RESUMO
Biocover systems are a cost-effective technology utilised to mitigate methane (CH4) and trace gas emissions from landfills. A full-scale biofilter system was constructed at Glatved landfill, Denmark, consisting of three biofilters with a total area of 3950 m2. Landfill gas collected mainly from shredder waste cells was mixed with ambient air and fed actively into the biofilter, resulting in an average load of 60-75 g m-2 d-1 for CH4 and 0.15-0.21 g m-2 d-1 for trace gases (e.g., aromatics, chlorofluorocarbons (CFCs), aliphatic hydrocarbons). The initial CH4 surface screening showed uneven gas distribution into the system, and elevated surface concentrations were observed close to the gas inlet. Both positive and negative CH4 fluxes, ranging from -0.36 to 4.25 g m-2 d-1, were measured across the surface of the biofilter. Total trace gas emissions were between -0.005 and 0.042 g m-2 d-1, and the emission flux of individual compounds were generally small (10-8 to 10-3 g m-2 d-1). Vertical gas concentration profiles showed that the oxidation of CH4 and easily degradable trace compounds such as aromatics and aliphatic hydrocarbons happened in the aerobic zones, while CFCs were degraded in the anaerobic zone inside the compost layer. In addition, oxidation/degradation of CH4 and trace gases also occurred in the gas distribution layer, which contributed significantly to the overall mitigation efficiency of the biofilter system. Overall, the biofilter system showed mitigation efficiencies of nearly 100% for both CH4 and trace gases, and it might have the potential to work under higher loads.
