Dynamics Of Non-controlled Emission Of Biogas From Landfills
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R N Lima, D Nolasco, J M L Salazar, P A Hernández & N M Pérez
To understand the dynamics of non-controlled emission of biogas from landfills several soil gas and CO2 efflux surveys were performed at the Arico landfill (Tenerife, Canary Islands). Estimated diffuse CO2 emissions for the Arico landfill (0.33 Km2) were 473 t d1(1998), 124 t d1(1999) and 44.7 t d-' (2001) and showed different spatial CO2 efflux patterns that can be explained in terms of new waste disposal and covering materials as well as the action of the biogas extraction system. Secular variations of diffuse CO2 efflux and meteorological parameters were measured hourly at one site in the center of the landfill for eleven months. Diffuse CO2 efflux ranged from 10 to 433 g m-2d1with a median value of 243 f73 g mm2 d-'. Diffuse CO2 efflux showed a temporal behavior that could be divided in two different periods: (a) a quasi-stationary period with minor fluctuations due to the influence of meteorological and soil variables, and (b) a non-stationary period with changing CO2 efflux values and major variations related to the preliminary tests on the biogas extraction system for the Arico landfill. Air and ground temperatures exhibit a significant positive correlation with the observed CO2 efflux. Peaks of maximum inverse correlation between barometric pressure and CO2 efflux are found at semi-diurnal and diurnal frequencies. Wind speed and wind direction are cross-correlated with CO2 efflux by 12 hours. These results suggest that (i) minor fluctuations in the CO2 efflux could be driven by meteorological variations (solar radiation cycles and local wind patterns), and (ii) sudden and major fluctuations in the CO2 efflux cannot be explained sufficiently in terms of the observed meteorological and soil variables' fluctuations.