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Methane emissions from solid waste may represent a substantial fraction of the global anthropogenic budget, but few comprehensive studies exist to assess inventory assumptions. We quantified emissions at hundreds of large landfills across 18 states in the United States between 2016 and 2022 using airborne imaging spectrometers. Spanning 20% of open United States landfills, this represents the most systematic measurement-based study of methane point sources of the waste sector. We detected significant point source emissions at a majority (52%) of these sites, many with emissions persisting over multiple revisits (weeks to years). We compared these against independent contemporaneous in situ airborne observations at 15 landfills and established good agreement. Our findings indicate a need for long-term, synoptic-scale monitoring of landfill emissions in the context of climate change mitigation policy. [ABSTRACT FROM AUTHOR]

• Collection efficiency estimates are necessary for accurate emissions modeling. • Measured collection efficiency data categorized and compared with current defaults. • Cover type was statistically significant indicator of collection efficiency. • Results: 41% efficiency for daily cover, 69 % for intermediate, and 71 % for final. • New defaults greatly reduce discrepancy between modeled and measured estimates. Landfill methane emissions are commonly estimated using cover-type dependent default collection efficiency values, with a first-order decay model or measured gas collection. Current default collection efficiencies used in the United States were predominately derived from 4 studies conducted during or prior to 2007 that relied on flux chambers. Flux chambers are limited by small sample sizes, placement restrictions, and the inability to measure emissions from gas or leachate collection systems. Since 2007, over 14 new studies have been completed using more advanced technologies that allow for direct measurement of methane plumes from most or all of a landfill's surface. On average, these measurements are 2–3 times greater than emissions predicted by current models and collection efficiency defaults. In lieu of measuring emissions from all landfills, updating collection efficiency defaults can bring modeled emissions into better alignment with measurements. To this end, collection efficiency estimates derived from measured data were categorized into cover types and then adjusted to account for cases where whole plume measurement was an amalgamation of multiple cover types. The resultant adjusted default values were 41% for daily cover, 69% for intermediate cover, and 71% for final cover. Direct measurement of landfill methane emissions is preferrable to account for the full range of variables driving landfill emissions, including collection system design and operation. However, applying these updated defaults back into the landfill emission models eliminates underprediction of landfill emissions for the dataset reviewed, and would provide a more accurate estimate of landfill gas emissions where measurements are unavailable. [ABSTRACT FROM AUTHOR]

[Display omitted] • C4-C7 PFCAs are predominant in leachate, while FOTHs are dominant in landfill air. • The quality of installed landfill liners is critical for minimizing PFAS leakage. • Activated carbon, ion exchange, and reverse osmosis are effective for treating PFAS in leachate. • Foam fractionation and advanced oxidation are effective per laboratory/pilot scale tests. • Key knowledge gaps in PFAS management at landfills are identified. Landfills have served as the final repository for > 50 % municipal solid wastes in the United States. Because of their widespread uses and persistence in the environment, per- and polyfluoroalkyl substances (PFAS) (>4000 on the global market) are ubiquitously present in everyday consumer, commercial and industrial products, and have been widely detected in both closed (tens ng/L) and active (thousands to ten thousands ng/L) landfills due to disposal of PFAS-containing materials. Along with the decomposition of wastes in-place, PFAS can be transformed and released from the wastes into leachate and landfill gas. Consequently, it is critical to understand the occurrence and transformation of PFAS in landfills and the effectiveness of landfills, as a disposal alternative, for long-term containment of PFAS. This article presents a state-of-the-art review on the occurrence and transformation of PFAS in landfills, and possible effect of PFAS on the integrity of modern liner systems. Based on the data published from 10 countries (250 + landfills), C4-C7 perfluoroalkyl carboxylic acids were found predominant in the untreated landfill leachate and neutral PFAS, primarily fluorotelomer alcohols, in landfill air. The effectiveness and limitations of the conventional leachate treatment technologies and emerging technologies were also evaluated to address PFAS released into the leachate. Among conventional technologies, reverse osmosis (RO) may achieve a high removal efficiency of 90–100 % based on full-scale data, which, however, is vulnerable to the organic fouling and requires additional disposal of the concentrate. Implications of these knowledge on PFAS management at landfills are discussed and major knowledge gaps are identified. [ABSTRACT FROM AUTHOR]

