Methane is a major greenhouse gas and a precursor of tropospheric ozone, and most
of its sources are linked to anthropogenic activities. The sources of methane are well known and
its monitoring generally involves the use of expensive gas analyzers with high operating costs.
Many studies have investigated the use of low-cost gas sensors as an alternative for measuring
methane concentrations; however, it is still an area that needs further development to ensure reliable
measurements. In this work a low-cost platform for measuring methane within a low concentration
range was developed and used in two distinct environments to continuously assess and improve its
performance. The methane sensor was the Figaro TGS2600, a metal oxide semiconductor (MOS) based
on tin dioxide (SnO2). In a first stage, the monitoring platform was applied in a small ruminant barn
after undergoing a multi-point calibration. In a second stage, the system was used in a wastewater
treatment plant together with a multi-gas analyzer (Gasera One Pulse). The calibration of low-cost
sensor was based on the relation of the readings of the two devices. Temperature and relative
humidity were also measured to perform corrections to minimize the effects of these variables on the
sensor signal and an active ventilation system was used to improve the performance of the sensor.
The system proved to be able to measure low methane concentrations following reliable spatial and
temporal patterns in both places. A very similar behavior between both measuring systems was
also well noticeable at WWTP. In general, the low-cost system presented good performance under
several environmental conditions, showing itself to be a good alternative, at least as a screening
monitoring system.
The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and
FEDER under Programme PT2020 for financial support to CIMO (UIDB/00690/2020) and CeDRI
(UIDB/5757/2020).
