Toward Sustainability: Electrochemical and Spectroscopic Analysis of Microbial Fuel Cells Using Carrot Pulp

Abstract

Limited access to electricity and high levels of CO₂ emissions—over 35 billion metric tons in recent years—highlight the urgent need for sustainable energy solutions, particularly in rural areas dependent on polluting fuels. To address this challenge, three single-chamber microbial fuel cells (MFCs) with carbon anodes and zinc cathodes were designed and operated for 35 days in a closed circuit. Voltage, current, pH, conductivity, ORP, and COD were monitored. FTIR-ATR spectroscopy (range 4000–400 cm⁻¹) was applied to identify structural changes, and polarization curves were constructed to estimate internal resistance. The main FTIR peaks were observed at 1027, 1636, 3237, and 3374 cm⁻¹, indicating the degradation of polysaccharides and hydroxyl groups. The maximum voltage reached was 0.961 ± 0.025 V, and the peak current was 3.052 ± 0.084 mA on day 16, coinciding with an optimal pH of 4.977 ± 0.058, a conductivity of 194.851 ± 2.847 mS/cm, and an ORP of 126.707 ± 6.958 mV. Connecting the three MFCs in series yielded a total voltage of 2.34 V. Taxonomic analysis of the anodic biofilm revealed a community dominated by Firmicutes (genus Lactobacillus: L. acidophilus, L. brevis, L. casei, L. delbrueckii, L. fermentum, L. helveticus, and L. plantarum), along with Bacteroidota and Proteobacteria (electrogenic bacteria). This microbial synergy enhances electron transfer and validates the use of carrot waste as a renewable source of bioelectricity for low-power applications.

1. Introduction

The global electricity problem is both critical and multifaceted. According to a joint report by the International Energy Agency and the World Bank, 675 million people still lack access to electricity, and 2.3 billion rely on polluting fuels for cooking [1,2]. In addition, in 2022 CO₂ emissions from fossil fuels exceeded 35 billion metric tons, further exacerbating climate change [3]. In response to this crisis, renewable energies have emerged as a key solution: in 2023, more than USD545 billion was invested in solar and wind power, representing 90% of global clean energy investment [4]. This momentum has nearly doubled renewable electricity consumption over the past decade [5]. However, coal and oil still dominate the global energy mix [6]. Transitioning to renewable sources would not only reduce emissions but also improve public health, promote equitable energy access, and strengthen energy security [7].

Agricultural waste is a valuable resource for renewable energy generation, particularly in the form of biomass [8]. Examples include rice straw, sugarcane bagasse, vegetable waste, and coffee husks, which can be converted into biofuels or electricity through combustion or anaerobic digestion [9,10]. In Peru, biomass potential is significant, with projects using such residues to reduce fossil fuel dependence and promote rural development [11]. According to IRENA, bioenergy could supply up to 22% of the world’s energy by 2050, highlighting the strategic role of agricultural residues in the energy transition [12]. Microbial fuel cells (MFCs) are bioelectrochemical devices that convert the chemical energy of organic substrates into electricity via microorganisms [13]. They generate clean energy while treating wastewater and degrading organic matter [14]. An MFC consists of an anode, where microorganisms oxidize the substrate; a cathode, which receives electrons; a membrane separating the chambers; and an external circuit allowing current flow [15]. Although their power output is still limited, MFCs are a promising alternative for sustainable energy, especially in rural or resource-limited areas [16]. Studies have explored agricultural waste potential: MFCs using pineapple pulp achieved ~0.3484 ± 0.003 V, ~27.88 ± 0.23 mA, and a maximum power density of 0.967 ± 0.059 W/cm² [17]. Other substrates, such as avocado waste, performed best at pH5.98 ± 0.16 [18]. MFCs using avocado, tomato, banana, mango, and mixed fruit waste with manure and rumen fluid as microbial sources showed tomato reaching 0.593 V and avocado achieving 63.11 mA/m² current density on day 7 [19].

