varied. The results indicate that fermentative organisms tolerated the long storage better than the exoelectrogens. As storing at +4°C is less energy intensive compared to freezing, anolyte storage at +4°C for a maximum of 1 month is recommended as start-up seed for MFC after process failure to enable efficient process recovery.