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Elevated per- and polyfluoroalkyl substance (PFAS) concentrations have been reported in municipal solid waste (MSW) landfill leachate with higher levels in wet and warmer subtropical climates. Information about landfill leachate characteristics is much more limited in tropical climates. In this study, 20 landfill leachate samples were collected from three MSW landfills on the tropical island of Puerto Rico and results were compared against landfills nationally and within Florida, USA. The samples collected in Puerto Rico underwent physical-chemical analysis, as well as a quantitative analysis of 92 PFAS. Samples described in this study include discrete leachate types, such as leachate, gas condensate, and leachate which has undergone on-site treatment (e.g., RO treatment, phytoremediation, lagoons). A total of 51 PFAS were detected above quantitation limits, including perfluorohexylphosphonic acid, a perfluoroalkyl acid (PFAA) which has not been reported previously in landfill leachate. ∑PFAS concentrations in this study (mean: 38,000 ng L -1 ), as well as concentrations of individual PFAS, are significantly higher than other reported MSW landfill leachate concentrations. The profiles of leachates collected from on-site treatment systems indicate possible transformation of precursor PFAS as a result of treatment processes - oxidizing conditions, for example, may facilitate aerobic transformation, increase the concentrations of PFAAs, and possibly increase the apparent ∑PFAS concentration. Extreme climate events, including rising temperatures and more frequent hurricanes, have placed additional strain on the solid waste management infrastructure on the island - adding complexity to an already challenging PFAS management issue. As concern grows over PFAS contamination in drinking water, these findings should inform solid waste and leachate management decisions in order to minimize PFAS emissions in island environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

A critical examination of the US Environmental Protection Agency's (US EPA's) Greenhouse Gas Reporting Program (GHGRP) database provided an opportunity for the largest evaluation to date of landfilled waste decomposition kinetics with respect to different US climate regimes. In this paper, 5-8 years of annual methane collection data from 114 closed landfills located in 29 states were used to estimate site-specific waste decay rates (k) and methane collection potentials (Lc). These sites account for approximately 9% of all landfills required to report GHG emissions to the US EPA annually. The mean methane collection potential (Lc) for the sites located in regions with less than 635 mm (25 in) annual rainfall was significantly (p<0.002) lower than the mean methane collection potential of the sites located in regions with more than 635 mm (25 in) annual precipitation (49 and 73 m3 methane Mg-1 waste, respectively). This finding suggests that a fraction of the in-place biodegradable waste may not be decomposing, potentially due to a lack of adequate moisture content of landfills located in arid regions. The results of this evaluation offer insight that challenges assumptions of the traditional landfill methane estimation approach, especially in arid climates, that all methane corresponding to the total methane generation potential of the buried solid waste will be produced. Decay rates showed a significant correlation with annual precipitation, with an average k of 0.043 year-1 for arid regions (< 508 mm (20 in) year-1), 0.074 year-1 for regions with 508-1,016 mm (20-40 in) annual precipitation, and 0.09 year-1 in wet regions (> 1,016 mm (40 in) year-1). The data suggest that waste is decaying faster than the model default values, which in turn suggests that a larger fraction of methane is produced during a landfill's operating life (relative to post-closure)., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The employment of Pradeep Jain and James Wally with Innovative Waste Consulting Services LLC does not alter our adherence to PLOS ONE policies on sharing data and materials.

The fate of antimony (Sb) leached from electronic and electrical equipment plastic when disposed of in a municipal solid waste (MSW) landfill was assessed using simulated anaerobic landfill lysimeters and three different batch leaching tests: toxicity characteristic leaching procedure (TCLP), EPA method 1313, and MSW leachate extractions. Plastic from cathode ray tube televisions sets was noted to have the highest Sb concentrations, and was thus the focus of the study. Sb leachability from EPA 1313 stat and TCLP were similar at approximately 0.1% by weight at the same pH (4.93), while MSW landfill leachates extracted less Sb at approximately 0.02% by weight. Solution pH was not the controlling factor, and other conditions resulting from the landfill leachate resulted in lower concentrations of leached Sb. In simulated landfill experiments, Sb leached at approximately 0.01% by weight after a liquid-to-solid ratio of 3. Sb behaves differently in the landfill environment than arsenic leaching from a similar study, most likely from the reducing conditions brought on by the decomposing waste., (Copyright © 2019. Published by Elsevier Ltd.)

