Utilization of Cheese Whey for Energy Generation in Microbial Fuel Cells: Performance Evaluation and Metagenomic Analysis

The dairy industry generates large volumes of whey as a byproduct of cheese production, with a high organic load. Its untreated discharge contaminates water bodies, reduces dissolved oxygen, and damages aquatic ecosystems. In Peru, especially in the rural areas of the Andes, thousands of tons of industrial dairy waste are produced annually, representing an environmental and economic challenge. The lack of sustainable technologies for its management drives the need for innovative solutions, such as microbial fuel cells (MFCs), which combine waste treatment with renewable energy generation. This research uses MFC technology with whey as a substrate to observe its potential to generate electrical energy and treat contaminants. Three liters of whey from a dairy company in Trujillo, Peru, were used and stored at 10 °C. Each MFC contained 800 mL of whey and employed activated carbon as the anode and zinc as the cathode. A maximum voltage of 0.867 ± 0.059 V was reached, with a maximum current of 4.114 ± 0.239 mA recorded on the 11th day. The maximum power density was 1.585 ± 0.061 mW/cm², with a current density of 4.448 A/cm², and the internal resistance of the MFCs was 16.847 ± 0.911 Ω. The initial pH of the whey was approximately 3.0, increasing to 4.135 ± 0.264 on the 11th day, and the electrical conductivity increased from 19.101 ± 1.025 mS/cm on the first day to 170.062 ± 9.511 mS/cm on the 11th day. The oxidation-reduction potential (ORP) increased to 104.287 ± 4.058 mV at the peak of electricity generation (day 11). Additionally, a 70% reduction in chemical oxygen demand (COD) was achieved, dropping from 4650.52 ± 10.54 mg/L to 1400.64 ± 23.25 mg/L on the last day. Metagenomic analysis identified two dominant bacterial phyla: <i>Bacteroidota</i> at 48.47% and <i>Proteobacteria</i> at 29.83%. The most abundant families were <i>Bacteroidaceae</i> (38.58%) and <i>Acetobacteraceae</i> (33.39%). The study validates the potential of MFCs to transform whey into an energy resource, aligning with sustainability and circular economy goals, especially in regions with high dairy production, like Peru.