Landfilling Definition, Process and Methods Explained
Landfilling is the practice of disposing waste by depositing it in or on land, in successive layers which are compacted and covered. This article discusses landfilling definition, process and methods, as follows;
-Landfilling Definition: 6 Ways to Define Landfilling
-Steps in the Landfilling Process
Landfilling Definition: 6 Ways to Define Landfilling
Landfilling is a waste management system or practice whereby large amounts of waste material are buried successively beneath and between layers of earth material [6].
As a system of waste management, landfilling is sometimes viewed as an unsustainable alternative to other systems and practices like recycling [1].
Aside waste management, landfilling can be practiced as a measure for soil restoration, in areas that have been affected by severe erosion or natural hazards like landslides.
The landfilling definition below highlights some potential environmental impacts of landfilling;
Landfilling is the act of depositing large volumes of earth material or waste into a trench, hole, or depressed area of land in a bid to dispose it and/or recover the land resource; with side effects like leachate production, soil and groundwater pollution, open biodegradation, and greenhouse gas emission [5].
It must be mentioned that the risk of environmental degradation as a result of landfilling can be reduced drastically if the practice is carried out efficiently, according to existing standards and guidelines.
While it is not seen as a waste-to-energy technique; landfilling leads to the production of renewable fuel. This fact is further clarified in the landfilling definition below;
Landfilling is a system of waste disposal that leads to the generation of biomethane; also called biogas or landfill gas, by the decomposition of organic materials in landfill sites, under partial anaerobic conditions [4].
The above definition implies that biomass is one of the types of waste that are disposed through landfilling. In the landfilling definition below, other types of waste disposed in landfills are mentioned;
Landfilling is a waste management and land recovery method whereby various materials like municipal solid waste, agricultural, commercial and industrial waste; are introduced into land and buried underneath layers of earth, in order to dispose of them.
In line with the definition above, landfilling can in fact be defined based on the types of waste which are introduced into a landfill. Landfilling of solid waste, or municipal solid waste landfilling (MSWLF), is simply the introduction and burial of municipal solid waste materials in holes, trenches or other depressed land areas.
Below is another landfilling definition that mentions some methods of landfilling;
Landfilling is the deliberate introduction of waste materials into depressed, eroded or excavated land, using the trench, area or ramp method; as a means of disposing these materials and recovering lost land resources [2].
It is important to note that energy recovered from landfill gas can be described as bioenergy, which is a type of renewable energy. This is because the gas is a biofuel, and produced by the decomposition of renewable organic matter.
However, landfilling is not widely considered to be a sustainable method of waste disposal, energy recovery, or land resources recovery.
Steps in the Landfilling Process
The landfilling process is made up of three steps which are; introduction, compaction and coverage.
These three landfilling process steps are each briefly discussed below;
1). Introduction (as one of the Landfilling Process Steps)
The first step in the landfilling process is introduction, or dumping, of materials in the landfill. It is also one of the most important stages in the landfilling process.
At the stage of introduction, care can be taken to select what types of waste are suitable for disposal in a landfill. Generally, this is determined by the composition and nature of the materials, as well as the soil type, topography and drainage characteristics of the landfill site.
To optimize the safety of landfilling and mitigate environmental impacts, some standard practices and guidelines are recommended.
The depth of the landfill itself should be at least 1.8 meters.
At the bottom of the landfill, an impervious or semi-permeable material should be laid to minimize contact with the soil and possible pollution of both soil and groundwater. Materials that can be used include geosynthetic clays, and the minimum recommended thickness is 60 millimeters.
However, this thickness may much be less than 60mm in some cases, depending on the material used, among other factors.
As part of best practices in a well-engineered landfilling project, the landfill should be equipped with pipes and collection equipment for isolation, collection and treatment of leachate, landfill gas, and other materials that can be harmful to the ecosystem if released [3].
Lastly, the waste materials introduced into the landfill should be spread out in thin layers for each successive introduction; with a maximum recommended thickness of one meter.
This will allow for easy and effective compaction, which is the next step in the landfilling process;
2). Compaction
The waste which has been introduced into the landfill is subsequently compacted using earthmoving equipment.
The reasons for this include to increase the density of the waste layers to make them serve effectively for land recovery; and to reduce the risk of entry of vermin that can cause environmental degradation, and disease outbreak.
Compaction also helps slow the rate of biodegradation, and improves the function of the soil as a carbon sink.
