Article

# The greenhouse effect and US landfill methane

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## Abstract

The author estimates likely greenhouse contributions of methane emissions from solid waste landfills in the USA. These emissions appear significant: their effect, evaluated over the short term (< 10 years), is to add the order of 1 % to the total annual Increase of radiative forcing due to build-up of all green-house gases in Earth's atmosphere. Costs to mitigate landfill methane emissions were also estimated. Such costs appear quite low compared to those of most carbon dioxide mitigation approaches giving comparable benefit. This work, while preliminary, suggests landfill methane abatement is one of the more cost-effective measures that can be taken to address a component of the greenhouse problem.

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... Methane is a powerful greenhouse gas (GHG), with a global warming potential 28 times greater than CO 2 , on a 100-year timeframe (Myhre et al., 2013). Different organic materials have varying decay profiles, with easily digestible materials such as food waste typically fully decaying quickly, whereas decay of ligno-cellulosic materials such as wood products is limited and slow (Augenstein 1992). Understanding the contribution of individual organic components of the waste stream to landfill gas generation due to the extent of decay is important to more accurately estimate GHG emissions from landfills. ...
... Finally we make recommendations for future research. Augenstein, D. 1992 Commercial and industrial (C&I) waste-waste generated by business and industry, for example, shopping centres, office blocks or manufacturing plants. The most common materials in this waste stream are food, paper and cardboard and wood and wood waste.. ...
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Approximately 3.1 Mt of forest products are discarded in Australian landfills annually, with only limited knowledge on the extent of decay for the various products. As organic materials decay in landfills they release methane and carbon dioxide. The main aim of this study was to improve understanding of the extent of decomposition of wood and paper products in landfills in Australia, based on the analysis of carbon dynamics in forest products excavated from landfills in New South Wales and Queensland, and investigations of the fate of carbon in forest products under controlled laboratory conditions designed to optimise anaerobic decay. There was typically little or no decay in the wood samples from the landfills in Sydney. Although there was significant decay in rainforest wood excavated from Cairns, decay levels for other wood types found both in Cairns and Sydney landfills were lower (0.7-9.0%). Climate did not influence decay in wood and engineered wood products (EWP). Microscopic analyses revealed that most decay patterns in wood analysed from Sydney MSW landfill were consistent with aerobic fungal decay. Estimated carbon loss ranged from 0.6 to 9.0% for EWPs and 0 to 58.9% for paper. Papers produced from mechanical pulp had lower carbon loss than those produced via chemical processes. Climate impacted on decay levels for papers made from chemical pulp. Lower carbon losses were observed for EWP and paper excavated from the C&D landfill compared with MSW landfills. Decay factors for paper should therefore reflect pulp type, climate and landfill type. Carbon losses ranged from 0.2-3.8% for wood species tested in the reactor studies. The suggested factor for carbon loss for wood in landfills in Australia is 1.4%. Microscopy analyses in the wood revealed evidence of bacterial attack only. Addition of copy paper did not increase carbon loss for the wood species tested. Carbon losses for particleboard and MDF ranged from 0.7-1.6%. Carbon losses for bamboo (11.4%) were significantly higher than for EWPs. Carbon losses for the three types of copy paper ranged from 72.4 – to 82.5 %, and were significantly higher than for cardboard (43.8%). Differences in carbon loss between paper types were statistically significant. A decay factor for combined EWPs and wood in landfills in Australia of 1.3% and for paper products of 47.7% is proposed. The new suggested decay factors represent a significant reduction from factors currently used for forest products, with substantial impacts on greenhouse gas estimation from landfills.
... The design of biogas extraction systems is one of the most important elements for good management of large sanitary landfills. Uncontrolled biogas migration may cause sudden explosions (Christensen et al., 1995;Kocasoy and Curi, 1995), and landfill methane may contribute to the greenhouse effect (Augenstein, 1992;Lagerkvist, 1995;Pipatti and Savolainen, 1996;Winiwarter and Rypdal, 2001). Landfill gas extraction is also important for potential economic benefits. ...