Managing municipal solid waste (MSW) presents many challenges, including the production of methane when MSW biodegrades in landfills. The search for methods to predict methane generation easily and accurately has been ongoing as MSW management improves and the damage presented by greenhouse gases is realized. To study MSW biodegradability, samples of solid waste were collected by sorting trash at four landfills and transfer stations in the southeast United States and transported to laboratories where the MSW was processed and analyzed for methane potential using biochemical methane potential assay, fiber content (lignin, cellulose, and hemicellulose), total carbon analysis, and elemental analysis. Searches for correlation between these data and methane generation revealed that average cellulose content correlated with methane generation potential (R2 = 0.90). A formula for predicting the methane potential of MSW samples using elemental analysis and 1 of 14 different correction factors, assigned by waste category type, is also presented. The methods presented in this work can help researchers and landfill operators better evaluate the methane potential of the MSW they work with. [ABSTRACT FROM AUTHOR]

• Textile waste generation does not occur evenly throughout Florida, United States. • Counties with higher incomes generated 95.7 lb of textile waste per person per year. • Counties with lower incomes generated only 54.7 lb of textile waste per person per year. • Textile recycling behavior was relatively even across areas. • Wealthier counties contribute more to the problem of textile waste. The amount of post-consumer textile waste (PCTW) generated annually in the United States has increased nearly ten-fold since the 1960s to exceed more than 34 billion pounds annually. Of the waste generated, 66% is sent to landfills, 19% is combusted with energy recovery, and only 15% is recycled. When left to decompose in landfills, PCTW decomposes, producing harmful leachates and greenhouse gases including methane. In this study, we used publicly available data from 67 counties in the state of Florida from 2014 to 2019 to assess how PCTW generation and recycling behaviors differ by area-level demographic, socioeconomic, and retail characteristics. We also used publicly available data on landfills to determine whether these same factors were associated with having more landfills per capita in a county. This study provides preliminary evidence that people living in areas with higher incomes, that are more racially segregated, and that have more clothing stores generate significantly more textile waste than people in other areas. In contrast, there were more landfills per capita in areas with lower incomes and fewer landfills per capita in areas that were more racially segregated. Textile recycling occurred at relatively uniform rates across counties. Taken together, these findings support the understanding that textile waste represents an issue of environmental injustice; wealthier communities contribute more PCTW to landfills, which are more commonly located in communities with lower socioeconomic status. Multipronged solutions are needed to produce relevant behavior change, including efforts and policies that seek to reduce textile consumption and increase textile recycling at the individual and societal level. [ABSTRACT FROM AUTHOR]

Featured Application: This research was designed to understand the effects of landfill soil gases on the events of subsurface landfill fires or elevated temperature which is experienced by many landfills during their operational and post-operational period. A framework proposed in this article can assist landfill authorities in controlling or preventing such hazardous incidents related to subsurface elevated thermal conditions. Subsurface temperature is a critical indicator for the identification of the risk associated with subsurface fire hazards in landfills. Most operational landfills in the United States (US) have experienced exothermic reactions in their subsurface. The subsurface landfill area is composed of various gases generated from chemical reactions inside the landfills. Federal laws in the US mandate the monitoring of gases in landfills to prevent hazardous events such as landfill fire breakouts. There are insufficient investigations conducted to identify the causes of landfill fire hazards. The objective of this research is to develop a methodological approach to this issue. In this study, the relationship was investigated between the subsurface elevated temperature (SET) and soil gases (i.e., methane, carbon dioxide, carbon monoxide, nitrogen, and oxygen) with the greatest influence in landfills. The significance level of the effect of soil gases on the SET was assessed using a decision tree approach. A naïve Bayes technique for conditional probability was implemented to investigate how different gas combinations can affect different temperature ranges with respect to the safe and unsafe states of these gases. The results indicate that methane and carbon dioxide gases are strongly associated with SETs. Among sixteen possible gas combinations, three were identified as the most probable predictors of SETs. A three-step risk assessment framework is proposed to identify the risk of landfill fire incidents. The key findings of this research could be beneficial to landfill authorities and better ensure the safety of the community health and environment. [ABSTRACT FROM AUTHOR]

