Wikipedia

Landfill

For the practice of filling a body of water to create new land, seeLand reclamation.For other uses, seeLandfill (disambiguation).

Alandfill[a]is a site for the disposal ofwastematerials. It is the oldest and most common form ofwaste disposal,although the systematic burial of waste with daily, intermediate and final covers only began in the 1940s. In the past, waste was simply left in piles or thrown into pits (known inarcheologyasmiddens).

Some landfill sites are used for waste management purposes, such as temporary storage, consolidation and transfer, or for various stages of processing waste material, such as sorting, treatment, or recycling. Unless they are stabilized, landfills may undergo severe shaking orsoil liquefactionof the ground during anearthquake.Once full, the area over a landfill site may bereclaimedfor other uses.

Operations

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One of several landfills used byDryden, Ontario,Canada
Garbage dumped in the middle of a road inKarachi,Pakistan

Operators of well-run landfills for non-hazardous waste meet predefined specifications by applying techniques to:[1]

  1. confine waste to as small an area as possible
  2. compact waste to reduce volume[2]

They can also cover waste (usually daily) with layers of soil or other types of material such as woodchips and fine particles.

During landfill operations, ascaleorweighbridgemay weigh waste collection vehicles on arrival and personnel may inspect loads for wastes that do not accord with the landfill's waste-acceptance criteria.[2]Afterward, the waste collection vehicles use the existing road network on their way to the tipping face or working front, where they unload their contents. After loads are deposited,compactorsor bulldozers can spread andcompact the wasteon the working face. Before leaving the landfill boundaries, the waste collection vehicles may pass through a wheel-cleaning facility. If necessary, they return to the weighbridge for re-weighing without their load. The weighing process can assemble statistics on the daily incoming waste tonnage, which databases can retain for record keeping. In addition to trucks, some landfills may have equipment to handle railroad containers. The use of "rail-haul" permits landfills to be located at more remote sites, without the problems associated with many truck trips.

Typically, in the working face, the compacted waste is covered with soil or alternative materials daily. Alternative waste-cover materials include chipped wood or other "green waste",[3]several sprayed-on foam products, chemically "fixed" bio-solids, and temporary blankets. Blankets can be lifted into place at night and then removed the following day prior to waste placement. The space that is occupied daily by the compacted waste and the cover material is called a daily cell. Waste compaction is critical to extending the life of the landfill. Factors such as waste compressibility, waste-layer thickness and the number of passes of the compactor over the waste affect the waste densities.

Sanitary landfill life cycle

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Sanitary landfill diagram

The termlandfillis usually shorthand for a municipal landfill or sanitary landfill. These facilities were first introduced early in the 20th century, but gained wide use in the 1960s and 1970s, in an effort to eliminate open dumps and other "unsanitary" waste disposal practices. The sanitary landfill is an engineered facility that separates and confines waste. Sanitary landfills are intended as biological reactors (bioreactors) in which microbes will break down complex organic waste into simpler, less toxic compounds over time. These reactors must be designed and operated according to regulatory standards and guidelines (Seeenvironmental engineering).

Usually, aerobic decomposition is the first stage by which wastes are broken down in a landfill. These are followed by four stages of anaerobic degradation. Usually, solid organic material in solid phase decays rapidly as larger organic molecules degrade into smaller molecules. These smaller organic molecules begin to dissolve and move to the liquid phase, followed by hydrolysis of these organic molecules, and the hydrolyzed compounds then undergo transformation and volatilization as carbon dioxide (CO2) and methane (CH4), with rest of the waste remaining in solid and liquid phases.

During the early phases, little material volume reaches theleachate,as the biodegradable organic matter of the waste undergoes a rapid decrease in volume. Meanwhile, the leachate'schemical oxygen demandincreases with increasing concentrations of the more recalcitrant compounds compared to the more reactive compounds in the leachate. Successful conversion and stabilization of the waste depend on how well microbial populations function insyntrophy,i.e. an interaction of different populations to provide each other's nutritional needs.:[4]

The life cycle of a municipal landfill undergoes five distinct phases:[5][4]

Initial adjustment (Phase I)

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As the waste is placed in the landfill, the void spaces contain high volumes of molecular oxygen (O2). With added and compacted wastes, the O2content of the landfill bioreactor strata gradually decreases. Microbial populations grow, density increases. Aerobic biodegradation dominates, i.e. the primary electron acceptor is O2.

Transition (Phase II)

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The O2is rapidly degraded by the existing microbial populations. The decreasing O2leads to less aerobic and more anaerobic conditions in the layers. The primary electron acceptors during transition are nitrates and sulphates since O2is rapidly displaced by CO2in the effluent gas.

