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. ...
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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). ...
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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;. ...
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Chapter
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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.
Article
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.
Article
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.
Article
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.
Article
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