In Peru, carrot production reached 192,126 tons in 2020, cultivated over 7617 ha with an average yield of 25.2 t/ha [20]. Between 20% and 30% of this becomes waste during harvesting, processing, and marketing—about 38,000 to 57,000 tons annually [21]. This includes peels, pulp, and carrots discarded for aesthetic or physical defects. This crop is primarily grown in the coastal and highland valleys, with notable contributions from regions such as Lima, Arequipa, Junín, Cusco, Áncash, and La Libertad. Its significance lies not only in its nutritional value and consistent market demand, but also in its role as a source of income for thousands of smallholder farmers [22]. However, despite its economic and dietary importance, carrot production faces serious sustainability challenges. One of the most pressing issues is seasonal oversupply, which causes abrupt price fluctuations and undermines farmers’ profitability. In recent harvest cycles, the farmgate price per kilogram has ranged from USD 0.16 to USD 0.32, depending on market saturation [23]. This volatility, coupled with limited access to agricultural technologies, restricts producers’ ability to plan and diversify their crops effectively. Moreover, intensive carrot cultivation is often associated with excessive use of chemical fertilizers and irrigation water, which can degrade soil health and contribute to environmental stress if not properly managed. Many farmers lack their own machinery, forcing them to rent equipment at high operational costs—often exceeding USD 150 per hectare—further reducing profit margins [22]. In response to these challenges, the Ministry of Agrarian Development and Irrigation (MIDAGRI) has promoted agricultural diversification strategies, encouraging crop rotation and the use of native varieties as alternatives to mitigate economic and ecological risks [21,23]. Initiatives have also been launched to improve commercialization channels, optimize resource use, and promote sustainable practices that reduce the environmental footprint of carrot farming. These residues are rich in sugars, hemicellulose, and pectins—ideal compounds for feeding microorganisms in MFCs [20,23]. Using carrot waste in MFCs not only reduces the environmental burden of agro-industrial waste but also generates renewable energy for rural or off-grid areas.

This study aims to evaluate an MFC system that converts carrot waste from Peruvian markets into bioelectricity for low-power applications while contributing to organic matter treatment. Over 35 days, parameters such as pH, voltage, current, ORP, conductivity, and COD will be monitored to assess electrochemical stability and system efficiency. FTIR spectroscopy will be applied to identify structural changes in the substrate, and total internal resistance will be estimated by constructing polarization curves to determine power density. The study proposes a renewable, reproducible energy solution suitable for communities with limited electricity access. The utilization of carrot waste as an energy source represents an innovative and sustainable strategy to address current environmental and energy challenges. In Peru, where carrot production generates tons of organic waste annually, a significant portion of these residues is discarded without treatment, contributing to pollution and resource loss. Transforming this waste into bioenergy aligns directly with the principles of the circular economy by closing the loop between agricultural production and consumption. Moreover, it fosters environmental equity by offering accessible and replicable technological solutions for vulnerable communities. This approach not only mitigates the environmental impact of agro-industrial activities but also creates opportunities for decentralized energy generation, particularly in rural areas with limited access to conventional power grids. In the broader context of global climate crisis and resource scarcity, the use of agro-industrial waste as an alternative fuel is not merely a scientific opportunity—it is an ethical commitment to planetary sustainability and the well-being of future generations. By integrating waste valorization into energy systems, societies can reduce dependence on fossil fuels, lower greenhouse gas emissions, and promote inclusive development through clean and locally sourced energy solutions.

2. Materials and Methods

2.1. Design and Manufacture of the MFCs

This study employed three single-chamber microbial fuel cells (MFCs), each constructed using one-liter Pyrex glass containers as the working volume. The anode consisted of a 3 × 5 cm carbon sheet (Rod Graphite^®, Shenzhen, China), pretreated with 1M nitric acid to increase its active surface area and remove impurities, followed by rinsing with sterile distilled water. The cathode was a zinc plate (Arequipa steel) of the same dimensions, polished with fine sandpaper and disinfected with 70% ethanol. Both electrodes were positioned 4 cm apart and connected via copper wires to an adjustable external resistor of 100 Ω for polarization testing (see Figure 1). This study employed carrot waste (Daucus carota) as the primary substrate, selected from post-harvest residues at an intermediate stage of decomposition. The material was manually collected in the district of Laredo, Trujillo, Peru, under hygienic handling conditions to avoid external contamination. The carrot waste was washed with distilled water and homogenized using an industrial blender (Oster^® model BLSTVB-RV0-000, manufactured in Atlanta, GA, USA), yielding a uniform mixture that served as the organic feedstock for the microbial fuel cells.

2.2. Substrate Preparation

The substrate was prepared from carrot waste, which was washed, chopped, and ground to obtain a homogeneous pulp. This pulp was used directly in the anode chamber, taking advantage of its high carbohydrate and organic acid content as an energy source for electrogenic microorganisms. The MFCs were operated for 35 days in a closed circuit with the cathode exposed to air. An initial 24 h acclimation phase in open circuit mode was established to promote microbial colonization of the anode. During operation, evaporated volume was replenished aseptically without a complete medium replacement.

