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Waste-sector greenhouse gas emissions have long been accepted as a critical component of climate change mitigation efforts because of the significant radiative forcing of methane (CH4) production from municipal landfills and other emissions from waste management processes. In developed countries, waste generation is expected to peak and decline by the end of the century, whereas waste generation is rapidly rising in many developing nations. The extent to which the countries of the world are planning to handle future quantities of waste has not been explored in detail. This work provides the first detailed account of future waste management planning and waste-sector mitigation strategies through an analysis of stated commitments in the 174 Nationally Determined Contributions (NDCs, documents outlining each country's actions to mitigate carbon emissions and adapt to a changing climate) that have been filed to date within the Framework Convention on Climate Change secretariat in Bonn. One-hundred thirty-seven of 174 countries that submitted NDCs included waste-sector emission mitigation actions, representing approximately 85% of all global emissions. About half (67) of the countries that included waste sector mitigation tactics identified infrastructure or policy actions to meet mitigation commitments, but these strategies vary widely in their scope and level of detail. Landfilling was the most commonly-cited waste-sector commitment (n = 47), followed by deriving energy from waste through various techniques (n = 42). Countries targeting improved solid waste collections had less extensive coverage (µcollection = 38% of generated waste collected) than countries that did not prioritize improved collections (µcollection = 46% of waste generation), but countries not prioritizing the waste sector at all in NDCs had the most limited waste collection coverage (µcollection = 33%). Almost all of the countries that specified emissions inventory assumptions (132 of 135) use outdated CH4 global warming potential values which, coupled with missing or poor waste management data suggests many countries may be underestimating the importance of waste sector emissions in national emissions portfolios. Several examples of data collection and reporting models are identified that can help to inform and potentially improve life-cycle environmental outcomes in the waste sector. Adaptation strategies detailed in NDCs have largely overlooked the waste sector, suggesting inadequate incorporation of future climate scenarios in waste sector infrastructure planning.

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Waste generation is expected to increase in most countries for many decades with landfill disposal still the dominant solid waste management method1-3. Yet, operational characteristics of landfills are often poorly understood with comparative statistics substantially lacking. Here, we call for a more formal waste informatics to organize and standardize waste management knowledge at multiple spatial scales through analysis of recently reported data from 1232 U.S. landfills and other high resolution data sets. We create the first known estimate of available U.S. municipal waste stocks (8.5 billion tonnes) and go on to resolve these stocks at the county level, reflecting prospective urban mining opportunities. Our analysis of disposal rates and landfill capacities reveals that more than half of U.S. states have more than 25 years of life remaining. We also estimate the gross energy potential of landfill gas in the U.S. (338 billion MJ/yr) by examining 922 operational methane collection systems and demonstrate that the greatest energy recovery opportunities lie at landfills with existing collection systems and energy conversion infrastructure. Finally, we found that the number of landfills reaching the federally defined 30-year postclosure care period will more than triple in the coming two decades, with 264 sites expected by the year 2044, highlighting the need to develop and standardize metrics carefully to define and standardize when it is appropriate to end or scale back long-term landfill monitoring.

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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 m3 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 m3 s-1 to 14.2 × 10-4 m3 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.

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High concentrations of iron (Fe(II)) and manganese (Mn(II)) reductively dissolved from soil minerals have been detected in groundwater monitoring wells near many municipal solid waste landfills. Two in situ permeable reactive barriers (PRBs), comprised of limestone and crushed concrete, were installed downgradient of a closed, unlined landfill in Florida, USA, to remediate groundwater containing high concentrations of these metals. Influent groundwater to the PRBs contained mean Fe and Mn concentrations of approximately 30mg/L and 1.62mg/L, respectively. PRBs were constructed in the shallow aquifer (maximum depth 4.6m below land surface) and groundwater was sampled from a network of nearby monitoring wells to evaluate barrier performance in removing these metals. PRBs significantly (p<0.05) removed dissolved Fe and Mn from influent groundwater; Fe was removed from influent water at average rates of 91% and 95% (by mass) for the limestone and crushed concrete PRBs, respectively, during the first year of the study. The performance of the PRBs declined after 3years of operation, with Fe removal efficiency decreasing to 64% and 61% for limestone and concrete PRBs, respectively. A comparison of water quality in shallow and deep monitoring wells showed a more dramatic performance reduction in the deeper section of the concrete PRB, which was attributed to an influx of sediment into the barrier and settling of particulates from the upper portions of the PRBs. Although removal of Fe and Mn from redox impacts was achieved with the PRBs, the short time frame of effectiveness relative to the duration of a full-scale remediation effort may limit the applicability of these systems at some landfills because of the construction costs required.

