What Happens When Organic Matter Is Deposited In Landfills?

Decomposition of organic matter in landfills is a complex process that can have both negative and positive impacts on the environment. If you’re short on time, here’s a quick answer to your question: When organic waste like food scraps, yard trimmings, paper, and wood are buried in landfills, they undergo anaerobic decomposition and produce methane gas. Methane contributes to climate change and can be dangerous if it migrates into nearby homes and buildings.

In this approximately 3000 word article, we will take an in-depth look at the science behind landfill decomposition. We will examine the conditions in modern landfills, the microorganisms involved, the decay process, and the end products formed. We will also discuss the pros and cons of diverting organics to landfills versus other waste management options like composting and anaerobic digestion. Read on to learn all about what really happens when organic matter ends up in the landfill.

How Modern Landfills Are Designed

Modern landfills are carefully designed to minimize the environmental impact of organic matter deposition. Here are some key elements of their design:

Liner and leachate collection systems

One important component of modern landfills is the liner system. Typically made of high-density polyethylene (HDPE) or clay, the liner acts as a barrier to prevent the leaching of harmful substances into the surrounding soil and groundwater. This helps protect the environment from potential contamination.

In addition to the liner, landfills also incorporate leachate collection systems. Leachate is the liquid that is produced when water comes into contact with decomposing organic matter. The collection system ensures that leachate is properly managed and treated to prevent any potential pollution.

Cover materials

Cover materials play a crucial role in minimizing odors and controlling the release of gases from the landfill. Typically, a layer of soil or special synthetic materials is used to cover the waste at the end of each day. This helps to contain odors and reduce the potential for the release of methane and other greenhouse gases into the atmosphere.

It’s important to note that the selection of cover materials is carefully considered to ensure they are effective in minimizing environmental impact while also being cost-effective for landfill operators.

Methane collection systems

Methane is a potent greenhouse gas that is produced during the decomposition of organic matter in landfills. To mitigate its impact on climate change, modern landfills incorporate methane collection systems. These systems capture the methane gas and either burn it off or convert it into usable energy.

The captured methane can be used to generate electricity, heat buildings, or even power vehicles. This not only helps reduce greenhouse gas emissions but also provides a sustainable source of energy.

By incorporating these design features, modern landfills are able to effectively manage the deposition of organic matter while minimizing their impact on the environment. It is important to note that the design and operation of landfills are regulated by environmental agencies to ensure compliance with strict standards and guidelines.

The Decomposition Process

When organic matter is deposited in landfills, it goes through a natural decomposition process. This process can be divided into three distinct phases: aerobic decomposition, anaerobic fermentation, and methanogenesis. Let’s take a closer look at each phase.

Phase 1: Aerobic Decomposition

In the initial phase, known as aerobic decomposition, organic matter is exposed to oxygen. This phase occurs when the waste is freshly deposited in the landfill. Bacteria and other microorganisms start breaking down the organic materials, such as food scraps, yard waste, and paper. During this phase, the decomposition process is relatively fast, and the waste volume decreases significantly.

Aerobic decomposition is an essential step in landfill management as it helps to minimize the production of methane gas, which is a potent greenhouse gas. Landfill operators often take measures to increase oxygen levels in the landfill, such as using aeration systems or regularly turning the waste to promote aerobic conditions.

Phase 2: Anaerobic Fermentation

As the decomposition process continues, the landfill becomes more compacted, and oxygen becomes limited. This leads to the next phase, known as anaerobic fermentation. In this phase, bacteria break down the remaining organic matter in the absence of oxygen. This process produces various by-products, including organic acids, alcohols, and gases such as carbon dioxide and methane.

Anaerobic fermentation is responsible for the majority of the methane gas emissions from landfills. Methane is a potent greenhouse gas that contributes to climate change. To mitigate these emissions, landfill operators employ various techniques, such as capturing and flaring the methane gas or using it as a renewable energy source.

Phase 3: Methanogenesis

The final phase of the decomposition process is called methanogenesis. During this phase, methane-producing bacteria called methanogens thrive in the anaerobic conditions of the landfill. These bacteria consume the organic acids and other by-products produced during anaerobic fermentation and convert them into methane gas. Methanogenesis can continue for several years, even after the landfill is closed.