2.3. Parameter Monitoring and Microorganism Isolation

Monitoring included continuous voltage recording using a data logger (UNI-T^® UT61E, Beijing, China) at one-minute intervals. Current was calculated using Ohm’s law (I = V/R), and polarization curves were acquired with a variable resistor box (Resistor Decade Box, Extech^® RDB10, Pittsburgh, PA, USA). Current and power density were determined based on electrode surface area, and internal resistance was estimated from the slope of the linear region of the V–I curve. To measure voltage and current, a variable resistor (potentiometer) was used as the external load. At each measurement point, the resistance was manually adjusted until a stable maximum voltage was achieved, at which point the corresponding current was simultaneously recorded using a multimeter in a closed-circuit configuration. This procedure enabled the collection of voltage–current pairs under optimized load conditions, without maintaining a constant resistance or current across measurements. The curves shown in Figure 2a,b reflect this variation, illustrating the electrical behavior of the system under different load conditions. Daily measurements of pH, electrical conductivity, and oxidation-reduction potential (ORP) were performed using calibrated electrodes connected to a multiparameter meter (Hanna Instruments^® HI5522, Bucarest, Romania). Chemical oxygen demand (COD) was assessed via closed reflux dichromate digestion at 150 °C for two hours, using Hach^® COD HR kits (Loveland, CO, USA) and a digital reactor block (Hach^® DRB200, Loveland, CO, USA). To characterize changes in the substrate and anodic biofilm, Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) was applied in the 4000–400 cm⁻¹ range using a Bruker^® Alpha II spectrometer (Berlin, Germany).

2.4. Isolation of Microbial Strains from the Anode

At the end of the MFC operational period, electrogenic microorganisms from the anodic biofilm were recovered. Areas of the electrode with visible colonization were selected and swabbed under sterile conditions using sterile cotton swabs (Puritan^® 25-806 1PD, Guilford, ME, USA), ensuring sampling from both the surface and micro-crevices where active communities tend to concentrate. Swabs were immediately transferred to sterile tubes containing saline solution (0.85% NaCl; Merck^® EMSURE^®, Hamburg, Germany) to maintain cell viability during transport. The suspensions were streaked onto selective and differential media: nutrient agar (Oxoid^® CM0001, London, UK) and MacConkey agar (Oxoid^® CM0007, UK) for bacterial isolation, and Sabouraud agar (BD Difco™ 271120, Franklin Lakes, NJ, USA) for fungi and yeasts. Plates were incubated at 30 °C for 24–48 h in a microbiological incubator (Memmert^® IN30, Hamburg, Germany), monitoring the appearance of colonies with distinct morphologies. Each morphotype was subcultured on agar slants to obtain pure cultures. Preliminary characterization included Gram staining (BD BBL™ Gram-stain Kit, Franklin Lakes, NJ, USA) for bacteria and lactophenol cotton blue staining (Sigma-Aldrich^®, Hamburg, Germany) for fungi, followed by microscopic observation using an optical microscope (Leica^® DM500, Hamburg, Germany) to assess cell morphology and reproductive structures.

2.5. Molecular Identification of Electrogenic Strains

Pure strains obtained from the anodic biofilm were sent to a specialized molecular biology laboratory for genetic analysis. Genomic DNA was extracted using commercial kits optimized for bacteria and fungi (Qiagen^® DNeasy Blood & Tissue Kit, Hmaburg, Germany), ensuring high purity and concentration of genetic material. PCR amplification of conserved gene regions was performed using a thermal cycler (Bio-Rad^® T100™, Hercules, CA, USA), targeting the 16S rRNA gene (~1500 bp) for bacteria and the ITS (Internal Transcribed Spacer) region for fungi, to obtain high-resolution taxonomic markers. Amplicons were sequenced using the Sanger method with an ABI Prism^® 3130 Genetic Analyzer (Applied Biosystems^®, Waltham, MA, USA). Sequences were edited and aligned using MEGA X software (Pennsylvania State University, University Park, PA, USA), and compared against the NCBI BLAST database to determine percentage identity and assign taxonomic classification at the genus and species levels.

