Discrepancies in N2O emissions between household waste and its food waste and non-food waste components during the predisposal stage

Abstract

Nitrous oxide (N2O) is a greenhouse gas (GHG) and an ozone-depleting substance. Municipal solid waste (MSW) management and treatment activities are some of the sources of GHG emissions. However, the biogenic GHG emissions during the predisposal stage of MSW management, during which waste is transferred to garbage cans and then transported to disposal sites, have received little attention. In this study, household waste was divided into food and non-food waste, and the effects of these types of waste and different oxygen concentrations (21%, 10%, and 1%) on N2O emissions were investigated. A15N-labeled isotope experiment was conducted over three days to determine the contributions of nitrification and denitrification to N2O emissions. The results showed that the N2O fluxes first increased and then decreased during the three-day tests at different O2 concentrations. The maximum N2O flux of 1469.59 ± 1004.32 μg N·kg−1 wet waste·h−1 occurred during the predisposal of food waste at an O2 concentration of 21%, with the total N2O emissions reaching 20.26 ± 10.87 mg N·kg−1 wet waste, which exceeds the emissions from some waste disposal processes, such as composting and landfills. The N2O emissions decreased in the following order: food waste > household waste > non-food waste. For food waste, the peak value and total amount of N2O emissions decreased significantly as the O2 concentration decreased. In contrast, the N2O emissions from non-food waste increased as the O2 concentration decreased. Denitrification was the predominant biogenic source of N2O emissions; it accounted for over 60% of N2O production in all treatments. Nitrification also played an important role in N2O emissions during the early predisposal stage.