The revised Renewable Fuel Standard's cellulosic biofuels mandate requires the USA to consume 16 000 million gallons of cellulosic biofuel per year by 2022. The cellulosic biofuels industry has fallen far short of reaching the production targets needed to achieve this volume, and it has even struggled to achieve the greatly reduced revised volumes that were created by the US Environmental Protection Agency despite the subsequent inclusion of landfill gas within the mandate. This article examines the underlying causes of this shortfall from the perspectives of markets and policy. It examines how the cellulosic biofuels production environment has not been conducive to the cost‐competitiveness of pioneer, first‐of‐their‐kind facilities and pathway buildout, and how recent techno‐economic analyses have used uncertainty to quantify the impacts of this environment. It further examines how the cellulosic biofuels mandate has actually hindered commercialization despite being intended to support it. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Globally, a whopping increase in solid waste (SW) generation and the risks posed by climate change are major concerns. A wide spread practice for disposal of municipal solid waste (MSW) is landfill, which swells with population and urbanization. Waste, if treated properly, can be used to produce renewable energy. The recent global event COP 27 mainly stressed on production of renewable energy to achieve the Net Zero target. The MSW landfill is the most significant anthropogenic source of methane (CH 4) emission. On one side, CH 4 is a greenhouse gas (GHG), and on the other it is a main component of biogas. Wastewater that collects due to rainwater percolation in landfills creates landfill leachate. There is a need to understand global landfill management practices thoroughly for implementation of better practices and policies related to this threat. This study critically reviews recent publications on leachate and landfill gas. The review discusses leachate treatment and landfill gas emissions, focusing on the possible reduction technology of CH 4 emission and its impact on the environment. Mixed leachate will benefit from the combinational therapy method because of its intricate combination. Implementation of circular material management, entrepreneurship ideas, blockchain, machine learning, LCA usage in waste management, and economic benefits from CH 4 production have been emphasized. Bibliometric analysis of 908 articles from the last 37 years revealed that industrialized nations dominate this research domain, with the United States having the highest number of citations. [Display omitted] • The most significant anthropogenic source of methane emission is landfill. • A combinational leachate treatment process is required due to its complex composition. • Circular material management approach will enhance entrepreneurship opportunities. [ABSTRACT FROM AUTHOR]

The article focuses on the landfill gas-to-energy (LFGE) projects in the U.S. and Great Britain. The article presents different approaches taken by these two nations in concern with the landfill gas emissions and tax based incentives for LFGE project. It also shows that Great Britain's approach is better in reducing biodegradable municipal solid waste.

The article focuses on greenhouse gas emissions coming from municipal solid waste facilities. In the authors' case study, they used four waste emissions quantification methods that include the Intergovernmental Panel on Climate Change and the U.S. Environmental Protection Agency Waste Reduction Model on greater Toronto, Ontario's waste disposal data. They discovered that the IPCC2006 method was the way to evaluate the effectivity of waste management programs.

