Spatial variability of nitrous oxide and methane emissions from an enMassai Barefoot TechnologyMBT landfill in operation: Strong N ₂O hotspots at the working face

Mechanical biological treatment (MBT) is an effective technique, which removes organic carbon from municipal solid waste (MSW) prior to deposition. Thereby, methane (CH4) production in the landfill is strongly mitigated. However, direct measurements of greenhouse gas emissions from full-scale MBT landfills have not been conducted so far. Thus, CH4 and nitrous oxide (N2O) emissions from a German MBT landfill in operation as well as their concentrations in the landfill gas (LFG) were measured. High N2O emissions of 20–200 g CO2 eq. m-2 h-1 magnitude (up to 428 mg N m-2 h-1) were observed within 20 m of the working face. CH4 emissions were highest at the landfill zone located at a distance of 30–40 m from the working face, where they reached about 10 g CO2 eq. m-2 h-1. The MBT material in this area has been deposited several weeks earlier. Maximum LFG concentration for N2O was 24.000 ppmv in material below the emission hotspot. At a depth of 50 cm from the landfill surface a strong negative correlation between N2O and CH4 concentrations was observed. From this and from the distribution pattern of extractable ammonium, nitrite, and nitrate it has been concluded that strong N2O production is associated with nitrification activity and the occurrence of nitrite and nitrate, which is initiated by oxygen input during waste deposition. Therefore, CH4 mitigation measures, which often employ aeration, could result in a net increase of GHG emissions due to increased N2O emissions, especially at MBT landfills.