From Waste to Resource: Valorization of Carambola ( Averrhoa carambola ) Residues in Sustainable Bioelectrochemical Technologies

Jonathan Rojas-Flores (), Renny Nazario-Naveda, Santiago M. Benites, Daniel Delfin-Narciso, Moisés Gallazzo Cardenas and Luis Angelats Silva
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Jonathan Rojas-Flores: Facultad de Ingeniería y Arquitectura, Universidad Autónoma del Perú, Lima 15831, Peru
Renny Nazario-Naveda: Facultad de Ingeniería y Arquitectura, Universidad Autónoma del Perú, Lima 15831, Peru
Santiago M. Benites: Facultad de Ingeniería y Arquitectura, Universidad Autónoma del Perú, Lima 15831, Peru
Daniel Delfin-Narciso: Grupo de Investigación en Ciencias Aplicadas y Nuevas Tecnologías, Universidad Privada del Norte, Trujillo 13011, Peru
Moisés Gallazzo Cardenas: Departamento de Ciencias, Universidad Tecnológica del Perú, Trujillo 13011, Peru
Luis Angelats Silva: Laboratorio de Investigación Multidisciplinaria (LABINM), Universidad Privada Antenor Orrego, Trujillo 13008, Peru

Sustainability, 2025, vol. 17, issue 18, 1-16

Abstract: The underutilization of fruit waste in agroindustry—particularly star fruit—leads to leachate generation, emissions, and disposal costs, highlighting the need for circular alternatives that treat organic fractions while producing energy. This study evaluated the bioelectrochemical conversion of carambola ( Averrhoa carambola ) residues in single-chamber microbial fuel cells (MFCs). Three 1000 mL reactors were constructed using carbon anodes and zinc cathodes, operated for 35 days with continuous voltage recording and daily monitoring of pH, conductivity, and ORP. Polarization curves were obtained, and FTIR and SEM analyses were conducted to characterize substrate transformation and anode colonization. The anodic biofilm was also profiled using metagenomics. Measurements were performed using calibrated electrodes and a data logger with one minute intervals. The systems exhibited rapid startup and reached peak performance on day 22, with a voltage of 1.352 V, current of 3.489 mA, conductivity of 177.90 mS/cm, ORP of 202.01 mV, and pH of 4.89. The V–I curve indicated an internal resistance of 16.51 Ω, and the maximum power density reached 0.517 mW/cm 2 . FTIR revealed a reduction in bands associated with carbohydrates and proteins, consistent with biodegradation, while SEM confirmed extensive biofilm formation and increased anode surface roughness. Metagenomic analysis showed dominance of Acetobacter (59.35%), with Bacteroides (12.93%) and lactobacilli contributing to fermentative and electrogenic synergies. Finally, the series connection of three MFCs generated 2.71 V, sufficient to power an LED, demonstrating the feasibility of low-power applications and the potential for system scalability.

Keywords: carambola waste; microbial fuel cells; bioelectricity; electrochemical characterization; circular economy (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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