The maximum contaminant level for arsenic was reduced by the U.S. Environmental Protection Agency (U.S. E.P.A.) for Drinking Water Standards from 50 micrograms per liter (µg/L) to 10 µg/L, effective January 23, 2006. The subject site is a double-lined sanitary landfill facility located in the mid-Atlantic region of the United States. Arsenic was reported above the maximum contaminant level in a downgradient monitoring well (MW-18) in July 2005. Since July 2005, arsenic levels in MW-18 fluctuated above and below 10 µg/L. This research focuses on determining whether reducing conditions in groundwater, enhanced by subsurface landfill gas emissions, were causing naturally-occurring arsenic to mobilize from the native variably-saturated vadose zone soils into groundwater. The groundwater data collected from the impacted well (MW-18) were compared to an upgradient well (MW-8) to determine whether significant differences existed during the time period of April 2004 to April 2007. Linear regression analysis was also used to determine whether other parameters had a significant relationship with the arsenic concentrations detected in MW-18. The groundwater located in MW-18 was consistently more reduced than groundwater located in the upgradient/background well MW-8, and this was most likely attributed to the presence of subsurface landfill gas in the area. According to the U.S. E.P.A., oxidation-reduction potential (ORP) values in groundwater less than 50 millivolts (mv) suggest that a reducing environment may be present. The data presented in this study indicate that arsenic can mobilize into groundwater under moderately reducing conditions, with ORP measurements averaging 53 mv. [ABSTRACT FROM AUTHOR]

This study provides observation-based national estimates of CFC-11, CFC-12, CFC-113, and 1,1,1-trichloroethane emissions for the United States (US) and United Kingdom (UK) from municipal solid waste (MSW) landfills. The scarcity of national estimates has lead to the assumption that a significant fraction of the lingering ozonedepleting substance (ODS) emissions, which have been detected in industrialized countries, could be emitted from landfills. Spatial coverage was achieved through sampling at seven landfills in Massachusetts and through data provided by nine UK landfills. Linear least square regressions of recovered ODS vs. CH4 were used in combination with national estimates of landfill CH4 emissions to estimate 2006 national US and UK ODS landfill emissions. The ODS landfill emission estimates were then compared to recent estimates of total US and UK ODS emissions. US ODS landfill emissions are 0.4%-1% (0.006-0.09 Gg/year) of total US emissions. UK ODS landfill emission estimates are 1% (0.008 Gg/year) and 6% (0.03 Gg/year) of total UK CFC-11 and CFC-12 emissions, respectively. This indicates that landfills are only a minor source of lingering ODS emissions in the US, but may be more significant for CFC-12 emissions in the UK. The implication is that the majority of current ODS emissions in industrialized countries is likely coming from equipment still in use. [ABSTRACT FROM AUTHOR]

The article focuses on the landfill gas-to-energy projects in the U.S. The discussion on solid waste landfills states that a huge percentage of solid waste generation was put in municipal waste landfills. The U.S. Environmental Protection Agency (EPA) reveals the unshakeable decrease of landfills in the country from 8,000 in 1988 to 1, 754 in 2006. It discusses the role of using LFG-to-energy project on the reduction of greenhouse gas emissions. Benefits of the gas-to-energy projects are also offered which include the reductions health risk and explosion hazards. It also offers information on methane, a key component of landfill gas, and its implications to climate-change. Summaries of several research articles related to the topic are also offered.

This report assesses gas-phase mass transfer processes in landfills with respect to their influence on waste biodegradation. Gas-phase transport must dominate in many regions of the waste because aqueous-phase transport is restricted, the environment is largely unsaturated, and substantial quantities of gas are produced. Analysis of landfill gas and landfill gas condensate at four municipal solid waste landfills in the eastern United States demonstrated that both volatile fatty acids and microorganisms are transported in the gas phase. The heterogeneity, mass transfer limitations, and significant thermal gradients in waste environments imply that gas-phase processes can play crucial roles in waste decomposition, for example by regulating local pH and distributing trace nutrients. A conceptual framework describing these processes is presented. Implications for waste management, landfill design, energy production, air emissions, and anaerobic microbiology are discussed. [ABSTRACT FROM AUTHOR]

