## 1 Introduction  
In recent decades, economic and demographic growth has posed significant challenges for our society, including water and energy scarcity, the generation of large amounts of waste, and environmental degradation [1]. Currently, fossil fuels supply over 80% of the world's energy demand. However, projections indicate that the reliance on fossil sources will decrease to 73% by 2030 and further to 40% by 2050 [2, 3]. Thus, it is important to develop new renewable and carbon-neutral energy sources, based on raw materials such as biomass, wastewater, and even the conversion of CO\({}_{2}\), to obtain chemicals and energy-dense molecules [4, 5]. It is estimated that biomass derived from agro-industrial processes globally accumulates to over 2 trillion tons per year [6]. Additionally, global wastewater generation is estimated at 359.4 billion m\({}^{3}\) per year, with only 188 billion m\({}^{3}\) per year being treated [7]. The combination of energy generation with waste management would be a very convenient option. This is because it would allow us to treat the waste at the same time that the chemical energy contained in it is valorized [8]. Organic wastes, including food waste, municipal, agricultural, and industrial wastewaters, pose challenges in disposal due to conventional energy-intensive processes generating significant sludge [9; 10; 11]. Nowadays, various technologies exist for the valorization of organic wastes, including incineration, pyrolysis, gasification, and anaerobic digestion, each with its own advantages and drawbacks [10; 12]. Conventional wastewater treatment methods, like activated sludge treatment, are energy-intensive (energy requirements of about 0.3-0.6 kWh/m\({}^{3}\)), presenting significant greenhouse gas (GHG) emissions (about 0.9 kg CO\({}_{2}\)/m\({}^{3}\)) [11]. Given current economic and environmental considerations, there is a pressing need for environmentally friendly and energy-efficient processes, especially those that can extract value from organic waste streams [13; 14]. In this sense, novel approaches, like Microbial Fuel Cell (MFC) technology, a bioelectrochemical system (BES), offer potential for electricity recovery from wastewater with significant environmental and economic advantages (the net worth would be $0.10/kg-COD) [15; 16]. The BES is a revolutionary technology that employs exoelectrogenic and/or electrotrophic microorganisms as biocatalysts within an electrochemical circuit to convert organic matter into electrical energy or to convert electrical energy into value-added organic chemicals using other organic molecules as raw materials, including the conversion of CO\({}_{2}\) to produce useful products such as hydrogen, butanol, etc. [17; 18]. Exoelectrogenic microorganisms donate electrons to an anode during anaerobic oxidation of organic substrates, while heterotrophic organisms can consume electrons from a cathode using processes like electrofermentation of organic matter and bioelectrosynthesis using CO\({}_{2}\) reduction [19; 20]. Based on the aforementioned, BESs include MFCs for electricity generation from chemical reactions and microbial electrolysis cells (MECs) for value-added chemical production consuming electricity [21; 22; 23; 24]. They offer additional benefits such as wastewater treatment, nutrient recovery, and removal of recalcitrant compounds [25; 26]. Photosynthetic microorganisms can also be employed in BESs, as electron donors in MFC bio-anodes for electricity production, as a source of oxygen in the cathode of an MFC, replacing external aeration, or as electron acceptors in a biocathode forming biofilms for various biosynthesis reactions [8; 27; 28]. Overall, BESs are able to integrate electricity generation, wastewater treatment, and value-added products' production while reducing costs and generating less sludge compared to conventional methods [29; 30]. In Figure 1, a basic representation of a BES device is presented. Figure 1: Representation of bioelectrochemical systems.