3. Results and Analysis

Figure 2a shows the voltage performance values of the MFCs fed with carrot waste. On day 1, the initial voltage was 0.075 ± 0.001 V, reflecting a microbial adaptation phase to the substrate. As the microorganisms began degrading the organic compounds in the carrot—rich in sugars, pectins, and hemicelluloses—the voltage increased progressively [21]. The maximum value, 0.961 ± 0.025 V, was reached on day 16, indicating a stage of high efficiency in bioelectrochemical conversion. This peak suggests that the microorganisms had established an active and stable community, optimizing electron transfer to the anode [24]. After day 20, the voltage gradually decreased, reaching 0.533 ± 0.029 V by day 35, possibly due to substrate depletion or the accumulation of by-products that inhibit microbial activity [25]. According to the study by Mulyono et al. (2022), MFCs using mustard, spinach, and kale waste as substrates achieved an average voltage of 0.804 V and a maximum power output of 134 W with spinach waste [26]. Similarly, Ahmad et al. (2024) evaluated microbial fuel cells using vegetable waste as substrate, reaching a maximum voltage of 0.9 V, demonstrating the potential of agricultural residues as an efficient source of bioelectricity for sustainable applications [27]. Figure 2b presents the current output behavior of MFCs fed with carrot waste as the organic substrate. On day1, the initial current was 0.148 ± 0.001 mA, again reflecting a microbial adaptation phase. As the microorganisms metabolized the organic compounds in the carrot waste—such as sugars, pectins, and hemicelluloses—the current increased progressively [22]. The system reached its maximum current output of 3.052 ± 0.084 mA on day16, indicating a stage of high efficiency in electron transfer [25], followed by a gradual decline to 1.974 ± 0.141 mA by day 35, likely due to substrate depletion or inhibitory by-product accumulation [28]. The error bars reflect experimental variability, more pronounced during periods of peak microbial activity [28]. These data demonstrate that carrot waste is a viable substrate for MFCs, offering significant peaks in energy production and high initial performance, although dependent on continuous supply or substrate renewal to sustain generation over time.

Figure 3a shows pH monitoring in MFCs fed with carrot waste, revealing a progressive increase from initially acidic values (~4.1) to near-neutral levels (~5.9), reflecting the progression of microbial activity and the degradation of organic compounds. On day16, a pH of 4.977 ± 0.058 was recorded, considered optimal for the electrochemical performance of the system. This value indicates a favorable condition for electrogenic bacteria, which require a slightly acidic environment to metabolize the sugars and pectins present in carrot waste [29]. pH directly influences electron transfer efficiency and the stability of redox processes within the MFC; excessively low pH can inhibit microbial activity, while excessively high pH can affect conductivity and electrode structure [30]. Thus, day16 represents a key point in system performance, coinciding with the maximum voltage and current values observed. Studies using agricultural residues have reported similar findings, such as an optimal pH of 5.98 ± 0.16 for avocado waste [31], increases from 3.848 to 8.227 ± 0.35 in papaya waste systems, and an optimal pH of 7.85 ± 0.22 in Galactomyces sp. yeast systems [32].

Figure 3b shows the evolution of electrical conductivity (mS/cm) in the MFCs over 35 days. Conductivity increased from 49.307 ± 1.511 mS/cm on day 1 to a peak of 194.851 ± 2.847 mS/cm on day 16, suggesting an active phase of biofilm formation and microbial substrate degradation [25]. It then gradually decreased, stabilizing around 154.216 ± 3.614 mS/cm by day 35, indicating reduced metabolic activity or depletion of easily biodegradable compounds [33]. Error bars (±SD) show controlled variability, supporting system reproducibility. This confirms that carrot waste can create a favorable electrochemical environment in MFCs, with optimal performance between days 10 and 20. Other studies have reported conductivity ranges of 2.0–40.1 mS/cm for waste-derived electrolytes, with higher ionic strength (e.g., hydrolyzed human urine > 50 mS/cm) enhancing power output [34]. Increased salinity from NaCl accumulation has also been shown to raise conductivity and improve electrochemical performance [35].

Figure 3c shows the evolution of oxidation–reduction potential (ORP) in MFCs. The initial ORP of 16.694 ± 1.532 mV reflects a slightly oxidizing environment; this increased to 126.707 ± 6.958 mV on day 16, indicating sustained accumulation of oxidized species generated by microbial activity. This peak reflects maximum oxidation processes linked to the degradation of organic compounds [28]. The slight decline to 83.545 ± 8.694 mV by the final day suggests substrate depletion and possible inhibitory effects of secondary metabolites. The slope analysis from days 0 to16 identifies this as the optimal oxidation period for maintaining favorable redox conditions [36]. In other studies, ORP values have ranged from ~135 mV in early treatment phases to 330–610 mV as the system matured and biofilm developed [37].

