ABSTRACT
The early stages of municipal solid waste degradation in landfills are complex harmonies of physical, biological, and chemical interactions that all work in concert to degrade trash into smaller and more stable materials. While many approaches have been taken to understand parts of this process, this new work attempted to simulate the early stages of landfills in controlled laboratory environments while observing the impacts of food waste content at different concentrations. This was completed by operating landfill lysimeters in a laboratory for approximately 1000 days, simulating landfill interior conditions while measuring the gas and liquid byproducts to study the impact of food waste presence in these environments. Metagenomic analysis after the experiment identified over 18,000 individual species and allowed comparison with past studies while also surveying microorganisms present in landfills. Similar populations found in past studies suggested the current experiments successfully replicated landfill conditions. While food waste diversion had a discernable impact on gas production, it did not show a clear and consistent impact on the microbiomes identified in this study.
Subject(s)
Refuse Disposal , Methane/analysis , Food , Solid Waste/analysis , Waste Disposal FacilitiesABSTRACT
Remote locations, small communities, and weather prohibit the operation of piped sanitary sewers in many Alaska Native Villages (ANVs). Research was conducted to understand the technical feasibility of installing anaerobic digesters (ADs) in remote ANVs which would be heated by solar thermal collectors. Biochemical methane potential (BMP) assays were conducted to understand the effect of freezing and thawing on methanogenic activity of synthetic human feces. BMPs were frozen at -20 or -80 °C for 7 days and then incubated at psychrophilic (20 °C) or mesophilic (37 °C) conditions. Psychrophilic BMPs frozen at -20 or -80 °C yielded 453 ± 119 and 662 ± 77 mL CH4/g VS, respectively. Mesophilic BMPs frozen at -20 or -80 °C yielded 337 ± 59 and 495 ± 63 mL CH4/g VS, respectively. Freezing caused a lag period, but ultimately many of the assays reached yields similar to or even greater than the baseline, unfrozen assays. Monthly solar radiation and air temperature data were used to identify the number of solar thermal collectors that would be required to supplement heat energy to operate the ADs in several locations. Alaskan subarctic locations receive enough solar thermal energy in summer months to support seasonally operated, psychrophilic ADs.
ABSTRACT
Water above 374 °C and 22.1 MPa, becomes supercritical, a special state where organic solubility increases and oxidation processes are accelerated. Supercritical water oxidation (SCWO) has been previously shown to destroy hazardous substances such as halogenated compounds. Three separate providers of SCWO technology were contracted to test the efficacy of SCWO systems to reduce per- and poly-fluoroalkyl substances (PFAS) concentrations from solutions of dilute aqueous film-forming foam (AFFF). The findings of all three demonstration studies, showed greater than 99% reduction of the total PFAS identified in a targeted-compound analysis, including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). PFOS was reduced from 26.2 mg/L to 240 µg/L, 30.4 mg/L to 0.310 µg/L, and 190 mg/L to 8.57 µg/L, from the Aquarden, Battelle, and 374Water demonstrations, respectively. Similarly, PFOA was reduced from 930 to 0.14 µg/L, 883 to 0.102 µg/L, and 3,100 µg/L to non-detect in the three evaluations. Additionally, chemical oxygen demand of the dilute AFFF was shown to reduce from 4,750 to 5.17 mg/L after treatment, indicating significant organic compound destruction. In one demonstration, a mass balance of the influent and effluent found that the targeted compounds accounted for only 27% of the generated fluoride, suggesting that more PFAS were destroyed than measured and emphasizing the limitations of targeted analysis alone. As a destructive technology, SCWO may be an alternative to incineration and could be a permanent solution for PFAS-laden wastewaters rather than disposal by injection into a deep-well or landfilling. Additional investigation of reaction by-products remains to be conducted for a complete assessment of SCWO's potential as a safe and effective PFAS treatment technology.
