Discrepancies in NO emissions between household waste and its food waste and non-food waste components during the predisposal stage.

Nitrous oxide (NO) 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 NO emissions were investigated. AN-labeled isotope experiment was conducted over three days to determine the contributions of nitrification and denitrification to NO emissions. The results showed that the NO fluxes first increased and then decreased during the three-day tests at different O concentrations. The maximum NO flux of 1469.59 ± 1004.32 μg N·kg wet waste·h occurred during the predisposal of food waste at an O concentration of 21%, with the total NO emissions reaching 20.26 ± 10.87 mg N·kg wet waste, which exceeds the emissions from some waste disposal processes, such as composting and landfills. The NO emissions decreased in the following order: food waste > household waste > non-food waste. For food waste, the peak value and total amount of NO emissions decreased significantly as the O concentration decreased. In contrast, the NO emissions from non-food waste increased as the O concentration decreased. Denitrification was the predominant biogenic source of NO emissions; it accounted for over 60% of NO production in all treatments. Nitrification also played an important role in NO emissions during the early predisposal stage.