Acid formation (Phase III)

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Hydrolysis of the biodegradable fraction of the solid waste begins in the acid formation phase, which leads to rapid accumulation ofvolatile fatty acids(VFAs) in the leachate. The increased organic acid content decreases the leachatepHfrom approximately 7.5 to 5.6. During this phase, the decomposition intermediate compounds like the VFAs contribute muchchemical oxygen demand(COD). Long-chain volatile organic acids (VOAs) are converted to acetic acid (C2H4O2), CO2,and hydrogen gas (H2). High concentrations of VFAs increase both thebiochemical oxygen demand(BOD) and VOA concentrations, which initiates H2production by fermentative bacteria, which stimulates the growth of H2-oxidizing bacteria. The H2generation phase is relatively short because it is complete by the end of the acid formation phase. The increase in the biomass ofacidogenicbacteria increases the amount of degradation of the waste material and consuming nutrients. Metals, which are generally more water-soluble at lower pH, may become more mobile during this phase, leading to increasing metal concentrations in the leachate.

Methane fermentation (Phase IV)

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The acid formation phase intermediary products (e.g., acetic, propionic, and butyric acids) are converted to CH4and CO2by methanogenic microorganisms. As VFAs are metabolized by the methanogens, the landfill water pH returns to neutrality. The leachate's organic strength, expressed as oxygen demand, decreases at a rapid rate with increases in CH4and CO2gas production. This is the longest decomposition phase.

Final maturation and stabilization (Phase V)

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The rate of microbiological activity slows during the last phase of waste decomposition as the supply of nutrients limits the chemical reactions, e.g. asbioavailablephosphorus becomes increasingly scarce. CH4production almost completely disappears, with O2and oxidized species gradually reappearing in the gas wells as O2permeates downwardly from the troposphere. This transforms theoxidation–reductionpotential (ORP) in the leachate toward oxidative processes. The residual organic materials may incrementally be converted to the gas phase, and as organic matter is composted; i.e. the organic matter is converted tohumic-like compounds.[6]

Social and environmental impact

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Landfill operation in Hawaii. The area being filled is a single, well-defined "cell" and a protectivelandfill lineris in place (exposed on the left) to prevent contamination byleachatesmigrating downward through the underlying geological formation.

Landfills have the potential to cause a number of issues.Infrastructuredisruption, such as damage to access roads by heavy vehicles, may occur. Pollution of local roads and watercourses from wheels on vehicles when they leave the landfill can be significant and can be mitigated bywheel washing systems.Pollutionof the localenvironment,such as contamination ofgroundwateroraquifersorsoil contaminationmay occur, as well.

Leachate

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Main article:Leachate

When precipitation falls on open landfills, water percolates through the garbage and becomes contaminated with suspended and dissolved material, forming leachate. If this is not contained it can contaminate groundwater. All modern landfill sites use a combination of impermeable liners several metres thick, geologically stable sites and collection systems to contain and capture this leachate. It can then be treated and evaporated. Once a landfill site is full, it is sealed off to prevent precipitation ingress and new leachate formation. However, liners must have a lifespan, be it several hundred years or more. Eventually, any landfill liner could leak,[7]so the ground around landfills must be tested for leachate to prevent pollutants from contaminating groundwater.

Decomposition gases

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Main article:Landfill gas

Rotting food and other decaying organic waste createdecomposition gases,especially CO2and CH4from aerobic and anaerobic decomposition, respectively. Both processes occur simultaneously in different parts of a landfill. In addition to available O2,the fraction of gas constituents will vary, depending on the age of landfill, type of waste, moisture content and other factors. For example, the maximum amount of landfill gas produced can be illustrated a simplified net reaction of diethyl oxalate that accounts for these simultaneous reactions:[8]

4 C6H10O4+ 6 H2O → 13 CH4+ 11 CO2

On average, about half of the volumetric concentration of landfill gas is CH4and slightly less than half is CO2.The gas also contains about 5% molecular nitrogen (N2), less than 1%hydrogen sulfide(H2S), and a low concentration ofnon-methane organic compounds (NMOC),about 2700ppmv.[8]

Waste disposal in Athens, Greece

Landfill gases can seep out of the landfill and into the surrounding air and soil.Methaneis agreenhouse gas,and is flammable and potentially explosive at certain concentrations, which makes it perfect for burning to generate electricity cleanly. Since decomposing plant matter and food waste only release carbon that has been captured from the atmosphere through photosynthesis, no new carbon enters thecarbon cycleand the atmospheric concentration of CO2is not affected. Carbon dioxide traps heat in the atmosphere, contributing toclimate change.[9]In properly managed landfills, gas is collected andflaredor recovered forlandfill gas utilization.