ABSTRACT
The Intergovernmental Panel on Climate Change (IPCC) protocol for predicting national methane emission inventories from landfills was published 22 years ago in the 1996 Revised Guidelines. There currently exists a broad dataset to review landfill parameters and reported values and their appropriateness in use and application in a range of site-specific, regional, and national estimates. Degradable organic carbon (DOC) content was found to range from 0.0105 to 0.65 g C/g waste, with an average of 0.166 g C/g waste. The fraction of DOC that would anaerobically degrade (DOC f) was reported to range from 50-83%, whereas higher and lower values have been experimentally determined for a variety of waste components, such as wood (0-50%) and food waste (50-75%). Where field validation occurred for the methane correction factor, values were substantially lower than defaults. The fraction of methane in anaerobic landfill gas ( F) default of 50% is almost universally applied and is appropriate for cellulosic wastes. The methane generation rate constant ( k) varied widely from 0.01 to 0.51 y-1, representing half-lives from 1 to 69 years. Methane oxidation (OX) default values of 0 and 10% may be valid, but values greater than 30% have been reported for porous covers at managed sites. The IPCC protocol is a practical tool with uncertainties and limitations that must be addressed when used for purposes other than developing inventories.
Subject(s)
Air Pollutants , Refuse Disposal , Climate Change , Methane , Waste Disposal Facilities , WoodABSTRACT
Recently, gypsum drywall products imported to the United States (US) were found to cause metal corrosion and tarnishing in some homes, often necessitating that this drywall be discarded. Research assessed the potential implications of recycling and landfilling corrosive/imported drywall. Samples of corrosive drywall were collected from homes in Florida, US and these characteristics were assessed relative to domestically-produced drywall purchased from retail outlets. The total and synthetic precipitation leaching procedure (SPLP) leachable heavy metal concentrations were measured and compared to risk-based regulatory thresholds to assess the possible land application risk. In a majority of samples, concentrations were below levels of regulatory concern. The mean concentration of several elements exceeded the thresholds in a few samples for the direct exposure assessment (As) and the groundwater leaching assessment (Al, B, Hg, Mn, Sr and V); but the results did not suggest that corrosive drywall would present a greater risk than domestic drywall. To assess landfilling concerns, the potential for sulfur gases emissions upon disposal was evaluated. Experiments indicated that corrosive drywall would not pose a greater risk of long-term H2S emissions compared to domestic drywall.
Subject(s)
Air Pollutants/chemistry , Construction Materials , Corrosion , Recycling , Sulfur/chemistry , Environmental Monitoring , Florida , HumansABSTRACT
As part of its commitment to the United Nations Framework Convention on Climate Change, the U.S. annually develops a national estimate of methane emissions from municipal solid waste (MSW) landfills by aggregating activity data from each facility. Since 2010, the U.S. has reported a 20 % decrease in MSW landfill emissions despite a 21 % increase in tons disposed. Operator-submitted data were investigated to understand the causes of this decline. In the U.S., operators of landfills with a gas collection and control system (GCCS) calculate their facility's emissions via two separate approaches - (1) first-order decay (FOD) and (2) collection efficiency assumption (CEA) - and select either result to feed into the annual inventory. The FOD model predicts methane generation proportional to waste disposal and that approach calculated a 19 % increase in total methane generated from 2010 to 2022, whereas generation via the CEA approach decreased by 8.9 %. The amount of measured methane collected has increased 7.5 % for the same years. Discrepancies between the two models' generated methane, assumed gas collection efficiencies, and oxidized methane compound into substantive differences in national estimates. Operators more frequently select the CEA method, which results in decreased national estimates. If only the FOD method was used, U.S. MSW landfill emissions would be 1.3-1.7 times greater than current estimates which is similar to recent extrapolations from remote sensing campaigns in the U.S. Both models contain parameters with large inherent uncertainty. Without measurement methods that continuously quantify both point-source and diffuse emissions, an assessment of either equation's accuracy cannot be made.