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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.

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A case study of landfill liquids addition using small diameter (5 cm) vertical wells is reported. More than 25,000 m(3) of leachate was added via 134 vertical wells installed 3 m, 12 m, and 18 m deep over five years in a landfill in Florida, US. Liquids addition performance (flow rate per unit screen length per unit liquid head) ranged from 5.6×10(-8) to 3.6×10(-6) m(3) s(-1) per m screen length per m liquid head. The estimated radial hydraulic conductivity ranged from 3.5×10(-6) to 4.2×10(-4) m s(-1). The extent of lateral moisture movement ranged from 8 to 10 m based on the responses of moisture sensors installed around vertical well clusters, and surface seeps were found to limit the achievable liquids addition rates, despite the use of concrete collars under a pressurized liquids addition scenario. The average moisture content before (51 samples) and after (272 samples) the recirculation experiments were 23% (wet weight basis) and 45% (wet weight basis), respectively, and biochemical methane potential measurements of excavated waste indicated significant (p<0.025) decomposition.

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High concentrations of iron (Fe(II)) and manganese (Mn(II)) reductively dissolved from soil minerals have been detected in groundwater monitoring wells near many municipal solid waste landfills. Air sparging and vadose zone aeration (VZA) were evaluated as remedial approaches at a closed, unlined municipal solid waste landfill in Florida, USA. The goal of aeration was to oxidize Fe and Mn to their respective immobile forms. VZA and shallow air sparging using a partially submerged well screen were employed with limited success (Phase 1); decreases in dissolved iron were observed in three of nine monitoring wells during shallow air sparging and in two of 17 wells at VZA locations. During Phase 2, where deeper air sparging was employed, dissolved iron levels decreased in a significantly greater number of monitoring wells surrounding injection points, however no radial pattern was observed. Additionally, in wells affected positively by air sparging (mean total iron (FeTOT) <4.2mg/L, after commencement of air sparging), rising manganese concentrations were observed, indicating that the redox potential of the groundwater moved from an iron-reducing to a manganese-reducing environment. The mean FeTOT concentration observed in affected monitoring wells throughout the study was 1.40 mg/L compared to a background of 15.38 mg/L, while the mean Mn concentration was 0.60 mg/L compared to a background level of 0.27 mg/L. Reference wells located beyond the influence of air sparging areas showed little variation in FeTOT and Mn, indicating the observed effects were the result of air injection activities at study locations and not a natural phenomenon. Air sparging was found effective in intercepting plumes of dissolved Fe surrounding municipal landfills, but the effect on dissolved Mn was contrary to the desired outcome of decreased Mn groundwater concentrations.

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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.

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The emission of H2S from landfills in the United States is an emergent problem because measured concentrations within the waste mass and in ambient air have been observed at potentially unsafe levels for on-site workers and at levels that can cause a nuisance and potentially deleterious health impacts to surrounding communities. Though recent research has provided data on H2S concentrations that may be observed at landfills, facility operators and landfill engineers have limited predictive tools to anticipate and plan for potentially harmful H2S emissions. A one-dimensional gas migration model was developed to assist engineers and practitioners better evaluate and predict potential emission levels of H2S based on four factors: concentration of H2S below the landfill surface (C0), advection velocity (v), H2S effective diffusion coefficient (D), and H2S adsorption coefficient of landfill cover soil (µ). Model simulations indicated that H2S migration into the atmosphere can be mitigated by reducing H2S diffusion and advection or using alternative cover soils with a high H2S adsorption coefficient. Laboratory column experiments were conducted to investigate the effects of the four parameters on H2S migration in cover soils and to calculate the adsorption coefficient of different cover materials. The model was validated by comparing results with laboratory column experiments. Based on the results, the laboratory column provides an effective way to estimate the H2S adsorption coefficient, which can then be incorporated into the developed model to predict the depth of cover soil required to reduce emitted H2S concentrations below a desired level.

