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| Yuhei INAMORI | |
| Head, International Water Environment Renovation Research Team | |
| Division of Regional Environment | |
| National Institute for Environmental Studies, | |
| 16-2 Onogawa, Tsukuba, Ibaraki, 3050053, Japan | |
| Tel: +81-298-50-2496 Fax: +81-298-50-2570 | |
| Email: inamori@nies.go.jp |
¡¡4,919,000 Yen
¡¡(FY 1999: 2,414,000 Yen)
¡¡Emissions of N2O and CH4 from aerated composting system were investigated using small-scale simulated reactors. The results show an emission peak of N2O at the beginning of composting in all experimental runs. Nitrous oxide level in the exhausted gas is proportion to the application amount of food waste. After 2 days, N2O concentration at air outlet decreases to 0.53ul¥Ì-1 in average, near to the background level in the atmosphere (0.45 ul¥Ì-1). Addition of compost increased N2O emission not only at the beginning of composting, but also during the later period and resulted in two-peak emission curves. Good correlation was observed between N2O concentration at the air outlet and NO2- concentration in waste, indicating a generation pathway for N2O from NO2- to N2O. The phenomenon was further certified by an external addition of nitrite into waste mixture, With the nitrite shock, extremely high N2O generation was observed in both compost-applied and non-compost treatments, suggesting the existence of same mechanism for N2O production. Nitrous oxide mainly results from the accumulation of nitrite in waste mixture. In compost-applied treatments obvious nitrite accumulation was detected whereas in non-compost treatments most nitrogen was lost by ammonia volatilization and no clear nitrite accumulation was found. Therefore, to reduce N2O production, nitrite accumulation should be avoided.
¡¡Addition pattern of food waste may also affect N2O production. Daily-addition and multi-addition of food waste result into lower N2O emission than single addition. Involvement of more carbon source prolongs the ammonification period and postpones N2O generation.
¡¡Methane was only detected in treatments applied with compost, the high emission of it illustrate the involvement of anoxic/anaerobic microorganisms with the addition of compost. The result suggests the existence of anoxic or anaerobic microsite inside the waste particles even though aeration was employed during composting process.
¡¡N2O emission, Methane emission, Food waste, Composting, greenhouse gases