Title : Monitoring by automation of methane gas with use of anaerobic biodigesters and arduino uno plate
Anaerobic digestion is a technology that provides treatment and recycling of waste, adding economic value with the production of biogas and biofertilizer. However, to determine the methane concentration require high sample feeds and have high added value. The objective of this experiment was to evaluate the performance of the automation of the measurement of methane gas present in the biogas from the anaerobic digestion of cattle manure through the Arduino microcontroller. The proportions evaluated in this experiment were 100:0, 75:25, 50:50 and 25:75 in the Bovine Manure:Water (BM:W) ratio. The physicochemical characterization was carried out in the substrate (zero day of anaerobic digestion) and digestate (145th days of anaerobic digestion). The use of the Tracker® software as a Digital Method (DM) to determine the vertical displacement of the anaerobic digester was evaluated. The comparison with Analog Method (AM) was carried out as a preliminary test to analyze the possibility of adopting the Tracker® software for the analysis. The Biogas Analysis Module (BAM) was structured to monitor methane gas with the MQ-4 sensor using the Arduino Uno board. Module validation was performed by Alfakit®. There was an increase in moisture, pH and ST reduction, but the average values were in accordance with the ranges of values considered ideal. The initial values of DM and AM at zero time of anaerobic digestion showed no difference between the methods. However, at the end of the anaerobic digestion, there were differences in the average length found between AM (14.90 cm) and DM (15.22 cm) and a standard error of 2.15%. The biogas production potential for 100:0, 75:25, 50:50 and 25:75 BM:W was, respectively, 1.41; 1.46; 1.45 and 1.51 L kg-1 for the 56th day and 1.37; 1.61; 1.31 and 1.11 L kg-1 for 75:25, 100:0, 50:50 and 25:75 BM:W on the 105th day. With the elaboration of the BAM, the GERAR Code – Methane was suitable for the MQ-4 sensor reading to be targeted for methane detection.
Methane concentration in the biogas in descending order detected by the BAM was, respectively, 72.6; 72.2; 69.6 and 67.7% for 100:0, 75:25, 50:50 and 25:75 BM:W on day 56 and 40.1; 38.1; 36.8 and 34.5% for 75:25, 100:0, 50:50 and 25:75 DE:A on the 105th day. By the validation method with Alfakit®, the concentration of methane in the biogas in descending order detected by the BAM was, respectively, 70; 70; 40 and 40% for 100:0, 75:25, 50:50 and 25:75 BM:W on day 56 and 55; 35; 30 and 20% for 100:0, 75:25, 50:50 and 25:75 DE:A on the 105th day. On day zero of anaerobic digestion methane detection was null in both methods. It is concluded that the bovine manure used presented ideal physicochemical characteristics for the production of biogas. The Tracker® software is a good option to measure the displacement of the gasometer, as the DM obtained more accurate values. The GERAR Code – Methane and the BAM obtained adequate functioning, as it allowed the MQ-4 sensor to perform the stipulated functions and to quantify the methane concentration.