Measurements of Flammable Gas Concentration in Landfill Areas with a Low-Cost Sensor

Global warming, as the result of the negative impact of humans on climate change, has been observed based on various data sources. Various measures have aimed to reduce anthropogenic factors, and also to lower carbon dioxide (CO2) and methane CH4 emissions. One of the main contributors to anthropogenic factors is organic waste in municipal solid waste landfills. There are many landfills where cost-effective rapid technologies for the identification and quantification of CH4 emission sites are not applied. There is still a need for the development of accessible and cost-effective methods that react in a real-time manner for the rapid detection and monitoring of methane emissions. This paper’s main goal is to create a prototype sensor suitable for operational measurement of the gas value, suitable for integration into geodetic equipment or an unmanned aerial vehicle system. A sensor system (device) was developed, which consisted of three semiconductor sensors—MQ2, MQ4, and MQ135—which aimed to capture flammable gases (CO2, CH4, O2 purity) and to evaluate the averages of the measured values from the components mounted on the board—the semiconductor sensors. The sensors were calibrated in a laboratory and tested in a closed landfill. The measurement data consisted of the read resistances (analog signal) from the MQ2, MQ4, and MQ135 sensors, and the relative humidity and the temperature (digital signal) of the DHT2 sensor with a timestamp calculated by the RTC module. The use of the method was confirmed because the sensors reacted as expected when placed in the vicinity of the gas collection well. Furthermore, the sensor will be tested and improved for field work in landfill sites.

Perspectives for usage of adsorption semiconductor sensors based on Pd/SnO2 in environmental monitoring of carbon monoxide and methane emission

Nanosized semiconductor sensor materials based on SnO2 with different palladium contents were obtained via zol-gel technology with the use of ethylene glycol and hydrate of tin (VI) chloride as precursors. Morphology and phase composition of nanosized sensor materials were studied by X-ray diffraction and TEM methods. Catalytic activities of the Pd/SnO2 nanomaterials in the reaction of H2 and CO oxidation were investigated. Adsorption semiconductor sensors based on Pd/SnO2 nanomaterials were made by their calcination up to 620 0C in air and the sensors were found to be highly sensitive to presence of CO and CH4 in air ambient. Higher responses to CO of Pd-containing sensors in comparison with their responses to CH4 were confirmed by higher reaction activity of CO in catalytic oxidation reaction. Differences in sensitive properties of the sensors to methane and carbon monoxide were explained by features of the catalytic reactions of methane and carbon monoxide oxidation occurring on surfaces of the gas sensitive layers of the sensors.