Fugitive methane emissions from two experimental biocovers constructed with tropical residual soils: field study using a large flux chamber

Abstract

Abstract: This study aimed at assessing the response of two experimental passive methane oxidation biocovers (PMOB) installed in a Brazilian landfill located in Guarapuava, State of Paraná. The PMOBs covered an area of 18 m² each, and were 0.70-m-thick. The first PMOB (control subarea) was constructed using the same soil used to cover closed landfill cells, i.e. a typical residual soil. The second PMOB (enriched subarea) was constructed with a mixture of the residual soil and mature compost, with a resulting organic matter content equal to 4.5%. CH4 and CO2 surface fluxes were measured in a relatively large (4.5 m²) static chamber. CH4, CO2 and O2 concentrations were also measured at different depths (0.10, 0.20, 0.25 and 0.30 m) within PMOBs. The concentrations from the raw biogas were also measured. Methane oxidation efficiencies (Effox) were estimated based on the CO2/CH4 ratio. The average CH4 and CO2 concentrations in the raw biogas (42% and 32%, respectively) for the 16 campaigns corroborated those typically found in Brazilian landfills. Lower CH4 fluxes were obtained within the enriched subarea (average of 20 g.m-2.d-1), while the fluxes in the control subarea averaged 34 g.m-2.d-1. Effox values averaged 42% for the control subarea and 80% for the enriched one. The results indicate that there is a great potential to reduce landfill gas (LFG) emissions by using passive methane oxidation biosystems composed of enriched substrates (with a higher content of organic matter).