3). Coverage (as one of the Landfilling Process Steps)
After compaction, the waste in landfills should be covered with a thin layer of soil.
This practice helps reduce offensive odors, while protecting the waste from birds, rodents, and insects; and reducing rainwater infiltration which can accelerate leachate formation.
Ideally, the soil layer must be at least six inches thick after it has been compacted.
Landfilling Methods
Landfilling Methods are area, trench, and ramp methods.
The two main landfilling methods are area and trench method, while ramp method is a hybrid approach that combines characteristics of each of the two main methods.
They are each discussed below;
1). Trench Landfilling (as one of the Landfilling Methods)
Trench method of landfilling has to do with the excavation of shallow trenches in land, in which waste material is deposited.
The method is ideal for cases where the landfill site has flat topography, good drainage, and low water table.
Precautions to be taken when practicing the trench method of landfilling include the use of liners at the bottom of the trenches, excavation to a depth that does not get close to the water table.
In trench landfilling, the volume of waste that can be disposed at any given time is relatively small, but may be upscaled by increasing the size of the trenches.
2). Area Landfilling
Area method of landfilling involves the deposition of waste in thin layers on the earth’s surface, where it is compacted and covered with soil for each successive layer of deposition.
The area landfilling method is practiced in sites where the geographic, hydrological and geological conditions are not suitable for any form of excavation and dumping.
Such sites include those with high water table (groundwater level), unfavorable or inefficient drainage, sensitive soil, or where extensive degradation has occurred.
Former mining sites, and sites that have been polluted in severe cases of oil spill are examples of suitable locations for area landfilling.
Area landfilling can also serve as part of an environmental remediation strategy in such sites; namely bioremediation. The biochemical process occurring in the soil as a result of the presence of landfill waste, can help reduce the concentration of pollutants. However, this approach for remediation is not recommendable.
3). Ramp Landfilling (as one of the Landfilling Methods)
The landfilling ramp method is a less-common method which combines the characteristics of both area and trench methods.
It is based on shallow excavation, successive waste dumping, and coverage; and is most suited to sites with undulating topography. In such sites, the ramps produced in the process of landfilling, can help to fill-out uneven areas and recover the land.
Sites with flat topography are also suitable for ramp landfilling.
Conclusion
Landfilling is a waste management and land recovery practice involving the successive dumping, compaction and coverage of waste materials in trenches, depressions or land surfaces.
Steps in the landfilling process are;
1. Introduction
2. Compaction
3. Coverage
Methods of landfilling are;
1. Trench Landfilling
2. Area Landfilling
3. Ramp Landfilling
References
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2). Ersoy, H.; Bulut, F.; Berkun, M. (2013). “Landfill site requirements on the rock environment: A case study.” Engineering Geology 154:20–35. Available at: https://doi.org/10.1016/j.enggeo.2012.12.005. (Accessed 4 November 2022).
3). Ghazali, M. A.; Sapari, N.; Olisa, E.; Jusoh, H. (2014). “Landfill Gas Detection in Leachate Pipe: A Consideration for Design Improvement of Leachate Piping and Gas Venting Systems.” Applied Mechanics and Materials 699:607-612. Available at: https://doi.org/10.4028/www.scientific.net/AMM.699.607. (Accessed 4 November 2022).
4). Leme, M. A.; Torres-Mayanga, P. C.; Perez, D. L.; Forster-Carneiro, T.; Miguel, M. G. (2022). “Biogas production from the landfilled easily degradable fraction of municipal solid waste: mining strategy for energy recovery.” Biomass Conversion and Biorefinery. Available at: https://doi.org/10.1007/s13399-022-03264-9. (Accessed 4 November 2022).
5). Mabunga, Z.; Magwili, G. (2019). “Greenhouse Gas Emissions and Groundwater Leachate Leakage Monitoring of Sanitary Landfill.” IEEE 11th International Conference on Humanoid, Nanotechnology, Information Technology, Communication and Control, Environment, and Management ( HNICEM ). Available at: https://doi.org/10.1109/HNICEM48295.2019.9072872. (Accessed 4 November 2022).
6). Siddiqua, A.; Hahladakis, J. N.; Al-Attiya, W. A. (2022). “An overview of the environmental pollution and health effects associated with waste landfilling and open dumping.” Environmental Science and Pollution Research 29(Suppl 1):1-23. Available at: https://doi.org/10.1007/s11356-022-21578-z. (Accessed 4 November 2022).