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OBJECTIVE: To develop an observational coding instrument for evaluating the fidelity and quality of brief behavioral change interventions based on the behavioral theories of the 5 A's, Stages of Change and Motivational Interviewing. METHODS: Content and face validity were assessed prior to an intervention where psychometric properties were evaluated with a prospective cohort of 116 medical students. Properties assessed included the inter-rater reliability of the instrument, internal consistency of the full scale and sub-scales and descriptive statistics of the instrument. Construct validity was assessed based on student's scores. RESULTS: Inter-rater reliability for the instrument was 0.82 (intraclass correlation). Internal consistency for the full scale was 0.70 (KR20). Internal consistencies for the sub-scales were as follows: MI intervention component (KR20=.7); stage-appropriate MI-based intervention (KR20=.55); MI spirit (KR20=.5); appropriate assessment (KR20=.45) and appropriate assisting (KR20=.56). CONCLUSIONS: The instrument demonstrated good inter-rater reliability and moderate overall internal consistency when used to assess performing brief behavioral change interventions by medical students. PRACTICE IMPLICATIONS: This practical instrument can be used with minimal training and demonstrates promising psychometric properties when evaluated with medical students counseling standardized patients. Further testing is required to evaluate its usefulness in clinical settings.

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BACKGROUND AND OBJECTIVES: There is little research on training medical students in smoking cessation counseling (SCC). This study aimed to determine if a personal digital assistant (PDA)-based SCC tool can improve medical student SCC. METHODS: We conducted a randomized, controlled trial with third-year medical students. SCC behaviors, comfort, and knowledge were assessed using a validated survey before students attended a workshop on SCC. Student groups were then randomized to receive a paper-based reminder tool or the reminder plus a PDA-based SCC tool. The validated survey was repeated upon clerkship completion, and a videotaped standardized patient interview was assessed by trained reviewers using a 24-item SCC checklist. Focus groups assessed satisfaction with the PDA tool, usability, and barriers to use. RESULTS: SCC behaviors, knowledge, and comfort increased among all participants, with no statistical differences between groups. The PDA tool group performed 62% of key SCC activities during the videotaped interview, while the control group performed 69%. Students reported discomfort using the PDA with patients, lack of time, and lack of training as barriers to use of the tool. CONCLUSIONS: We demonstrated improvement of SCC skills by third-year medical students using a workshop combined with a supplemental reference tool. However, a PDA-based tool did not increase key SCC behaviors compared with a paper-based reminder. For a PDA intervention to be effective in this setting, the tool must be simplified and additional training provided.

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Prediction of the rate of gas production from bioreactor landfills is important for the optimization of energy recovery and for estimating greenhouse gas emissions. To improve the predictability of gas production, landfill gas (LFG) composition and flow rates were monitored for 4 yr from one conventional and two bioreactor landfill cells at the Outer Loop Landfill in Louisville, KY. The ultimate methane yield (L(o)) was estimated from the biochemical methane (CH4) potential of freshly buried refuse and the decay rate constant (k) was estimated from measured CH4 collection. The site-specific L(o) was estimated to be 48.4 m3-CH4 wet Mg(-1). The estimated decay rate in the conventional cell (0.06 yr(-1)) was comparable to the AP-42 default value of 0.04 yr(-1), whereas estimates for the two bioreactor cells were substantially higher (approximately 0.11 yr(-1)). The data document the ability of the bioreactor operation to enhance landfill CH4 generation, although the estimated decay rate is sensitive to the selected L(o). The more rapid decomposition in the bioreactor cells reduces the length of time over which gas will be produced and emphasizes the importance of having a LFG collection system operational once the waste receives added moisture.

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Air addition has been proposed as a technique for rapid stabilization of municipal solid waste (MSW) in landfills. The objective of this study was to observe the change in concentration of trace constituents of landfill gas in response to air addition. Air injection tests were conducted at a MSW landfill in Florida, and the concentrations of several gaseous constituents at adjacent wells within the waste were measured. The concentrations of methane, carbon dioxide, and oxygen, as well as several trace constituents, were measured both prior to and during air addition. The trace components investigated included a suite of volatile organic compounds (VOCs), nitrous oxide (N20), carbon monoxide (CO), and hydrogen sulfide (H2S). A significant increase in CO was observed in 9 of 14 monitoring points; overall, CO concentrations were found to increase as the ratio of CH4 to CO2 decreased. A significant decrease in H2S was observed at 6 of 14 monitoring points. Air injection did not have a noticeable affect on VOC or N2O concentrations compared to initial levels.

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