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Multiplexed methane measuring machine

15 HEC Engineering project

Biogas is one of the renewable fuels of the future, and is one of the most widely deployed methods for converting biomass (e.g., household waste, straw, manure) into storable energy, electricity, and fertilizer. In order to optimize the biogas process, researchers need to study several aspects of the process, which may require a large number of biogas reactors (glass bottles). These tiny reactors (often 300 ml or up to a liter) produce small amounts of biogas every day. The gas contains methane, which is the energy bearing component of the gas. In order to evaluate how much energy is produced, a researcher typically measures the gas pressure and methane content, and then uses the ideal gas equation to arrive at a number expressed in ml CH4/g biomass (or similar). Gas can also be flushed through an alkaline solution, thereby solubilizing CO2, and then be assumed to have a methane content of 100%.


This project concerns constructing a machine that automatically measures methane from several reactors. It can be built using readily available and cheap components, such as the BMP180 pressure sensor and an appropriate MQ gas sensor, and 3D printed parts where appropriate. The system should be able to monitor several reactors and record the pressure and methane content, preferably multiple times per day. After each reading, the excess pressure is released in order to avoid overpressure in the bottles. The project likely requires the use of a motorized rotary selector valve to connect the reactors to the measurement device. It may be constructed using a Raspberry Pi or an Arduino, and must be capable of outputting its results in a usable format such as CSV. Pressurized gas may be used to evacuate the measuring chamber between readings. It must also be able to calibrate the sensors of the system to ensure accurate readings over time.



  • Jonas Ohlsson, PhD student, Dept. of Mol Sci, SLU. e-mail: jonas.ohlsson (at)​​

  • Simon Isaksson, Research Assistant at the Dept. of Mol Sci, SLU.  e-mail: simon.isaksson (at)

  • Alyona Minina, Ass. Prof.,  Dept. of Mol Sci, SLU. e-mail: alena.minina (at)

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