Article
This manuscript proposes a practical methodology for estimating the operational vacuum for landfill biogas extraction from municipal landfills. The procedure is based on two sub-models which simulate landfill gas production from organic waste decomposition and distribution of gas pressure and gas movement induced by suction at a blower station. The two models are coupled in a single mass balance equation, obtaining a relationship between the operational vacuum and the amount of landfill gas that can be extracted from an assigned system of vertical wells. To better illustrate the procedure, it is applied to a case study, where a good agreement between simulated and measured data, within +/- 30%, is obtained.
... (For a discussion of this greenhouse cost effectiveness see Nordhaus, 1991. For one discussion of greenhouse cost effectiveness of landfill gas recovery see Augenstein, 1992) Landfill gas energy use also represents conservation of an energy resource otherwise normally wasted, and can contribute rather significantly to US and other nations' energy security: Present failure to u se methane (including flaring of collected methane, and uncollected methane fugitive to the atmosphere) represents a not-inconsiderable loss of fuel, even now equivalent to over 150,000 barrels of oil a day for the US. In alternate terms of electric generation, unexploited electric generation potential in the US can be estimated even now at between 4 and 7 GWe. ...
Article
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An advanced landfill bioreactor approach termed "controlled landfilling" is continuing development at the Central Landfill, in Yolo County, California. Two test cells have operated at Yolo at a scale of 9,000 tons since 1994. Operations have recently started at fullscale in cells with a total of over 100,000 tons of waste. Expected benefits to waste managers include maximum methane energy recovery and substantial early waste volume reduction, with associated potentials for landfill life extension and more capacity. Expected environmental benefits include earlier waste stabilization and minimization of landfill-gas related emissions. Methane generation and waste stabilization have been accelerated in a 9,000 ton test cell through managed additions of supplemental water and leachate. The first-order rate constant for methanogenesis has been over 0.4 year-1, over fivefold "normal" for a waste mass of this size. A control cell has been operated in parallel. Methane capture is maximized, with emissions minimized, by surface membrane overlying a surface permeable layer operated at slight vacuum to conduct gas to collection. Cells have been intensively instrumented to determine performance. Corresponding to solids' reduction to gas, there has been rapid waste volume reduction in the enhanced cell. Slow and controllable liquid additions have been successful in achieving good measured moisture distribution as well as the rapid waste decomposition. A scaled- up anaerobic bioreactor of 70,000 tons has been started and is in early monitoring. Details, and results obtained since 1994, are presented below.
... However, they can have a negative impact on the environment. For instance, wastes disposed of in landfills are sources of methane emissions [7][8][9][10][11], and life-cycle assessments indicate that incineration for energy recovery can have variable impacts on the climate depending on the waste composition [12]. Additionally, the suitability of alternative recovery methods, i.e., pyrolysis, liquefaction, gasification, and biomethanation, is dependent on the composition of MSW [13]. ...
Article
Accurate estimation of municipal solid waste (MSW) composition is critical for efficient waste management. In the United States, site-specific and material flow approaches determine the MSW composition at regional and national levels. The material flow-based national estimates are determined by the U.S. EPA; the U.S. EPA’s estimates are known to differ substantially from the aggregated tonnage of MSW managed by waste handling facilities in the United States. However, the material class-specific discrepancies of the U.S. EPA’s material flow approach resulting in these differences are unknown. To find the basis of these discrepancies, we analyze the discarded MSW stream of 27 U.S. states, which roughly accounts for 73 percent of the U.S. population. Our analysis indicates that the material flow-based national estimates are accurate for the food, plastic, and glass material classes. In contrast, we find that the U.S. EPA’s material flow-based predictions underestimate paper waste disposal by at least 15 million tons annually. These differences likely stem from incorrect assumptions of residence time. These results highlight the material class-specific strengths and drawbacks of the U.S. EPA’s material flow-based MSW estimates.