Figure 4 shows the FTIR spectrum of carrot waste after operation in microbial fuel cells, revealing four main peaks (1027 cm⁻¹, 1636 cm⁻¹, 3237 cm⁻¹, and 3374 cm⁻¹). The peak at 1027 cm⁻¹ is primarily associated with C–O stretching vibrations from alcohols and polysaccharides. However, in complex carbon-rich substrates such as carrot waste, overlapping contributions from C–C and C–H bonds are likely, as previously reported in heterogeneous organic matrices [38]. The peaks at 3237 cm⁻¹ and 3374 cm⁻¹ indicate the presence of hydroxyl groups (–OH), commonly found in cellulose, hemicellulose, and lignin [39]. The decrease in the intensity of these peaks in the final spectrum suggests a transformation of the organic compounds present in the carrot waste, likely associated with microbial degradation. However, it is acknowledged that ATR-FTIR measurements are semi-quantitative and may be influenced by sample contact and quantity. Therefore, this observation should be interpreted as indicative rather than conclusive. The observed spectral changes, particularly the attenuation of bands associated with C–O, C–H, and C=O functional groups, are consistent with microbial oxidation and breakdown of aliphatic and carboxylic structures [40]. While no evidence of heteroatom doping, cross-linking, or structural disordering was targeted in this study, the degradation pathway appears to involve biochemical transformation of soluble organic matter. Future studies incorporating complementary techniques such as TGA or NMR could help elucidate the molecular mechanisms involved [41].

Figure 5 presents the taxonomic analysis of the MFC anode electrode, revealing a microbial community dominated by genera belonging to the phyla Firmicutes, Bacteroidota, and Proteobacteria, as shown in the circular phylogenetic tree (Figure 5). Within Firmicutes, species of the genus Lactobacillus stand out, including L. acidophilus, L. brevis, L. casei, L. delbrueckii, L. fermentum, L. helveticus, and L. plantarum. These microorganisms are known for their ability to form robust biofilms and for their fermentative metabolism, which supports electron production under anaerobic conditions [42]. The presence of Secundilactobacillus suggests functional diversification within the biofilm, possibly linked to the degradation of complex plant compounds such as those found in carrot waste [43]. Members of Proteobacteria often include electrogenic bacteria such as Geobacter or Shewanella—although not specified in this figure, their presence is common in active anode electrodes [44]. Bacteroidota, although less studied in MFCs, may contribute to the hydrolysis of organic polymers and enhance substrate availability for electrogenic bacteria [44]. This taxonomic diversity indicates a synergistic microbial structure in which fermentative and electrogenic genera coexist to maximize electron transfer to the electrode. Studies have reported that electrode modifications with materials such as polyaniline (PANI), nitrogen-doped carbon nanostructures, reduced graphene oxide (rGO), and carbon nanotubes (CNTs) significantly influence microbial selection [45]. Modified anodes—particularly those using PANI combined with plant-based powders—offer improved biocompatibility and nutrient supply, favoring the colonization of electrogenic bacteria (e.g., Clostridium, Pseudomonas, Enterobacter), even though rGO or CNTs may provide higher conductivity on paper. Such modifications promote the growth of electrochemically active biofilms, thereby enhancing performance in terms of current and voltage output [46].

Figure 6 depicts an experimental process for electrical energy generation using MFCs, framed within the valorization of agro-industrial waste and the pursuit of sustainable energy solutions. The visual diagram is organized in a logical sequence, illustrating the pathway from the raw material (fresh carrots) to the production of bioelectricity. The cables connected to the MFCs indicate electron transfer from the biofilms to a multimeter, where a voltage of 2.34 V is recorded. Three MFCs connected in series demonstrate a strategy to increase the total electrical potential and optimize the system’s energy output. The modular arrangement suggests scalability and ease of monitoring. This visual scheme highlights the sustainability of using agro-industrial waste, transforming them into a renewable, decentralized energy source. It also highlights the versatility of MFCs to adapt to different plant-based substrates. Overall, the diagram conveys an innovative solution for waste management and energy recovery.

The comparative

Table 1. Comparative table of agro-industrial substrates used in MFCs.

