Nitrous oxide and methane emissions from food waste composting at different temperatures.

Emissions of methane (CH₄) and nitrous oxide (N₂O) from composting of source-sorted food waste were studied at set temperatures of 40, 55 and 67°C in 10 trials performed in a controlled environment 200L compost reactor. CH₄ and N₂O concentrations were generally low. In trials with 16% O₂, the mean total CH₄ emission at all temperatures was 0.007% of the mineralized carbon (C), while at 67°C this fraction was 0.001%. Total CH₄ production was higher in the 40°C trial and the limited oxygen (1% O₂) trial, with emissions of 0.029 and 0.132% of the mineralized C respectively. An early increase in N₂O production was observed in trials with higher initial nitrate contents. Increased CH₄ and N₂O production in trials at 40 and 55°C after 50% of the initial C was mineralized resulted in higher total greenhouse gas emissions. Overall, the global warming potentials in CO₂-equivalents from CH₄ emissions were higher than from N₂O, except for composts run at 67°C.