... According to a number of studies such as Komakech Augenstein (1992), stated that municipal solid waste, food waste inclusive is naturally degraded overtime in landfills producing green-house gases, odour, and ground water pollution. The high organic content and moisture content in the organic waste (fruit, food and vegetable waste inclusive) can be utilized for generation of biogas in anaerobic digestion process (Romero and Pe, 2008;Velmurugan and Ramanujam, 2011). ...
Article
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Small scale food processing is characteristic of many enterprises in Uganda. As such, the Food Technology Business Incubation Centre (FTBIC), at Makerere University offers food processing entrepreneurs an opportunity to learn practical skills that are indispensable in food processing value chains. Despite the good intensions, FTBIC organic waste, is a menace and a source of pests. The main goal of this study was to determine the most appropriate and optimum ratios of organic wastes for production of biogas to be converted to meet heating needs of FTBIC. The samples of organic waste were quantified and characterized for their potential to generate biogas. Nine treatments in duplicate without inoculum were selected for production of biogas in the ratios: pineapples and other waste 3:1 (A1), 1:1 (A2), and 1:3 (A3); Mangoes and other wastes 3:1 (B1), 1:1 (B2), and 1:3 (B3); and orange and other wastes 3:1 (C1), 1:1 (C2) and 1:3 (C3). Other wastes included: Irish potatoes, bananas, vegetables, passion fruits water melon, pumpkins, pawpaw, mixed food leftovers and jackfruit. The food/microorganism (F/M) ratio was 0.5 i.e. 1.5 gVS of the substrate was digested with 3 gVS of inoculum. On average, 213.7 kg of organic waste was produced daily from the processing unit. The moisture content (MC), total solids (TS), and volatile solids (VS) for the individual organic wastes ranged from 45 to 97.3% wet basis, 54.4 to 6.3% and 60 to 97.3% respectively. The MC, TS and VS of the treatments ranged from 80.8 to 89.2% wet basis, 10.8 to 19.2 gTS/kg and 923.2 to 952.7 gVS/kg respectively. Orange waste with other waste in the ratio of 3:1 yielded the best performance of food waste for biogas production (0.7 L/gVS). Thus more percentage of orange waste in a mixture of organic waste yielded the highest quantity of biogas.
... Emissions of methane and carbon dioxide from landfill surfaces contribute significantly to global warming or the greenhouse effect. Methane has received recent attention as a contributor to global warming because on a molecular basis, it has a relative effect 20 to 25 times greater than carbon dioxide (Lagerkvist, 1987;Blake and Rowland, 1988;Augenstein, 1990), it is more effective at trapping infrared radiation (Bingemer and Crutzen, 1987) and tends to persist longer in the atmosphere owing to other species (i.e. carbon monoxide) with a greater affinity for hydroxyl ions, the oxidizing agent for methane (Dickenson and Cicerone, 1986;. ...
Article
Inevitable consequences of the practice of solid waste disposal in landfills are gas and leachate generation due primarily to microbial decomposition, climatic conditions, refuse characteristics and landfilling operations. The migration of gas and leachate away from the landfill boundaries and their release into the surrounding environment present serious environmental concerns at both existing and new facilities. Besides potential health hazards, these concerns include, and are not limited to, fires and explosions, vegetation damage, unpleasant odors, landfill settlement, ground water pollution, air pollution and global warming. This paper presents an overview of gas and leachate formation mechanisms in landfills and their adverse environmental impacts, and describes control methods to eliminate or minimize these impacts.
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Hydrogen sulfide (H2S) has been identified as a principal odorous component of gaseous emissions from construction and demolition debris (C&D) landfills. Although several studies have reported the ambient concentrations of H2S near C&D landfills, few studies have quantified emission rates of H2S. One of the most widely used techniques for measuring surface gas emission rates from landfills is the flux chamber method. Flux measurements using the flux chamber were performed at five different C&D landfills from April to August, 2003. The flux rates of H2S measured in this research were between 0.192 and 1.76 mg/(m2-d).