This study evaluated the potential impact of carbon dioxide contained in municipal solid waste (MSW) landfill gas on the release of cadmium from uncontaminated native soils. The study was initiated to evaluate the potential sources of elevated cadmium concentrations detected in monitoring wells downgradient of the landfill but not in landfill leachate or monitoring wells upgradient. The study included field data evaluation, soil leaching experiments, and geochemical modeling using MINEQL+ and Visual MINTEQ chemical speciation software. Bench-scale leaching experiments were conducted using uncontaminated soils with natural cadmium concentrations ranging from less than 0.10 to 2.6 mg/kg. Carbon dioxide gas was equilibrated with uncontaminated soil samples and ground water from the site to simulate field conditions. Carbon dioxide concentrations were varied from 10% to 100%. Dissolved cadmium concentrations measured over this range of carbon dioxide concentration increased from less than 0.0001 to 0.0047 mg/L, which is equivalent to the maximum contaminant level of 0.005 mg/L for cadmium (U.S. EPA). Geochemical equilibrium modeling using Visual MINTEQ demonstrated that cadmium carbonate, or otavite, is the primary cadmium mineral controlling cadmium solubility. Predicted dissolved cadmium concentrations ranged from 0.0221 to 0.664 mg/L, with carbon dioxide concentrations of 0.0316% (atmospheric concentration) to 100%. MINEQL+ sorption modeling using a surrogate soil system predicted that dissolved cadmium concentrations would increase from 0.00603 to 0.0737 mg/L, which is in the range of cadmium concentrations observed in field samples. In response to these findings, the landfill operator initiated soil vapor extraction (SVE) in the vadose zone around the impacted wells. Since startup of the SVE system, dissolved cadmium concentrations in the formerly impacted wells have decreased to below the method detection limits. [ABSTRACT FROM AUTHOR]

Landfill gas collection data from wet landfill cells were analyzed and first-order gas generation model parameters were estimated for the US EPA landfill gas emissions model (LandGEM). Parameters were determined through statistical comparison of predicted and actual gas collection. The US EPA LandGEM model appeared to fit the data well, provided it is preceded by a lag phase, which on average was 1.5 years. The first-order reaction rate constant, k, and the methane generation potential, L o, were estimated for a set of landfills with short-term waste placement and long-term gas collection data. Mean and 95% confidence parameter estimates for these data sets were found using mixed-effects model regression followed by bootstrap analysis. The mean values for the specific methane volume produced during the lag phase (V sto), L o, and k were 33m3/Megagrams (Mg), 76m3/Mg, and 0.28year−1, respectively. Parameters were also estimated for three full scale wet landfills where waste was placed over many years. The k and L o estimated for these landfills were 0.21year−1, 115m3/Mg, 0.11year−1, 95m3/Mg, and 0.12year−1 and 87m3/Mg, respectively. A group of data points from wet landfills cells with short-term data were also analyzed. A conservative set of parameter estimates was suggested based on the upper 95% confidence interval parameters as a k of 0.3year−1 and a L o of 100m3/Mg if design is optimized and the lag is minimized. [Copyright &y& Elsevier]

This article discusses the U.S. Environmental Protection Agency's Landfill Methane Outreach Program. Municipal solid waste landfills are the largest source of human-related methane emissions in the United States. Instead of allowing LFG to escape into the air, it can be captured, converted, and used as an energy source. The Landfill Methane Outreach Program is a voluntary assistance program that helps to reduce methane emissions from landfills by encouraging the recovery and use of landfill gas as an energy resource. The article discusses several different types of landfill gas utilization projects. It also discusses market drivers, environmental benefits, and financial benefits. The article concludes with a discussion on the future of landfill gas energy projects. [ABSTRACT FROM AUTHOR]

