Chapter 5 Methane emission estimates from landfills obtained with dynamic plume measurements 1

Methane emissions from 3 different landfills in the Netherlands were estimated using a mobile Tuneable Diode Laser system (TDL). The methane concentration in the cross section of the plume is measured downwind of the source on a transect perpendicular to the wind direction. A Gaussian plume model was used to simulate the concentration levels at the transect. The emission from the source is calculated from the measured and modelled concentration levels. Calibration of the plume dispersion model is done using a tracer (N20) that is released from the landfill and measured simultaneously with the TDL system. The emission estimates for the different locations ranged from 3.6 to 16 m ha hr for the different sites. The emission levels were compared to emission estimates based on the landfill gas production modeIs. This comparison suggests oxidation rates that are up to 50% in spring and negligible in November. At one of the three sites measurements were performed in campaigns in 3 consecutive years. Comparison of the emission levels in the first and second year showed a reduction of the methane emission of about 50% due to implementation of a gas extraction system. From the second to the third year emissions increased by a factor of 4 due to new landfilling. Furthermore measurements were performed in winter when oxidation efficiency was reduced. This paper describes the measurement technique used, and discusses the results of the experimental sessions that were performed.