Article
This study was conducted to determine the characteristics and biogas production potential of organic materials separated from municipal solid wastes using a rotary drum reactor (RDR) process. Four different types of wastes were first pretreated with a commercial RDR system at different retention times (1, 2 and 3 d) and the organic fractions were tested with batch anaerobic digesters with 2.6 g VS L(-1) initial loading. The four types of waste were: municipal solid waste (MSW), a mixture of MSW and paper waste, a mixture of MSW and biosolids, and a mixture of paper and biosolids. After 20 d of thermophilic digestion (50+/-1 degrees C), it was found that the biogas yields of the above materials were in the range of 457-557 mL g VS(-1) and the biogas contained 57.3-60.6% methane. The total solid and volatile solid reductions ranged from 50.2% to 65.0% and 51.8% to 66.8%, respectively. For each material, the change of retention time in the RDR from 1 to 3d did not show significant (alpha=0.05) influence on the biogas yields of the recovered organic materials. Further studies are needed to determine the minimum retention time requirements in the RDR system to achieve effective separation of organic from inorganic materials and produce suitable feedstock for anaerobic digesters.
Article
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008. This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. Includes bibliographical references (p. 107-114). Central to the study of stratospheric ozone recovery and climate change, is the ability to predict emissions of Montreal Protocol-restricted halocarbons (MPGs) over the coming decades. The prediction of emissions has become difficult as global production of MPGs has rapidly declined establishing "banks" (MPGs which have been produced but not yet released) as the main emission sources. Both the magnitude and release rate of global banks is quite uncertain. Very few field studies have been conducted to provide estimates of global bank emissions from individual sources within countries. This thesis provides the first known observation-based estimates of CFC-12, CFC-11,CFC-113, and CH3CCl3 emissions in the United States (US) and United Kingdom (UK) from municipal solid waste (MSW) landfills. With several hundred MSW landfills in both the US and UK, estimating emissions of MPGs from landfills required a targeted approach. Whole landfill mixing ratios and flow rates were sampled monthly at one landfill in southern Massachusetts to provide temporal coverage. Spatial coverage was achieved through one time sampling at seven landfills in Massachusetts and through data provided by nine UK landfills for CFC-12 and CFC-11. Only actively managed MSW landfills were sampled. US and UK MPG landfill emissions were estimated and compared to recent observation-based estimates of total US and UK MPG emissions to determine the importance of the landfill source. US MPG landfill emissions were estimated to be 0.008 - 0.08 Gg year-1. For all four MPGs, US landfill emissions were 0.6% of total US emissions. The UK landfill emission estimates were 6% and 0.8% of total UK CFC-12 and CFC-11 emissions, respectively. All estimates were accurate to within a factor of 2. This indicates that landfills are not currently a significant source of lingering MPG emissions in the US and UK. The implications are that the majority of MPG emissions in industrialized countries are likely coming from faster emitting sources. by Elke L. Hodson. Ph.D.
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This paper reviews alternatives for composting of combined municipal solid waste (MSW) and sewage sludge in a developing country, Vietnam. Near-term Vietnamese plans are for aerobic composting. Anaerobic composting of the same waste stream using a landfill reactor, i.e., ‘controlled landfilling’, is also evaluated. Anaerobic composting should provide a major energy benefit in terms of fuel gas recovery to maximum potential from the waste.
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Methane, an important atmospheric trace gas, controls numerous chemical processes and species in the troposphere and stratosphere. It is a strong greenhouse gas with a significantly adverse environmental impact. Mathane's concentration in the Earth's atmosphere has been increasing at a rate of about 1% per year during this century, and reached 1Â·72 ppm (by volume) in 1990. In this study, the individual sources of methane are identified and discussed. Available estimates of emission rates from these sources are presented. About 80% of methane in the atmosphere is produced biologically, whereas about 50% of the present sources are controlled by mankind. The accuracy of available estimates of emission rates, from individual sources, is poor; so more field measurements are still required for a more satisfactory evaluation of methane sources.
