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 <7% relative to the former threshold (50 Mg yr −1 ). Requiring landfills to continue collecting LFG until the flow rate is <10 m 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.

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Landfills are a major contributor of anthropogenic CH 4 emissions. Since the greenhouse gas (GHG) emissions associated with landfilling waste can occur over decades to centuries, the standard static approach to estimating global warming impacts may not accurately represent the global warming impacts of landfills. The objective of this study is to assess the implications of using 100 yr and 20 yr static and dynamic global warming potential (GWP) approaches to estimate the global warming impacts from municipal solid waste landfills. A life-cycle model was developed to estimate GHG emissions for three gas treatment cases (passive venting, flare, CH 4 conversion to electricity) and four decay rates. For the 100 yr GWP, other model uncertainties (e.g., static GWP values, decay rate, moisture content, or gas collection efficiency) generally had a larger effect on the estimated global warming impact than the choice of static versus dynamic GWP methods. This shows that when comparing single-point GWP values, the choice of static versus dynamic is relatively unimportant for most landfills. While dynamic GWPs consider temporal variance and provide useful estimates for the warming over a set time horizon, for most comparative analyses, static values provide reasonable bounds for the actual 100 yr warming impact.

This study summarized global examples of landfill slope instability over the past 40 years, then selected 62 cases from 22 different counties to analyse the primary factors causing landfill instability. Three slope instability modes in landfill were categorized according to the position of the slip surface: (1) slip surfaces generated inside the waste pile; (2) slip surfaces that pass through the foundation soil; and (3) slip surfaces that occur along the interface between the bottom liner and the municipal solid waste (MSW) pile. These three types of slope instability modes account for 69.4%, 19.32% and 11.28% of all slope instability, respectively. Moreover, five primary causes of landfill instability were identified. A high landfill leachate level was the dominant cause, accounting for 40.32% of cases. This was followed by inadequate compaction of MSW, which accounted for 22.58% of cases, and insufficiently bearing capacity of the foundation, which accounted for 19.35% of cases. Moreover, low shear strength of the liner–MSW interface and rapid release or deflagration of landfill gas were critical factors affecting landfill stability. Factors of safety were calculated using GeoStudio software for selected landfills in China (Maoershan and Xiaping) and Sri Lanka (Meethotamulla). Results from this study are expected to contribute to the prevention and control of landfill failure.

Life-cycle assessments (LCAs) of municipal solid waste management (MSWM) systems are time- and data-intensive. Reducing the data requirements for inventory and impact assessments will facilitate the wider use of LCAs during early system planning and design. Therefore, the objective of this study is to develop a systematic framework for streamlining LCAs by identifying the most critical impacts, life-cycle inventory emissions, and inputs based on their contributions to the total impacts and their effect on the rankings of 18 alternative MSWM scenarios. The scenarios are composed of six treatment processes: landfills, waste-to-energy combustion, single-stream recycling, mixed waste recycling, anaerobic digestion, and composting. The full LCA uses 1752 flows of resources and emissions, 10 impact categories, 3 normalization references, and 7 weighting schemes, and these were reduced using the streamlined LCA approach proposed in this study. Human health cancer, ecotoxicity, eutrophication, and fossil fuel depletion contribute 75–83% to the total impacts across all scenarios. It was found that 3.3% of the inventory flows contribute ≥95% of the overall environmental impact. The highest-ranked strategies are consistent between the streamlined and full LCAs. The results provide guidance on which impacts, flows, and inputs to prioritize during early strategy design.