Development of a Low-cost Biogas Monitoring Sensor

This thesis addresses the lack of affordable, accurate flow sensors for monitoring small-scale biogas digesters, a gap that limits digital monitoring, reporting, and verification (dMRV) needed to credibly quantify carbon offsets from biogas-based cooking. The work evaluates candidate flow-measurement technologies and develops a low-cost prototype sensor based on thermal anemometry, incorporating multiple temperature-controlled thermistors to compensate for variations in gas temperature and composition. The sensor was calibrated and tested across a flow range of 0 to 12.5 ln/min and methane concentrations of 50 to 80%. With a production cost of about 45 CHF, the prototype achieved a maximum relative error of 6% for flow rate and 8% for methane composition, comparable to existing commercial low-cost sensors.