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Five types of food wastes were investigated as feedstock for a potential centralized anaerobic digester system in the area of Sacramento, California to produce biogas energy. The wastes were from a soup processing plant, a cafeteria, a commercial kitchen, a fish farm, and grease trap collection service. Digestibilities of the food wastes, individually and in mixtures, were conducted at mesophilic (35℃) and thermophilic (50℃) temperatures and at two food to microorganism ratios (F/M) of 0.5 and 1.0, for 28 days. A continuously fed mesophilic single-stage anaerobic digester was evaluated using a mixture of the five food wastes at organic loading rates of 0.5 to 1.0 g VS/L/d. In the batch digestion tests, fish and grease trap wastes required longer time to complete the digestion and had higher biogas yields than the other wastes. The continuously-fed digester required the addition of sodium hydroxide to maintain pH at proper levels in the digester. Alkalinity of about 2,500 mg CaCO 3 /L and pH above 7 was maintained by adding 0.2 g NaOH/g VS. The results of this study indicated that it was necessary to use the chemicals, such as NaOH, to control the pH of the single-stage anaerobic digester treating the food waste. For commercial applications, the cost of chemicals and proper management of additional salts in the digester effluent need to be carefully considered. Citation: Xiguang Chen, Rowena T. Romano, Ruihong Zhang. Anaerobic digestion of food wastes for biogas production. Int J Agric & Biol Eng, 2010; 3(4): 61－72.
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Chapter
Solid waste management (SWM) has always been an integral feature of every human society and has become a growing global concern as urban populations continue to grow as well as consumption patterns change. The health and environmental consequences of SWM are becoming increasingly urgent, particularly in developing countries. In this sense, sustainable and integrated solid waste management emerges as a solution to the growing global challenges of disposing of municipal solid waste (MSW). SWM is a cross-cutting issue that can be directly or indirectly linked to the 17 UN Sustainable Development Goals (SDGs) because it is an essential utility service. The three dimensions (or pillars) of sustainability are the environment, the economy, and society. Sustainable solid waste management (SWM) is a multifaceted issue with political, socioeconomic, institutional, and environmental components. It has become one of the most significant issues confronting urban spaces in developing countries as a result of exponential urban growth. Integrated solid waste management (ISWM) aims to optimize the management of solid waste from all waste-generating sectors, collection, transportation, and disposal while involving all stakeholders (waste generators, service providers, regulators, government, and community/neighborhoods).
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Chapter
As part of the transformation to achieve sustainable resource recovery and waste management, landfills play an important role. The landfill’s primary function is to accept solid wastes that cannot be “avoided, reduced, reused, recycled, or recovered.” Recognizing that residual waste composition has changed and will continue to evolve over time in response to technological advancements in recovery operations, it is critical that a precautionary approach be taken to properly mitigate the environmental risks of landfill facilities. Landfills must be built to have the least amount of negative environmental effects possible. The landfill’s design must take into account the surrounding area, the amount and nature of waste to be disposed of, the host community’s concerns, adjacent land use, and economic and social factors. Landfills should be planned and maintained in such a way that pollutants such as landfill gas, leachate, and stormwater are effectively managed. Monitoring is crucial for having a better understanding and trust in the site’s controls and risks, which advises management and treatment options. Rather than a monitoring program that validates impacts that have occurred, a monitoring program should be developed to cover all emissions and put a priority on monitoring to verify the efficacy of current controls, such as by monitoring leachate content, leachate levels, and surface water (groundwater monitoring).