National generation estimates for seven material types in the construction and demolition debris stream are regularly published in the United States. However, the quantities of these materials in different end-of-life management pathways are not published or otherwise made available. Quantification of end-of-life management pathways is useful for identifying approaches to decrease disposal and increase material recovery. An issue for construction and demolition debris is that data needed for a nationwide estimate of management pathways are not tracked in a single system. We propose and outline a method that draws on a combination of data sources, including nationwide generation estimates, state data, industry association data, and recovery facility reports. Capturing the available data and using the proposed method, we can estimate what end-of-life pathways are used for the seven materials in the US Environmental Protection Agency's annual reports of CDD generation (steel, wood products, drywall and plaster, brick and clay tile, asphalt shingles, concrete and asphalt concrete), and five additional materials managed within the CDD waste stream (carpet, plastic, glass, cardboard and organics). Method results indicate that the vast majority of CDD concrete and asphalt pavement, which in 2014 constituted ∼78% of the overall mass of the stream's components, were reclaimed for use, primarily in road projects. A significant opportunity for material recovery still exists for the remaining ∼22% of the stream. In 2014, approximately 64% of these remaining materials in the US was ultimately routed for landfill disposal., (Published by Elsevier Ltd.)

Methane generation potential, L 0 , is a primary parameter of the first-order decay (FOD) model used for prediction and regulation of landfill gas (LFG) generation in municipal solid waste (MSW) landfills. The current US EPA AP-42 default value for L 0 , which has been in place for almost 20 years, is 100 m 3 CH 4 /Mg MSW as-discarded. Recent research suggests the yield of landfilled waste could be less than 60 m 3 CH 4 /Mg MSW. This study aimed to measure the L 0 of present-day residential and commercial as-discarded MSW. In doing so, 39 waste collection vehicles were sorted for composition before samples of each biodegradable fraction were analyzed for methane generation potential. Methane yields were determined for over 450 samples of 14 different biodegradable MSW fractions, later to be combined with moisture content and volatile solids data to calculate L 0 values for each waste load. An average value of 80 m 3 CH 4 /Mg MSW was determined for all samples with 95% of values in the interval 74-86 m 3 CH 4 /Mg MSW as-discarded. While no statistically significant difference was observed, commercial MSW yields (mean 85, median 88 m 3 CH 4 /Mg MSW) showed a higher average L 0 than residential MSW (mean 75, median 71 m 3 CH 4 /Mg MSW). Many methane potential values for individual fractions described in previous work were found within the range of values determined by BMP in this study., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Samples of leachate were collected from fourteen landfills in the state of Florida, United States that contained primarily putrescible waste (municipal solid waste, MSW, and yard waste), MSW incinerator (MSWI) ash, or a combination of both. Assessment of leachates included trace metals, anions, and nutrients in order to create a mass balance of total dissolved solids (TDS). As expected from previously literature, MSW leached a complex matrix of contaminants while MSWI ash leachate TDS was more than 98% metallic salts. The pH of the MSWI ash leachate samples was slightly acidic or neutral in character, which is contradictory to the results commonly reported in the literature. The cause of this is hypothesized to be a short-circuiting of rainfall in the landfill due to low hydraulic conductivities reported in ash landfills. The difference in pH likely contributed to the findings with respect to MSWI ash-characteristic trace metals in leachates such as aluminum. The authors have concluded that the research findings in this study are an indication of the differences between laboratory leachate quality studies and the conditions encountered in the field. In addition, a characterization of organic matter using qualitative and quantitative analyses determined that COD is not an accurate indicator of organic matter in leachates from landfills with a significant fraction of MSWI ash., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Vertical liquids addition systems have been used at municipal landfills as a leachate management method and to enhance biostabilization of waste. Drawbacks of these systems include a limitation on pressurized injection and the occurrence of seepage. A novel vertical well system that employed buried wells constructed below a lift of compacted waste was operated for 153 days at a landfill in Florida, USA. The system included 54 wells installed in six clusters of nine wells connected with a horizontally-oriented manifold system. A cumulative volume of 8430 m 3 of leachate was added intermittently into the well clusters over the duration of the project with no incidence of surface seeps. Achievable average flow rates ranged from 9.3 × 10 -4 m 3 s -1 to 14.2 × 10 -4 m 3 s -1 , which was similar to or greater than flow rates achieved in a previous study using traditional vertical wells at the same landfill site. The results demonstrated that pressurized liquids addition in vertical wells at municipal solid waste landfills can be achieved while avoiding typical operational and maintenance issues associated with seeps., (© The Author(s) 2016.)