Substrate	Pretreatment	Organic Composition	Power Density (mW/m2)	Operational Stability	Remarks
Carrot Pulp [This investigation].	None	Simple sugars + insoluble fiber	Moderate	Stable	Fiber may limit biodegradability; good performance without pretreatment
Lettuce [17]	None	Water + cellulose	Low	Variable	Low energy density; requires load optimization
Banana peel [47]	None	Starch + fiber	Moderate	Stable	Balanced biodegradability and energy availability
Passion fruit Pulp [48]	None	Sugars + organic acids	High	Stable	High microbial activity; efficient bioelectrochemical conversion
Potato peel [49]	None	Starch + phenolic compounds	Moderate	Variable	Pretreatment may enhance degradation and performance
Sugarcane bagasse [50]	Yes (crushed)	Fiber + residual sugars	High	Stable	High energy availability; good performance with minimal processing
Tomato Pulp [51].	None	Sugars + organic acids	Moderate	Stable	Good microbial response; high water content may dilute organic load
Orange peel [52].	None	Sugars + essential oils	Low–Moderate	Variable	Antimicrobial compounds may inhibit electrogenic activity

highlights nine agro-industrial substrates evaluated for their suitability in microbial fuel cells, focusing on organic composition, pretreatment requirements, power output, and operational stability. Substrates rich in simple sugars, such as mango and passion fruit pulp, demonstrated the highest power densities and stable performance. Their rapid fermentability enhances microbial activity, making them ideal candidates for maximizing bioelectrochemical efficiency without additional processing. In contrast, substrates with high fiber or starch content—like carrot pulp, banana peel, and potato peel—showed moderate power output. Although their biodegradability is lower, they offer consistent performance and are well-suited for sustainable applications in low-resource settings. Carrot pulp, in particular, stands out for its ability to generate electricity without pretreatment, reinforcing its practicality in decentralized systems.

Substrates with high water content, such as lettuce and tomato pulp, exhibited lower energy density and variable performance. Their diluted organic load may limit microbial activity unless combined with other substrates or optimized through pretreatment. Orange peel presents a unique challenge due to its antimicrobial compounds, which can inhibit electrogenic bacteria and reduce system efficiency. Sugarcane bagasse, despite requiring minimal crushing, delivered high power density and stable operation, positioning it as a competitive substrate for scalable applications. Overall, the analysis underscores the importance of selecting substrates based not only on energy potential but also on accessibility, degradability, and compatibility with microbial communities. This comparison supports the development of sustainable MFC systems tailored to local waste streams and operational constraints.

4. Conclusions

The conclusions of this study confirmed that carrot waste is a viable and efficient substrate for bioelectricity generation through microbial fuel cells (MFCs). Based on the objectives set, it was demonstrated that the system achieved optimal electrochemical performance between days 10 and 20 of operation, with a maximum voltage of 0.961 ± 0.025 V and a peak current of 3.052 ± 0.084 mA on day 16. These values reflect a phase of high microbial activity and efficient electron transfer, supported by favorable conditions of pH (4.977 ± 0.058), electrical conductivity (194.851 ± 2.847 mS/cm), and redox potential (126.707 ± 6.958 mV). FTIR spectroscopic analysis revealed characteristic peaks at 1027 cm⁻¹ (C–O vibrations from polysaccharides), 1636 cm⁻¹ (presence of carbonyl groups), and broad bands at 3237 and 3374 cm⁻¹ (hydroxyl group stretching), all of which decreased in intensity after the process, indicating significant degradation of the organic compounds present in the waste. This biochemical transformation was key to energy generation. Furthermore, the taxonomic analysis of the anode biofilm showed a diverse microbial community, dominated by fermentative genera such as Lactobacillus and electrogenic genera such as Proteobacteria, suggesting a functional synergy favorable for electricity production. Connecting three MFCs in series yielded a cumulative voltage of 2.34 V, demonstrating the system’s feasibility for low-power applications. Overall, these findings validate the use of agro-industrial waste as a renewable energy source, promoting sustainable solutions for rural communities and contributing to the valorization of organic waste within the framework of the energy transition.

Future work should focus on optimizing MFC design by incorporating advanced electrode materials that enhance electrochemical efficiency and microbial colonization. It is also proposed to assess system scalability through modular prototypes connected in series or parallel, with the aim of powering low-consumption devices in rural areas. Another relevant line of research involves comparing the performance of different local agro-industrial residues, such as potato peels or sugarcane bagasse, to identify blends that enhance electricity generation. Additionally, further study of the anode biofilm is recommended, applying bioaugmentation techniques or synthetic microbial consortia to improve system stability and productivity.