Estimating Methane Emission Rate from an Oxidation Lagoon Using Low-Cost Sensor

Abstract

Abstract In Mexico, the second source of methane emissions is anaerobic digestion of waste, then is necessary the development of methane emission measurement methodologies to evaluate the mitigation measures adopted. This work describes a methodology for the estimation of methane emission rate from an oxidation lagoon using the static flow chamber technique and a low-cost methane sensor MQ-4. The study area was the oxidation lagoon “Bordo Los Puerquitos”, which receive wastewater from Cd. Victoria, Tamaulipas, México. Six sampling points were selected at the oxidation lagoon, and the methane concentration inside the static flow chamber was recorded over a 10-minute period. A linear regression analysis was realized to obtain the slop, which is equivalent to the methane emission rate. A slope comparation using a t-test after check of homoscedasticity of samples were performed. Spatial analysis using kriging interpolation was used to obtain the distribution of the methane emission rate at the lagoon and Voronoi polygons were used to determinate the influence area of each sampling point to obtain the weighted average emission of methane. The spatial analysis showed a south to north gradient of the CH4 emission rate with an average of 6.6 ± 3.3 ppm CH4 /min, the estimated emission of methane was 821.69 kg CH4/day. The results of this study are like those reported for a freshwater body with a slightly contaminated mesotrophic condition. The use of the static flow chamber with MQ-4 sensor for methane is a fast and low-cost methodology that can be used to estimate the contribution of GHGs from oxidation lagoons.