家庭廃棄物とその食品廃棄物と非食品廃棄物の構成要素の間のNO排出量の不一致

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

• Hualiang Feng
• Xiaojun Wang
• Jiasheng Cai
• Shaohua Chen

抄録

亜酸化窒素（NO）は温室効果ガス（GHG）であり、オゾン層破壊物質である。都市ごみ（MSW）の管理・処理活動は、温室効果ガスの排出源の一つである。しかし、ごみがごみ箱に運ばれて処分場に運ばれる過程での生物起源のGHG排出については、これまであまり注目されていませんでした。本研究では、家庭ごみを生ごみと非生ごみに分け、これらのごみの種類と酸素濃度（21％，10％，1％）の違いがNO排出量に及ぼす影響を調べた。AN標識同位体実験を3日間実施し、NO排出量に対する硝化と脱窒の寄与を調べた。その結果、NOフラックスは、異なるO濃度で3日間の試験中に最初に増加し、その後減少することが示された。その結果、O濃度21%の食品廃棄物の予処分中に最大のNOフラックス1469.59±1004.32μgN-kg湿潤廃棄物-hが発生し、総NO排出量は20.26±10.87mgN-kg湿潤廃棄物に達し、これは堆肥化や埋め立てなどの廃棄物処理プロセスからの排出量を上回るものであった。NO排出量は、食品廃棄物＞家庭廃棄物＞非食品廃棄物の順に減少しました。生ごみでは、O濃度の低下に伴い、ピーク値と総排出量が大きく減少しました。一方、非生鮮廃棄物からのNOx排出量は、O濃度の低下に伴って増加した。NO排出の主な生物起源源は脱窒であり、すべての処理でNO生成量の60%以上を占めていた。窒素化もまた、初期の予備処分段階ではNO排出に重要な役割を果たしていた。

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.

Copyright © 2020 Elsevier Ltd. All rights reserved.