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The global climate effects of time-dependent atmospheric trace gas and aerosol variations are simulated by NASA-Goddard's three-dimensional climate model II, which possesses 8 x 10-deg horizontal resolution, for the cases of a 100-year control run and three different atmospheric composition scenarios in which trace gas growth is respectively a continuation of current exponential trends, a reduced linear growth, and a rapid curtailment of emissions due to which net climate forcing no longer increases after the year 2000. The experiments begin in 1958, run to the present, and encompass measured or estimated changes in CO2, CH4, N2O, chlorofluorocarbons, and stratospheric aerosols. It is shown that the greenhouse warming effect may be clearly identifiable in the 1990s.
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It is pointed out that the release of chemicals into the atmosphere has grown greatly over the last 50 years. Contributed to the observed perturbations of trace chemicals in the atmosphere have an increased reliance on synthetic chemicals, deforestation, biomass burning, and fossil fuel combustion. As trace chemicals modify the radiation energy of the earth-atmosphere system, the considered developments can produce an alteration of the earth's climate. One of the major objectives of the present study is related to the characterization of the trace gases, taking into account the observed abundances, known sources, and sinks in the present-day atmosphere. Other objectives include an estimate of the future concentration of trace gases, an inference of the preindustrial concentrations of trace gases, and an estimate of the radiative effects of the trace gases and their potentials for climate changes.
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The report discusses technical, environmental, and other issues associated with using landfill gas as fuel, and presents case studies of projects in the U.S. illustrating some common energy uses. The full report begins by covering basic issues such as gas origin, composition, and means of collection; environmental and regulatory background is presented. Properties of landfill gas as a fuel are reviewed; equipment that can utilize landfill gas is discussed. The report then describes experience with six projects in the U.S. where landfill gas has been used for energy. It also references literature on other landfill gas energy projects of interest. Conclusions regarding uses of landfill gas for energy are presented.
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The paper discusses AEERL's research efforts on global landfill methane (CH4). CH4 is of particular concern because its radiative forcing potential is thought to be much greater than that of carbon dioxide. Although the major sources of CH4 are known qualitatively, considerable uncertainty exists about the quantitative emissions from each source. One goal of AEERL's global climate research program is to develop a more accurate inventory of CH4 emissions from landfills. For major sources of greenhouse gases, AEERL has a program to develop and demonstrate mitigation/control opportunities for sources that are amenable to cost-effective control. The paper describes how global landfill CH4 is being estimated and what work has been initiated relating to the mitigation of global landfill CH4.
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Knowledge of the quantities and composition of municipal solid waste (MSW) is a necessary tool for many aspects of solid-waste management. This report, which is an update of previous work in 1986, presents a summary of estimates of historical MSW quantities and composition from 1960 to 1986, with projections to the year 2000. The material-flows methodology developed by EPA in the early 1970s, with refinements that have been added in succeeding years, was used to make these estimates.
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The paper discusses a portion of EPA's global climate change program, a program plan for methane emissions from landfills and other waste disposal facilities. In response to concerns about global climate change, the U.S. EPA's Office of Research and Development (ORD) has initiated an emissions and mitigation program. ORD's Air and Energy Engineering Research Laboratory (AEERL) has begun research on greenhouse gas emission estimation, biomass and methane utilization, tropospheric ozone, and evaluation of potential mitigation opportunities for emissions contributing to global climate change. The emissions program has begun to identify and quantify emission sources of greenhouse gases for anthropogenic sources including landfills, coal mines, natural gas production/distribution, cook stoves, and biomass burning. Development of enhanced emission estimates will improve the understanding of atmospheric chemistry and feedback effects, target mitigation opportunities, and ensure cost-effective mitigation strategies. The focus of the paper is on AEERL's research efforts on global landfill methane.
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This paper reviews the climatic effects of trace gases such as carbon dioxide and methane. It discusses the expected changes from the increases in trace gases and the extent to which the expected changes can be found in the climate record and in the retreat of glaciers. The use of ice cores in correlating atmospheric composition and climate is discussed. The response of terrestrial ecosystems as a biotic feedback is discussed. Possible responses are discussed, including reduction in fossil-fuel use, controls on deforestation, and reforestation. International aspects, such as the implications for developing nations, are addressed.