Subject(s)
Air Pollutants , Methane , Models, Theoretical , Refuse Disposal , Waste Disposal Facilities , Methane/analysis , United States , Air Pollutants/analysis , Refuse Disposal/methods , Greenhouse Gases/analysis , Environmental Monitoring/methods , Solid Waste/analysisABSTRACT
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
Elevated temperature landfills (ETLFs) are municipal solid waste (MSW) landfills that have been impacted by subsurface exothermic reactions (SERs) and display unusual gas and leachate composition. Leachate quantity and quality data were analyzed to identify indicators of a SER at an ETLF in Ohio, USA. ETLF leachate generation increased from 2.04 to 14.4 m3/hectare-day (218 to 1,539 gallons/acre-day), peaking 16 months after the reaction was first noticed. The leachate generation rate for this ETLF remains about two times greater than the average Ohio MSW landfill. Several general parameters such as pH, electrical conductivity (EC), and total dissolved solids (TDS) remain impacted 5 years later. Similarly, metals such as arsenic, iron, calcium, potassium, and magnesium have increased in concentration. Volatile organic compounds (VOCs) behavior was less consistent as a group of chemicals. Increases of VOCs such as acetone, benzene, and methyl ethyl ketone (MEK) also increased. Importantly, in one year, benzene exceeded its toxicity characteristic threshold meaning the leachate was a hazardous waste, substantially increasing treatment and disposal costs. It is not clear if the VOCs are produced directly by the SER or if they are an indicator that microbial processes -which would otherwise consume them- have been disrupted. ETLFs likely do not all undergo the same exothermic reaction(s) and, unlike the analysis of landfill gas composition, temporal changes in leachate constituents' concentrations may be more important than comparing to absolute values.
ABSTRACT
This data brief presents leachate disposal and management data for 43 active or closed municipal solid waste (MSW) landfills and planar surface areas for 40 of those landfills in Ohio, USA. Data were extracted from publicly available Annual Operational Reports from the Ohio Environmental Protection Agency (Ohio EPA) and consolidated into a digital dataset of two delimited text files. A total of 9,985 data points represent monthly leachate disposal totals, arranged by management type and by landfill. Leachate management data for some landfills extend from 1988-2020 but are mostly limited to 2010-2020. Annual planar surface areas were identified from topographic maps in the annual reports. A total of 610 data points were created for the annual surface area dataset. This dataset aggregates and organizes the information, allowing for accessibility and increased application to engineering analysis and research projects.
ABSTRACT
Landfill gas (LFG) wellhead data were compared to understand the range of observations due to unique conditions at five elevated temperature landfills (ETLFs) in the U.S. Correlations of the primary gas ratio, CH4:CO2, show distinct compositional indicators for (1) typical operation, (2) subsurface exothermic reactions (SERs), (3) high moisture content, and (4) air intrusion that can help operators and regulators diagnose conditions across gas extraction wells. ETLFs A, B, D, and E showed similar trends, such as decreasing CH4 and increasing CO2, CO, and H2 that have been previously described. ETLF C uniquely exhibited elevated CH4 and temperatures simultaneously due to carbonation (i.e., CO2 consumption) of a steel slag which was used as alternative daily cover (ADC). At the maximum gas well temperature, T = 82 °C/180 °F, CH4 and CO2 concentrations were 47% and 28%, respectively. At ETLFs A, B, and E, H2 > 50% were regularly observed in affected gas wells for several years. At the five ETLFs, maximum CO concentrations ranged from 1400-16,000 ppmv. Like the analysis of CH4:CO2, it is hypothesized here that H2 (%):CO (ppmv) may infer the types of waste that are thermally degrading. Co-disposal of industrial wastes and MSW and the use of potentially reactive ADCs should remain an important consideration for landfill operators and regulators because of their potential long-term impacts to LFG quality.
Subject(s)
Carbon Dioxide , Refuse Disposal , Carbon Dioxide/analysis , Temperature , Waste Disposal Facilities , Industrial Waste/analysis , Steel , Methane/analysisABSTRACT
The release of persistent per- and polyfluoroalkyl substances (PFAS) into the environment is a major concern for the United States Environmental Protection Agency (U.S. EPA). To complement its ongoing research efforts addressing PFAS contamination, the U.S. EPA's Office of Research and Development (ORD) commissioned the PFAS Innovative Treatment Team (PITT) to provide new perspectives on treatment and disposal of high priority PFAS-containing wastes. During its six-month tenure, the team was charged with identifying and developing promising solutions to destroy PFAS. The PITT examined emerging technologies for PFAS waste treatment and selected four technologies for further investigation. These technologies included mechanochemical treatment, electrochemical oxidation, gasification and pyrolysis, and supercritical water oxidation. This paper highlights these four technologies and discusses their prospects and the development needed before potentially becoming available solutions to address PFAS-contaminated waste.Implications: This paper examines four novel, non-combustion technologies or applications for the treatment of persistent per- and polyfluoroalkyl substances (PFAS) wastes. These technologies are introduced to the reader along with their current state of development and areas for further development. This information will be useful for developers, policy makers, and facility managers that are facing increasing issues with disposal of PFAS wastes.