Methane emissions from municipal landfills represent 3% of the total United States greenhouse gas emissions that contribute to climate change. These methane emissions can be released to the air or collected and flared. This landfill gas also has the potential to be used to generate electricity. In 1994, the Environmental Protection Agency (EPA) created the Landfill Methane Outreach Program, with the objective of promoting the development of landfill-gas- to-energy projects around the country. There are currently 2,300 active landfills in the United States. Although there are already 382 operational projects, there are many more landfills with the potential to use the gas. EPA has identified at least 630 candidate landfills for energy projects, and many more have still not been identified. The objective of this paper is to evaluate total private and social benefits of landfill-gas-to-energy projects, taking into consideration not only the costs of installing and maintaining the necessary equipment and the revenues obtained from selling the electricity but also a valuation of the greenhouse gas emissions that would be prevented and the emissions of criteria pollutants created by the electricity generating equipment. It also evaluates the break-even government subsidies that would be required to make such projects economically viable from private and social perspectives in comparison to current subsidies. it was found that the private breakeven price of electricity for these projects is lower than $0.04/kWh. Moreover, the optimum social subsidy was found to be less than $0.0085/ kWh, which is about 40% lower than the currently available federal tax break of $0.015/kWh. The method developed for this paper can be applied to other renewable energy technologies, to show their relative social costs and benefits. [ABSTRACT FROM AUTHOR]

The feasibility of using landfill gas (LFG) for electricity generation at four St. Louis, Mo., area landfills was explored using the U.S. EPA's E-PLUS (Energy Project Landfill Gas Utilization Software). The estimated break-even generation price of the electricity was about 4;ct/kW·h. This price is higher than the current avoided cost provided by utilities. These results are consistent with the current situation for the entire renewable energy industry. Renewable technologies, in general, are characterized by relatively high capital costs and low operation and maintenance costs, and with the development of electricity deregulation throughout the United States, renewable energy is facing more competitive challenges. With the loss of federal tax incentives and relatively low electricity prices, fewer LFG-to-electricity projects are being implemented. LFG-to-energy facilities may be able to take advantage of increasing demands for green energy and markets for greenhouse gas emission reductions, but to make LFG projects economically feasible, it appears that some type of subsidy will be necessary to take into account the pollution reduction benefits derived from utilizing LFG. [ABSTRACT FROM AUTHOR]

Landfill gas produces ozone precursors such as nitrogen oxides and formaldehyde when combusted in flares or stationary engines. Solid waste landfills are also the third largest anthropogenic source of methane in the United States. Methane is both a greenhouse gas and a tropospheric ozone precursor. Despite its low photochemical reactivity, methane may noticeably affect urban ozone if released in large quantities along with other organic compounds in landfill gas. A fine-scale 3D Eulerian chemical transport model was used to demonstrate that, under meteorological and background chemical conditions conducive to high ozone concentrations, typical emissions of ozone precursors from a single hypothetical landfill may result in persistent daytime additions to ozone of over 1 part per billion (ppb) by volume tens of kilometers downwind. Large leaks of landfill gas can enhance this ozone pollution by over a tenth of a ppb, and external sources of non-methane ozone precursors may further exacerbate this impact. In addition, landfill gas combustion may increase near-source exposure to toxic formaldehyde by well over half a ppb. In Southeast Michigan, the combined influence of several landfills upwind of key monitoring sites may contribute significantly to observed exceedances of the U.S. ozone standard. [ABSTRACT FROM AUTHOR]

Studies the methane emissions at nine United States landfill sites using chamber and tracer flux techniques. Values of methane emissions; Calculation of emission factors; Evaluation of the effectiveness of landfill gas recovery efforts.

Focuses on the construction of a site of a landfill for radium waste by the US Radium Corp., a manufacturer of luminescent watch dials with radium-based paint in Montclair, New Jersey. Health hazards of radon gas; Move of the Department of Environmental Protection Agency in protecting the citizens from the gas exposure; Amount allocated for the environmental protection program.

Focuses on the advantage of the Section 29 tax credits to gas producers in the U.S. Development of tax credits on fuels from older coal-seam gas projects; Need for the government to establish the unrelated-party sale rule for alternative fuels; Expectation for landfill gas projects to produce an economic profit.