Life-Cycle Assessment of a Regulatory Compliant U.S. Municipal Solid Waste Landfill

Landfills receive over half of all U.S. municipal solid waste (MSW) and are the third largest source of anthropogenic methane emissions. Life-cycle assessment (LCA) of landfills is complicated by the long duration of waste disposal, gas generation and control, and the time over which the engineered infrastructure must perform. The objective of this study is to develop an LCA model for a representative U.S. MSW landfill that is responsive to landfill size, regulatory thresholds for landfill gas (LFG) collection and control, practices for LFG management (i.e., passive venting, flare, combustion for energy recovery), and four alternative schedules for LFG collection well installation. Material production required for construction and operation contributes 68–75% to toxicity impacts, while LFG emissions contribute 50–99% to global warming, ozone depletion, and smog impacts. The current non-methane organic compound regulatory threshold (34 Mg yr–1) reduces methane emissions by –1). Requiring landfills to continue collecting LFG until the flow rate is 3 min–1 reduces emissions by 20–52%, depending on the waste decay rate. In general, for landfills already required to collect gas, collecting gas longer is more important than collecting gas earlier to reduce methane emissions.美国填埋场接纳了超过半数的城市固体废物（Municipal Solid Waste, MSW），是全球第三大人为甲烷排放源。由于废物处置、产气与管控周期漫长，且工程化基础设施需长期服役，填埋场的生命周期评估（Life-cycle Assessment, LCA）复杂度较高。本研究旨在针对具有代表性的美国城市固体废物填埋场，开发一套可适配填埋场规模、填埋气（Landfill Gas, LFG）收集与管控的监管阈值、填埋气管理实践（即被动通风、火炬燃烧、能量回收式燃烧）以及四种填埋气收集井安装备选方案的生命周期评估模型。研究结果显示，填埋场建设与运营所需的材料生产环节对毒性影响的贡献占比达68%~75%；而填埋气排放则分别对全球变暖、臭氧消耗及光化学烟雾的影响贡献了50%~99%。当前非甲烷有机物监管阈值（34 兆克/年）可使甲烷排放量降低约1%（原文此处“–1)”疑似输入疏漏）。要求填埋场持续收集填埋气直至气流量降至3 立方米/分钟，该要求可根据废物降解速率的不同，使甲烷减排量达到20%~52%。总体而言，对于已被要求开展填埋气收集的填埋场而言，相较于提前开展收集，延长填埋气收集时长对降低甲烷排放的效果更为显著。