The application of low-cost sensors in estimates of greenhouse gases : A field study at a wastewater treatment plant

Sammanfattning: Anthropogenic activity has caused increased concentrations of greenhouse gases (GHGs) in the atmosphere which has resulted in global warming gaining momentum. GHG emission estimates up to date are insufficient and in order to mitigate GHG emissions of anthropogenic origin fluxes of GHGs need to be mapped. The application of low-cost sensors (LCSs) as an environmental monitoring tool has been seen as a pathway with the ability to provide GHG estimates that can help us to identify sources and sinks. However, questions have been highlighted regarding the accuracy of LCSs in targeting GHGs in comparison to alternative environmental monitoring approaches. A network of LCSs with the ability to target carbon dioxide (CO2) and methane (CH4), among other environmental parameters of interest, were deployed at a wastewater treatment plant (WWTP) in Linköping, Sweden. A cross-checking procedure where LCS data were compared with data from high-precision measuring instruments UltraPortable Greenhouse Gas Analyser (UGGA) and air samples analysed with gas chromatography (GC), enabled evaluation of LCSs as an environmental monitoring tool. Despite uncertainties regarding individual sensors´ behaviour, results from this study show that LCS systems have the capability to bring valuable estimates of GHGs to the environmental monitoring field, although not yet at the precise level of reference equipment. The low cost of the LCS systems studied in this work open a range of possibilities because of their ability to provide large amounts of data on both a spatial and temporal scale that are not attainable for high-precision reference instruments. From the long-term measurements it can be concluded that the CO2 concentrations at the dewatered sludge deposit, and especially inside the screw conveyor building, are higher than global average levels of CO2.