## 4 Conclusions  
Upgrading the pilot anaerobic bioreactor for biogas production into an IoT device yielded satisfactory monitoring results of the critical parameters. The system effectively tracked biogas production, CH\({}_{4}\) content, pH, and temperature, with minimal variance compared to analytical methods. Further research is recommended to improve ammonia ion measurement using ISE electrodes in AD samples. Nevertheless, this low-cost monitoring system can be adapted to existing bioreactors with minor modifications for electrode integration. Efficient and accurate data recording and storage, which enable easier data processing, represent key advantages of IoT-based systems and make them a valuable addition to anaerobic bioreactors. Overall, this study contributes to the growing role of IoT technologies in addressing global challenges related to sustainable waste management and energy production. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app15010034/s1](https://www.mdpi.com/article/10.3390/app15010034/s1)]([https://www.mdpi.com/article/10.3390/app15010034/s1](https://www.mdpi.com/article/10.3390/app15010034/s1)), Figure S1. Photo images of the anaerobic bioreactor and the IoT devices. a. General view of the reactor and IoT devices, b. Filling of the reactor and view of the stainless-steel helix heat exchanger, c. Measurement cell and ammonium electrode during measurement, d. IoT device of ESP32 for volumetric gas measurements of biogas and its methane content showing real time values, e. Close view of the 2\({}^{\prime\prime}\) display of the IoT device for sensors logging showing real time values, and f. General view of the IoT device for sensors logging and Greisinger GPHU 014 MP-BNC transducer for pH, showing real time values. Figure S2. Measurements from the GPHU 014 MP-BNC transducer connected with Gravity: I2C Digital Wattmeter converters for the creation of the final equation of pH used by ESP32. Figure S3. Measurements for ammonium equation creation by pH/OPR Adapter 1130 which provided analog voltage output and connected to the adapter ADS1115 16-Bit ADC over I2C to ESP32. Solutions with different concentrations were made by deionized water and appropriate addition of NH4 Cl, except for 100 ppm and 1000 ppm standards. Figure S4. Measurements for second ammonium equation creation by pH/OPR Adapter 1130 which provided analog voltage output and connected to the adapter ADS1115 16-Bit ADC over I2C to ESP32. Solutions with different concentrations were made by known concentration sample from the bioreactor and appropriate addition of NH4 Cl. Figure S5. Circuit diagram showing the connections between different parts of the gas monitoring system based on the ESP-32 microcontroller. Figure S6. Circuit diagram showing the connections between different parts of the sensor monitoring system of pH, REDOX, temperature, and ammonium based on the ESP-32 microcontroller. Figure S7. Software flowchart of gas monitoring system. Figure S8. Software flowchart of sensor monitoring system of pH, REDOX, temperature, and ammonium. Table S1. Measurement cell activation schedule of low-cost peristaltic pumps. Conceptualization, S.D.K. ; methodology, S.D.K. ; software, S.D.K. ; validation, S.D.K., M.-A.T., C.A.T., D.S.P. and A.A.L. ; formal analysis, S.D.K. and M.-A.T.; investigation, S.D.K., M.-A.T., C.A.T., D.S.P. and A.A.L. ; resources, S.D.K. and T.A.K. ; data curation, S.D.K. and M.-A.T.; writing--original draft preparation, S.D.K. and M.-A.T.; writing--review and editing, S.D.K. and T.A.K. ; visualization, S.D.K. and M.-A.T.; supervision, S.D.K. and T.A.K. ; project administration, T.A.K. ; funding acquisition, T.A.K. All authors have read and agreed to the published version of the manuscript.