Emissões fugitivas de CH4 e CO2 em camadas de cobertura de um aterro sanitário do Estado do Ceará

Abstract

The aim of this study was to evaluate the gas flow behavior (CH4 and CO2) by the final cover layer of a solid waste cell at Caucaia-Ceará Landfill. Four points were chosen on the lower berm and four on the upper one. Emission estimations were made through static flow plate tests connected to the GEM5000 reader, measuring concentrations of oxygen (%), carbon monoxide (ppm), carbon dioxide (%) and methane (%), in addition to temperature (°C), pressure (mb) and gas flow (m3/h). In the lower berm, there was a clear tendency of flow increase from site one to site four, for both gases, indicating the existence of preferential paths or higher oxidation rates in site one. The CH4 flux ranged from 9.8 x 10-2 and 5.3 x 10-1 m3/m2.h and CO2 varied from 6.6 x 10-2 to 3.9 x 10- 1 m3/m2.h. In the upper berm, there was another pattern, since the CO2 flux (2.0 x 10-1 - 3.3 x 10- 1 m3/m2.h) was greater than that of CH4 (6.6 x 10-2 and 2.6 x 10-1 m3/m2.h). Gas concentration profiles had significant variability in short distances of cover soil. In addition, the solid wastes under the lower berm seem to be in degradation phase 4 (methanogenic) while the wastes under the upper berm seem to be in degradation phase 3 (acidogenic).