Subject(s)
Fluorocarbons , Water Pollutants, Chemical , Fluorocarbons/analysis , United States , United States Environmental Protection Agency , Water Pollutants, Chemical/analysisABSTRACT
Methane generation potential, L0, 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 L0, which has been in place for almost 20â¯years, is 100â¯m3 CH4/Mg MSW as-discarded. Recent research suggests the yield of landfilled waste could be less than 60â¯m3 CH4/Mg MSW. This study aimed to measure the L0 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 L0 values for each waste load. An average value of 80â¯m3 CH4/Mg MSW was determined for all samples with 95% of values in the interval 74-86â¯m3 CH4/Mg MSW as-discarded. While no statistically significant difference was observed, commercial MSW yields (mean 85, median 88â¯m3 CH4/Mg MSW) showed a higher average L0 than residential MSW (mean 75, median 71â¯m3 CH4/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.
Subject(s)
Methane/analysis , Solid Waste , Waste Disposal Facilities , Refuse Disposal , United StatesABSTRACT
The effects of temperature and substrate size on the biochemical methane potential (BMP) assay were tested using eight municipal solid waste components. Two sample sizes were tested; size-reduced particles (xâ¯<â¯2â¯mm) which are typically used for BMP assays and unground samples (xâ¯>â¯20-100â¯mm) more similar to an as-disposed condition. Two incubation temperatures (35 and 55⯰C) were tested for each component. BMPs for office paper, newspaper, paperboard, and coated paper displayed little difference with regards to temperature or particle size. Mesophilic corrugated cardboard BMPs were significantly greater than their thermophilic counterparts. Hardwood, softwood, and cotton BMPs varied with particle size and temperature. Particle size reduction may increase the bioavailable carbon compounds for wood, but this step was not necessary to achieve similar methane yields for paper products. Extrapolating BMP results to predict landfill methane generation may have greater uncertainty for wood wastes and cotton textiles than paper products.
Subject(s)
Methane , Refuse Disposal , Solid Waste , Anaerobiosis , Particle Size , TemperatureABSTRACT
Landfill gas (LFG) generation is predicted by a first-order decay (FOD) equation that incorporates two parameters: a methane generation potential (L0) 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 (kc) 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.
Subject(s)
Air Pollutants/analysis , Environmental Monitoring/methods , Methane/analysis , Solid Waste/analysis , Waste Disposal Facilities , Australia , Models, Theoretical , Refuse DisposalABSTRACT
The potential for disposable electronic cigarettes (e-cigarettes) to be classified as hazardous waste was investigated. The Toxicity Characteristic Leaching Procedure (TCLP) was performed on 23 disposable e-cigarettes in a preliminary survey of metal leaching. Based on these results, four e-cigarette products were selected for replicate analysis by TCLP and the California Waste Extraction Test (WET). Lead was measured in leachate as high as 50mg/L by WET and 40mg/L by TCLP. Regulatory thresholds were exceeded by two of 15 products tested in total. Therefore, some e-cigarettes would be toxicity characteristic (TC) hazardous waste but a majority would not. When disposed in the unused form, e-cigarettes containing nicotine juice would be commercial chemical products (CCP) and would, in the United States (US), be considered a listed hazardous waste (P075). While household waste is exempt from hazardous waste regulation, there are many instances in which such waste would be subject to regulation. Manufactures and retailers with unused or expired e-cigarettes or nicotine juice solution would be required to manage these as hazardous waste upon disposal. Current regulations and policies regarding the availability of nicotine-containing e-cigarettes worldwide were reviewed. Despite their small size, disposable e-cigarettes are consumed and discarded much more quickly than typical electronics, which may become a growing concern for waste managers.