It is worth noting that the decomposition process in landfills is influenced by various factors, including temperature, moisture levels, and the types of organic waste deposited. These factors can affect the speed and efficiency of decomposition, as well as the amount of methane gas produced.

For more information on landfill decomposition and waste management practices, you can visit websites such as www.epa.gov/landfills or www.wastecare.com.

Microorganisms Involved

When organic matter is deposited in landfills, various microorganisms play a crucial role in the decomposition process. These microorganisms, including bacteria, fungi, and archaea, break down the organic waste and convert it into simpler compounds.


Bacteria are the most abundant and diverse group of microorganisms found in landfills. They are responsible for breaking down organic matter by secreting enzymes that break down complex molecules into smaller ones. Some bacteria are specialized in degrading specific types of organic waste, while others have a broader range of capabilities. For example, cellulose-degrading bacteria break down plant fibers, while nitrogen-fixing bacteria convert atmospheric nitrogen into a usable form for plants.


Fungi, such as molds and yeasts, also play a significant role in the decomposition of organic matter in landfills. They are particularly efficient in breaking down complex compounds, such as lignin and chitin, which are resistant to degradation by bacteria. Fungi secrete enzymes that help break down these compounds, allowing other microorganisms to further decompose the organic waste. Additionally, fungi are involved in the formation of humus, a dark organic material that improves soil fertility.


Archaea are a group of microorganisms that were once classified as bacteria but are now recognized as a distinct group. They are found in various environments, including landfills, where they contribute to the decomposition of organic matter. Some archaea are known for their ability to thrive in extreme conditions, such as high temperatures or acidity. In landfills, archaea are involved in the breakdown of complex organic compounds, such as methane production from organic waste.

It is important to note that the composition and activity of microorganisms in landfills can vary depending on factors such as temperature, moisture, and the type of organic waste deposited. Therefore, the efficiency of decomposition and the byproducts produced can differ between landfills.

If you’d like to learn more about the microorganisms involved in the decomposition of organic matter in landfills, you can visit reputable sources such as the Environmental Protection Agency (EPA) or National Center for Biotechnology Information (NCBI).

End Products of Anaerobic Decomposition

When organic matter is deposited in landfills, it undergoes a process called anaerobic decomposition. This process occurs in the absence of oxygen and leads to the production of various end products. Let’s take a closer look at some of these end products:


One of the main end products of anaerobic decomposition is methane gas. Methane is a potent greenhouse gas that contributes to climate change. It is formed when organic matter, such as food waste and yard trimmings, breaks down in the absence of oxygen. Landfills are one of the largest sources of methane emissions globally. According to the Environmental Protection Agency (EPA), landfills accounted for about 15% of total methane emissions in the United States in 2020.

Carbon dioxide

Another significant end product of anaerobic decomposition is carbon dioxide. As organic matter decomposes, it releases carbon dioxide into the atmosphere. While carbon dioxide is also a greenhouse gas, it is less potent than methane. However, it still contributes to global warming and climate change. Landfills are a significant source of carbon dioxide emissions, and reducing these emissions is crucial for mitigating the impacts of climate change.


During anaerobic decomposition, organic matter also produces ammonia. Ammonia is a compound that contains nitrogen and is often associated with a strong, pungent odor. It is primarily released from decomposing animal waste and can contribute to air pollution and water contamination if not properly managed. Landfills that accept organic waste, such as livestock manure or food scraps, can release significant amounts of ammonia into the environment.

Hydrogen sulfide

Hydrogen sulfide is another byproduct of anaerobic decomposition. It is a colorless gas with a distinct rotten egg smell. Hydrogen sulfide is highly toxic and can be harmful to both human health and the environment. In high concentrations, it can cause respiratory issues, eye irritation, and even death. Landfills that receive organic waste, particularly sulfur-containing materials, can release hydrogen sulfide gas into the air, posing potential health risks to nearby communities.


In addition to gases, anaerobic decomposition also produces leachate. Leachate is a liquid that forms as water filters through the waste in a landfill, picking up various contaminants along the way. It can contain a range of pollutants, including heavy metals, organic compounds, and pathogens, making it a significant environmental concern. Proper management and treatment of leachate are crucial to prevent contamination of groundwater and surface water sources.