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Methane is the most abundant organic chemical in Earth's atmosphere, and its concentration is increasing with time. Photochemical reactions oxidize methane in the atmosphere; through these reactions, methane exerts strong influence over the chemistry of the troposphere and the stratosphere and many species including ozone, hydroxyl radicals, and carbon monoxide. Also, through its infrared absorption spectrum, methane is an important greenhouse gas in the climate system. The key roles and reactions of methane are described and enumerated. Two kinds of methane production are examined in detail: microbial and thermogenic. Microbial methanogenesis is described, and key organisms and substrates are identified along with their properties and habitats. Microbial methane oxidation limits the release of methane from certain methanogenic areas. Both aerobic and anaerobic oxidation are described along with methods to measure rates of methane production and oxidation experimentally. Indicators of the origin of methane, including C and H isotopes, are reviewed. Several constraints on the budget of atmospheric methane, its sources, sinks and residence time are identified and evaluated. From these constraints and other data on sources and inks, a list of sources and sinks, identities, and sizes are constructed. 299 refs., 11 figs., 4 tabs.
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A carbon cycle model is presented in which direct ventilation of intermediate and deep ocean waters in high latitudes is taken into account. The 1 1/2 -dimensional ocean model is an extension of a box-diffusion model including a deep-sea outcrop at the surface. If both are calibrated in a consistent way, the outcrop-diffusion ocean takes up more excess CO2 than the box-diffusion ocean because the outcropping deep water is essentially virgin as to fossil CO2. Two calibration methods are compared, using the distribution either of natural or of bomb-produced 14C. The latter leads to a higher oceanic uptake of excess CO2 than the former and to a better agreement with the observed atmospheric increase. Long-term model responses are also discussed.
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Landfills are a significant source of methane, ranking third in anthropogenic sources after rice paddies and ruminants. Estimating the contribution of landfills to global methane flux is hampered by a lack of accurate refuse and landfill data, and therefore depends heavily on the assumptions used in the calculations. This paper describes research efforts to improve methodologies for estimating landfill emissions. Two key variables are discussed (1) the amount of refuse landfilled, and (2) the methanegenerating potential of that refuse. Estimates of annual U.S. municipal solid waste production are compared, and the limitations of each method are reviewed. The implications for global data development are discussed. The estimated amount of methane emitted due to anaerobic decomposition of refuse in landfills can be based on theoretical models, laboratory studies, or measurements. Data from methane recovery systems at selected U.S. landfills were used to evaluate the effect of climate, age of refuse, and physical characteristics of the site on methane recovery. Methodologies for using methane recovery data to estimate methane produced by refuse are described, and resulting methane potentials are compared to other values in the literature. This paper discusses the factors that influence these two key variables and the sensitivity of global methane emissions estimates to assumptions about these factors.
Article
Experiments were carried out in unstirred reactors for the digestion to fuel gas of shredded municipal solid waste and sewage sludge at high total solids concentration. Waste and sludge solids together comprised up to 48 percent by weight of the reactor contents. Finely divided calcium carbonate dispersed in the aqueous phase was employed as a pH buffer. Results of experiments showed that conversion to fuel gas of up to 0.128 m3/ kg (2.04 ft3 CH4 (STP)/lb) solid waste was obtained. In a separate experiment, alkaline pretreatment of the solid waste component preceding digestion further improved conversion to fuel gas. An engineering analysis was conducted for application of these results to a controlled landfill system. For an approximately 1.04 Gg/day (1150 U.S. tons/day) at 7 day/week municipal waste system, based on documented equipment costs and an accepted private utility financing method, the incremental capital cost to modify a landfill for fuel gas production was estimated to be $4.6 million, and incremental operating cost under$300,000 per year. Heating value of the fuel gas generated was estimated to be 1.33 × 106 GJ/year (1.26 trillion BTU/year) and the fuel gas cost was estimated to be near $0.70/GJ ($0.74/million BTU). It appears that the system evaluated has potential for making possible the economic recovery of fuel gas from solid waste (or other solid substrates) through substantial reduction in the capital and operating costs of a conventional anaerobic digestion system.