Vectors

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Poorly run landfills may become nuisances because ofvectorssuch as rats and flies which can spreadinfectious diseases.The occurrence of such vectors can be mitigated through the use ofdaily cover.

Other nuisances

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A group of wild elephants interacting with a trash dump in Sri Lanka

Other potential issues includewildlifedisruption due to occupation of habitat[10]and animal health disruption caused by consuming waste from landfills,[11]dust, odor,noise pollution,and reduced local property values.

Landfill gas

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Main article:Landfill gas
A gas flare produced by a landfill inLake County, Ohio

Gases are produced in landfills due to theanaerobic digestionby microbes. In a properly managed landfill, this gas is collected and used. Its uses range from simpleflaringto thelandfill gas utilizationandgeneration of electricity.Landfill gas monitoring alerts workers to the presence of a build-up of gases to a harmful level. In some countries, landfill gas recovery is extensive; in the United States, for example, more than 850 landfills have active landfill gas recovery systems.[12]

Solar landfill

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Solar arrayson a full landfill inRehoboth, MA

ASolar landfillis a repurposed used landfill that is converted to asolar arraysolar farm.[13]

Regional practice

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A landfill in Perth, Western Australia
South East New Territories Landfill,Hong Kong

Canada

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Landfills in Canada are regulated by provincial environmental agencies and environmental protection legislation.[14] Older facilities tend to fall under current standards and are monitored forleaching.[15]Some former locations have been converted to parkland.

European Union

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The Rusko landfill inOulu, Finland

In the European Union, individual states are obliged to enact legislation to comply with the requirements and obligations of the EuropeanLandfill Directive.

The majority of EU member states have laws banning or severely restricting the disposal of household trash via landfills.[16]

India

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Landfilling is currently the major method of municipal waste disposal in India. India also has Asia's largest dumping ground in Deonar, Mumbai.[17]However, issues frequently arise due to the alarming growth rate of landfills and poor management by authorities.[18]On and under surface fires have been commonly seen in the Indian landfills over the last few years.[17]

United Kingdom

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Main article:Landfills in the United Kingdom

Landfilling practices in the UK have had to change in recent years to meet the challenges of the EuropeanLandfill Directive.The UK now imposes landfill tax uponbiodegradable wastewhich is put into landfills. In addition to this theLandfill Allowance Trading Schemehas been established for local authorities to trade landfill quotas in England. A different system operates inWaleswhere authorities cannot 'trade' amongst themselves, but have allowances known as the Landfill Allowance Scheme.

United States

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Main article:Landfills in the United States

U.S. landfills are regulated by each state's environmental agency, which establishes minimum guidelines; however, none of these standards may fall below those set by theUnited States Environmental Protection Agency(EPA).[19]

Permitting a landfill generally takes between five and seven years, costs millions of dollars and requires rigorous siting, engineering and environmental studies and demonstrations to ensure local environmental and safety concerns are satisfied.[20]

Types

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Microbial topics

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The status of a landfill's microbial community may determine its digestive efficiency.[23]

Bacteria that digest plastic have been found in landfills.[24]

Reclaiming materials

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Main article:Landfill mining

One can treat landfills as a viable and abundant source of materials andenergy.In the developing world,waste pickersoften scavenge for still-usable materials. Incommercialcontexts, companies have also discovered landfill sites, and many[quantify]have begun harvesting materials and energy.[25]Well-known examples include gas-recovery facilities.[26] Other commercial facilities include wasteincineratorswhich have built-in material recovery. This material recovery is possible through the use offilters(electro filter,active-carbonand potassium filter, quench, HCl-washer, SO2-washer,bottom ash-grating, etc.).

Alternatives

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See also:List of solid waste treatment technologies

In addition towaste reductionandrecyclingstrategies, there are various alternatives to landfills, includingwaste-to-energyincineration,anaerobic digestion,composting,mechanical biological treatment,pyrolysisandplasma arc gasification.Depending on local economics and incentives, these can be made more financially attractive than landfills.

Restrictions

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Countries includingGermany,Austria,Sweden,[27]Denmark,Belgium,theNetherlands,andSwitzerland,have banned the disposal of untreated waste in landfills.[citation needed]In these countries, only certain hazardous wastes,fly ashesfromincinerationor the stabilized output ofmechanical biological treatmentplants may still be deposited.[citation needed]

See also

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Notes

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  1. ^Also known as atip,dump,rubbish dump,garbage dump,trash dump,ordumping ground.