Landfill gas (LFG) generation is predicted by a first-order decay (FOD) equation that incorporates two parameters: a methane generation potential (L 0 ) and a methane generation rate (k). Because non-hazardous waste landfills may accept many types of waste streams, multiphase models have been developed in an attempt to more accurately predict methane generation from heterogeneous waste streams. The ability of a single-phase FOD model to predict methane generation using weighted-average methane generation parameters and tonnages translated from multiphase models was assessed in two exercises. In the first exercise, waste composition from four Danish landfills represented by low-biodegradable waste streams was modeled in the Afvalzorg Multiphase Model and methane generation was compared to the single-phase Intergovernmental Panel on Climate Change (IPCC) Waste Model and LandGEM. In the second exercise, waste composition represented by IPCC waste components was modeled in the multiphase IPCC and compared to single-phase LandGEM and Australia's Solid Waste Calculator (SWC). In both cases, weight-averaging of methane generation parameters from waste composition data in single-phase models was effective in predicting cumulative methane generation from -7% to +6% of the multiphase models. The results underscore the understanding that multiphase models will not necessarily improve LFG generation prediction because the uncertainty of the method rests largely within the input parameters. A unique method of calculating the methane generation rate constant by mass of anaerobically degradable carbon was presented (k c ) and compared to existing methods, providing a better fit in 3 of 8 scenarios. Generally, single phase models with weighted-average inputs can accurately predict methane generation from multiple waste streams with varied characteristics; weighted averages should therefore be used instead of regional default values when comparing models., Implications: Translating multiphase first-order decay model input parameters by weighted average shows that single-phase models can predict cumulative methane generation within the level of uncertainty of many of the input parameters as defined by the Intergovernmental Panel on Climate Change (IPCC), which indicates that decreasing the uncertainty of the input parameters will make the model more accurate rather than adding multiple phases or input parameters.

More than 1,500 construction and demolition debris (CDD) landfills operate in the United States (U.S.), and U.S. federal regulations do not require containment features such as low-permeability liners and leachate collection systems for these facilities. Here we evaluate groundwater quality from samples collected in groundwater monitoring networks at 91 unlined, permitted CDD landfills in Florida, U.S. A total of 460,504 groundwater sample results were analyzed, with a median of 10 years of quarterly or semiannual monitoring data per site including more than 400 different chemical constituents. Downgradient concentrations of total dissolved solids, sulfate, chloride, iron, ammonia-nitrogen, and aluminum were greater than upgradient concentrations (p < 0.05). At downgradient wells where sulfate concentrations were greater than 150 mg/L (approximately 10% of the maximum dissolved sulfate concentration in water, which suggests the presence of leachate from the landfill), iron and arsenic were detected in 91% and 43% of samples, with median concentrations of 1,900 μg/L and 11 μg/L, respectively. These results show that although health-based standards can be exceeded at unlined CDD landfills, the magnitude of detected chemical concentrations is generally small and reflective of leached minerals from components (wood, concrete, and gypsum drywall) that comprise the bulk of discarded CDD by mass.

Waste hydraulic conductivity and anisotropy represent two important parameters controlling fluid movement in landfills, and thus are the key inputs in design methods where predictions of moisture movement are necessary. Although municipal waste hydraulic conductivity has been estimated in multiple laboratory and field studies, measurements of anisotropy, particularly at full scale, are rare, even though landfilled municipal waste is generally understood to be anisotropic. Measurements from a buried liquids injection well surrounded by pressure transducers at a full-scale landfill in Florida were collected and examined to provide an estimate of in-situ waste anisotropy. Liquids injection was performed at a constant pressure and the resulting pore pressures in the surrounding waste were monitored. Numerical fluid flow modeling was employed to simulate the pore pressures expected to occur under the conditions operated. Nine different simulations were performed at three different lateral hydraulic conductivity values and three different anisotropy values. Measured flowrate and pore pressures collected from conditions of approximate steady state were compared with the simulation results to assess the range of anisotropies. The results support that compacted municipal waste in landfills is anisotropic, provide anisotropy estimates greater than previous measurements, and suggest that anisotropy decreases with landfill depth., (© The Author(s) 2014.)

Recent research and policy directives have emerged with a focus on sustainable management of waste materials, and the mining of old landfills represents an opportunity to meet sustainability goals by reducing the release of liquid- and gas-phase contaminants into the environment, recovering land for more productive use, and recovering energy from the landfilled materials. The emissions associated with the landfill mining process (waste excavation, screening, and on-site transportation) were inventoried on the basis of diesel fuel consumption data from two full-scale mining projects (1.3-1.5 L/in-place m(3) of landfill space mined) and unit emissions (mass per liter of diesel consumption) from heavy equipment typically deployed for mining landfills. An analytical framework was developed and used in an assessment of the life-cycle environmental impacts of a few end-use management options for materials deposited and mined from an unlined landfill. The results showed that substantial greenhouse gas emission reductions can be realized in both the waste relocation and materials and energy recovery scenarios compared to a "do nothing" case. The recovery of metal components from landfilled waste was found to have the greatest benefit across nearly all impact categories evaluated, while emissions associated with heavy equipment to mine the waste itself were found to be negligible compared to the benefits that mining provided.