Environmental Impacts of Landfill Organic Waste

Climate change contributions

When organic matter is deposited in landfills, it undergoes anaerobic decomposition, which produces methane gas. Methane is a potent greenhouse gas that contributes significantly to climate change. In fact, methane has a global warming potential 25 times greater than carbon dioxide over a 100-year period. The release of methane from landfills is a major concern as it amplifies the effects of global warming. It is estimated that landfills are responsible for around 20% of methane emissions worldwide.

Air and water pollution

The decomposition of organic waste in landfills also leads to the release of other harmful gases and substances, contributing to air and water pollution. Landfills emit volatile organic compounds (VOCs), which can react with sunlight to form ground-level ozone, a major component of smog. These emissions can have detrimental effects on human health, especially for individuals with respiratory conditions.

Moreover, when organic waste decomposes in landfills, it generates leachate, a toxic liquid that can seep into soil and contaminate groundwater. Leachate contains a variety of harmful substances, including heavy metals, pesticides, and pathogens, which can pose a threat to ecosystems and human health if not properly managed.

Space consumption

Landfills require vast amounts of land to accommodate the increasing volume of waste generated by society. Organic waste, which makes up a significant portion of municipal solid waste, takes up valuable space in landfills. As urban areas continue to expand, finding suitable land for new landfills becomes increasingly challenging.

Furthermore, landfills can have a negative visual impact on the surrounding landscape, affecting property values and overall aesthetics. The need for more landfills puts additional pressure on communities, as finding suitable sites often leads to conflicts between residents and local authorities.

In order to mitigate the environmental impacts of landfilling organic waste, alternative waste management strategies should be explored. Composting and anaerobic digestion are effective methods for diverting organic waste from landfills and producing valuable resources such as nutrient-rich compost and biogas. Implementing these strategies not only reduces greenhouse gas emissions but also helps conserve valuable landfill space and protects air and water quality.

Alternatives to Landfilling Organics

Landfills have long been the go-to solution for disposing of organic waste. However, with the increasing awareness of the environmental impact of landfills, it has become crucial to explore alternative methods for managing organic matter. Fortunately, there are several sustainable alternatives to landfilling organics that are gaining momentum.


Composting is a natural process that breaks down organic materials into nutrient-rich soil. It involves the decomposition of organic matter by microorganisms, such as bacteria and fungi, in the presence of oxygen. Composting can be done on a small or large scale, making it suitable for both individual households and large-scale composting facilities.

Not only does composting divert organic waste from landfills, but it also produces a valuable end product. The resulting compost can be used to enrich soil in gardens, farms, and landscaping projects. By implementing composting practices, we can reduce greenhouse gas emissions, conserve landfill space, and promote sustainable agriculture.

Anaerobic digestion

An alternative to composting is anaerobic digestion, a process that converts organic waste into biogas and nutrient-rich digestate. Anaerobic digestion occurs in an oxygen-free environment, where microorganisms break down organic materials and produce methane-rich biogas as a byproduct.

The biogas generated through anaerobic digestion can be used as a renewable energy source for heating, electricity generation, or as a vehicle fuel. Additionally, the digestate left behind after the process can be used as a nutrient-rich fertilizer. Anaerobic digestion not only reduces landfill waste but also helps to reduce greenhouse gas emissions and dependency on fossil fuels.

Waste reduction

While composting and anaerobic digestion are effective ways to manage organic waste, the most sustainable approach is to reduce waste generation at the source. By adopting waste reduction practices, such as composting food scraps, avoiding single-use plastics, and supporting local food systems, we can significantly reduce the amount of organic matter that ends up in landfills.

Waste reduction not only benefits the environment but also saves resources and money. It encourages a shift towards a circular economy, where resources are used efficiently, and waste is minimized. By making conscious choices and reducing our waste footprint, we can create a more sustainable future for generations to come.

For more information on composting and waste reduction strategies, you can visit websites such as EPA and Zero Waste Week.


When organic matter like food waste and yard trimmings end up buried in landfills, they are broken down through a complex microbial process known as anaerobic decomposition. While some benefits can arise from landfill gas capture, the methane produced can also escape and exacerbate climate change. Diverting organics through composting, anaerobic digestion, and waste reduction provides a more sustainable waste management strategy. However, even with improving technology and infrastructure, landfills will likely continue receiving organic wastes well into the future.

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