References

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  1. ^"Waste Management. Background information. General objectives of waste policy"(PDF).sustainabledevelopment.un.org.RetrievedMay 10,2024.
  2. ^ab"How a Landfill Operates".co.cumberland.nc.us.RetrievedFebruary 22,2020.
  3. ^"Alternative Daily Cover (ADC)".Archived fromthe originalon June 5, 2012.RetrievedSeptember 14,2012.
  4. ^abLetcher, T.M.; Vallero, D.A., eds. (2019).Municipal Landfill, D. Vallero and G. Blight, pp. 235–249 in Waste: A Handbook for Management.Amsterdam, Netherlands and Boston MA, Print Book: Elsevier Academic Press.ISBN9780128150603.804 pages.
  5. ^U.S. Environmental Protection Agency (2007) Landfill bioreactor performance: second interim report: outer loop recycling & disposal facility - Louisville, Kentucky, EPA/600/R-07/060
  6. ^Weitz, Keith; Barlaz, Morton; Ranjithan, Ranji; Brill, Downey; Thorneloe, Susan; Ham, Robert (July 1999). "Life Cycle Management of Municipal Solid Waste".The International Journal of Life Cycle Assessment.4(4): 195–201.Bibcode:1999IJLCA...4..195W.doi:10.1007/BF02979496.ISSN0948-3349.S2CID108698198.
  7. ^US EPA, "Solid Waste Disposal Facility Criteria; Proposed Rule", Federal Register 53(168):33314–33422, 40 CFR Parts 257 and 258, US EPA, Washington, D.C., August 30 (1988a).
  8. ^abThemelis, Nickolas J., and Priscilla A. Ulloa. "Methane generation in landfills." Renewable Energy 32.7 (2007), 1243–1257
  9. ^"CO2 101: Why is carbon dioxide bad?".Mother Nature Network.RetrievedNovember 30,2016.
  10. ^"How does landfill and litter affect our wildlife?".MY ZERO WASTE.January 30, 2009.RetrievedFebruary 22,2020.
  11. ^"Landfills are Ruining Lives".cdenviro.RetrievedFebruary 22,2020.
  12. ^Powell, Jon T.; Townsend, Timothy G.; Zimmerman, Julie B. (September 21, 2015). "Estimates of solid waste disposal rates and reduction targets for landfill gas emissions".Nature Climate Change.6(2): 162–165.doi:10.1038/nclimate2804.
  13. ^"U.S. Landfills Are Getting a Second Life as Solar Farms".TIME.June 2, 2022.
  14. ^"Ministry of the Environment, Conservation and Parks | ontario.ca".ontario.ca.
  15. ^"Aging Landfills: Ontario's Forgotten Polluterswork=Eco Issues".September 28, 2010. Archived fromthe originalon September 28, 2010.
  16. ^"CEWEP - The Confederation of European Waste-to-Energy Plants".
  17. ^ab"Fighting Mountains Of Garbage: Here Is How Indian Cities Dealt With Landfill Crisis In 2018 | Swachh Year Ender".NDTV.December 31, 2018.RetrievedFebruary 21,2020.
  18. ^Cassella, Carly (June 5, 2019)."India's 'Mount Everest' of Trash Is Growing So Fast, It Needs Aircraft Warning Lights".ScienceAlert.RetrievedFebruary 21,2020.
  19. ^Horinko, Marianne, Cathryn Courtin."Waste Management: A Half Century of Progress."EPA Alumni Association. March 2016.
  20. ^"Modern landfills".Archived fromthe originalon February 22, 2015.RetrievedFebruary 21,2015.
  21. ^EPA, OSWER, ORCR, US (March 24, 2016)."Basic Information about Landfills".epa.gov.RetrievedMarch 14,2017.{{cite web}}:CS1 maint: multiple names: authors list (link)
  22. ^"Disposal and Storage of Polychlorinated Biphenyl (PCB) Waste".United States Environmental Protection Agency.August 19, 2015.RetrievedMay 10,2017.
  23. ^Gomez, A.M.; Yannarell, A.C.; Sims, G.K.; Cadavid-Resterpoa, G.; Herrera, C.X.M. (2011). "Characterization of bacterial diversity at different depths in the Moravia Hill Landfill site at Medellín, Colombia".Soil Biology and Biochemistry.43(6): 1275–1284.Bibcode:2011SBiBi..43.1275G.doi:10.1016/j.soilbio.2011.02.018.
  24. ^Gwyneth Dickey Zaikab (March 2011)."Marine microbes digest plastic".Nature.doi:10.1038/news.2011.191.
  25. ^"Sinologie Spectrum".chinalize.nl.Archived fromthe originalon December 8, 2009.
  26. ^"Commercial exploitation of gas from landfills".Archived fromthe originalon October 24, 2011.RetrievedNovember 28,2009.
  27. ^"Regeringskansliets rättsdatabaser".rkrattsbaser.gov.se(in Swedish).RetrievedMay 9,2019.

Further reading

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