Article
Increased abundances were measured for several trace atmospheric gases in the decade 1970-1980. The equilibrium greenhouse warming for the measured increments of CH4, chlorofluorocarbons and N2O is between 50% and 100% of the equilibrium warming for the measured increase of atmospheric CO2 during the same 10 years. The combined warming of CO2 and trace gases should exceed natural global temperature variability in the 1980's and cause the global mean temperature to rise above the maximum of the late 1930's.
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The current concern about an anthropogenic impact on global climate has made it of interest to compare the potential effect of various human activities. A case in point is the comparison between the emission of greenhouse gases from the use of natural gas and that from other fossil fuels. This comparison requires an evaluation of the effect of methane emissions relative to that of carbon dioxide emissions. A rough analysis based on the use of currently accepted values shows that natural gas is preferable to other fossil fuels in consideration of the greenhouse effect as long as its leakage can be limited to 3 to 6 percent.
Article
Frequent atmospheric measurements of the anthropogenic compound methylchloroform that were made between 1978 and 1985 indicate that this species is continuing to increase significantly around the world. Reaction with the major atmospheric oxidant, the hydroxyl radical (OH), is the principal sink for this species. The observed mean trends for methylchloroform are 4.8, 5.4, 6.4, and 6.9 percent per year at Aldrigole (Ireland) and Cape Meares (Oregon), Ragged Point (Barbados), Point Matatula (American Samoa), and Cape Grim (Tasmania), respectively, from July 1978 to June 1985. These measured trends, combined with knowledge of industrial emissions, were used in an optimal estimation inversion scheme to deduce a globally averaged methylchloroform atmospheric lifetime of 6.3 (+ 1.2, -0.9) years (1sigma uncertainty) and a globally averaged tropospheric hydroxyl radical concentration of (7.7 +/- 1.4) x 10(5) radicals per cubic centimeter (1sigma uncertainty). These 7 years of gas chromatographic measurements, which comprise about 60,000 individual calibrated real-time air analyses, provide the most accurate estimates yet of the trends and lifetime of methylchloroform and of the global average for tropospheric hydroxyl radical levels. Accurate determination of hydroxyl radical levels is crucial to understanding global atmospheric chemical cycles and trends in the levels of trace gases such as methane.
Article
A comparison is made of the radiative (greenhouse) forcing of the climate system due to changes of atmospheric chlorofluorocarbons and other trace gases. It is found that CFCs, defined to include chlorofluorocarbons, chlorocarbons, and fluorocarbons, now provide about one-quater of current annual increases in anthropogenic greenhouse climate forcing. If the growth rates of CFC production in the early 1970s had continued to the present, current annual growth of climate forcing due to CFCs would exceed that due to CO2.
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The author reviews the performance, availability, and maintenance for ten photovoltaic plants since 1983. Problems are examined and achievable capacity factors are presented. The cost of photovoltaic electricity is developed as a function of investment cost, maintenance costs, and capacity factor, which in turn is shown to depend upon the site, the plant's availability, and the tracking employed
Landfill methane models
• Augenstein
Untersuchungen zur Entstehen, Ausbreitung, und Ableitung von Zersetzungsgasen in Abfallablagerungen
• Rettenberger
The use of mass balances for calculation of the methane potential of fresh and anaerobically decomposed refuse
• Barlaz
The cost of slowing climatic change
• Nordhaus
The federal tax credit for non-conventional fuels: Its status and role in the landfill gas industry
• Hatch