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Breaking Down Decomposition: How Food Decays in the Landfill

August 13, 2025

Handful of soil and worms over a blue bucket of compost scraps

Published by Nora Thomas

Understanding the decomposition process and how landfill food waste contributes to climate change 

You have probably heard that food decomposes slowly in a landfill, but do you know why? Let’s look into this muddy process to understand what happens to our food waste, how it returns to the soil, and why it is so important to divert food from the landfill. 

“Breaking Down” Decomposition:

Decomposition describes the gradual process by which raw organic materials break down into simpler substances. This process includes:

  1. Fragmentation – Earthworms and other soil creatures break up material into smaller pieces. This is important because bacteria, which are essential to the decomposition process, can penetrate smaller surface areas more easily.
  2. Leaching – Rainwater dissolves chemicals and nutrients from the organic matter into the soil. 
  3. Mixing – Earthworms and soil organisms mix soil particles and organic materials.

Let’s break this down! Several conditions must be met for this process to occur, and many factors impact the rate of decomposition:

Oxygen

There are two main types of decomposition – anaerobic and aerobic. Aerobic decomposition occurs when oxygen is available. This includes most examples in nature, like a leaf decomposing on the surface of the forest floor. Contrastingly, anaerobic decomposition occurs in the absence of oxygen, typically underground or in compressed environments. This means that decomposers that require oxygen cannot support the process. Although anaerobic decomposition does occur in nature, aerobic decomposition is more common and much faster. 

Nutrients

Soil organisms break down complex nutrients and turn them into simpler substances, such as water, carbon dioxide, and bioavailable nitrogen, phosphorus, and calcium. When the soil organisms die and decompose, these nutrients become available to other organisms. Without decomposers, plants would struggle to find available nitrogen, which they cannot grow and function without.

Temperature

Temperature is critical to the decomposition process, especially when it comes to decomposers. Some microorganisms prefer medium temperatures, around 50-113°F, and are present at the beginning of the process. These are called mesophiles. Thermophiles, on the other hand, prefer warmer temperatures around 113-158°F, and appear 5-10 days into the decomposition process. Mesophilic and thermophilic organisms are typically bacteria, archaea, or eukarya.

In general, cold temperatures slow decomposition, and warm temperatures speed up the process. High temperatures are also important because they inhibit weeds, diseases, and seeds, which pose threats to the process.

Moisture

Proper moisture is necessary to support microbial organisms that play a key role in decomposing the organic matter. On the other hand, if there is too much water, oxygen can be limited, which constricts the decomposition process.

Decomposers

While we can often see earthworms, the nearly invisible fungi, protozoa, and bacteria are also critical soil organisms that break down organic matter. They are found more in aerobic than anaerobic decomposition. Mesophilic and thermophilic bacteria start the process. Then, as the temperature lowers towards the end of the process, actinomycetes and fungi work on the outer surface.

small mushrooms on soil
Mushrooms decomposing in soil

What Happens When Our Food Goes to the Landfill?

Now that we’ve looked into how organic materials decompose in nature, we can understand how the decomposition process is different in a landfill environment. 

The food decomposition process is delayed in a landfill environment because the ideal conditions required for decomposition are not met. Primarily, landfills use bulldozers and compactors to fit as much waste as possible. This compaction limits oxygen and organism diversity, making aerobic decomposition impossible. 

Plough on landfill site
Plough on a landfill site

Anaerobic decomposition is possible through organisms such as bacteria and archaea; however, it results in harmful greenhouse gas emissions. As these organisms break down organic matter in the absence of oxygen, they release methane gas. Methane-producing microbes are not active when oxygen is present, which is why aerobic digestion is not as environmentally harmful. 

According to the EPA, methane makes up 11% of global carbon emissions and is over 28 times as potent as carbon dioxide, which means it has a much greater capacity to trap heat in the atmosphere. Food waste represents 24% of all municipal waste and accounts for 58% of all methane generated in landfills. This large release of potent greenhouse gas demonstrates that food decay in the landfill is a major contributor to climate change.  Finally, we generally underestimate how long it takes for our food waste to decay, and this process is further delayed in a landfill environment. For example, a head of lettuce may take 2-3 weeks to decompose in a compost bin, but take up to 25 years to fully decompose in a landfill. The difference is shocking!

Why Does This Matter?

According to the USDA, 30-40% of all food in the United States ends up in the landfill. Furthermore, in 2023, only 6.08% of all food and yard waste generated in the United States was composted. Out of all of the municipal solid waste generated in the US, 21.59% represents food, which is equivalent to 63.1 million tons. This means that 63.1 million tons of food are sitting in the landfill, taking up space, and producing greenhouse gases, when they could instead be undergoing the natural decomposition cycle and returning nutrients to the Earth. Understanding how much waste is produced is especially startling considering how many individuals are experiencing hunger and food insecurity.

EPA Methane Graphic - "Wasted food causes 58% of methane emissions from municipal solid waste landfills"

These drastic statistics also serve as a reminder that food insecurity does not stem from a lack of food but rather unequal distribution and overwhelming waste. 

What Can We Do?

The answer is clear – we must divert as much food from the landfill as possible to decrease food waste and environmental impact, and increase food accessibility. 

The solution starts with preventing food waste by only buying and serving what you need. Before you throw food away, think about what you can do instead of sending it to the landfill! If the food is not spoiled, you can upcycle it or donate it. If that option is no longer viable, you can turn wasted food into animal feed. Although hopefully avoidable, the next step is composting. Following these steps should limit nearly all food waste from landfills.

We recommend following a food waste scale or food recovery hierarchy, like this one from the EPA: 

EPA Wasted Food Scale - How to reduce the environmental impacts of wasted food.

Understanding why food waste in the landfill is so harmful can better inform our actions. The amount of food sent to our landfills is shocking, especially considering the prevalence of food insecurity and the environmental harm caused by food in the landfill. Now that you understand the impact of your waste, ask yourself what you can do to reduce it!

Make an Impact:

  1. Get Involved: Join our volunteer team here at We Don’t Waste to help redistribute food! 
  2. Reduce waste in your home by making conscious shopping and food storage choices. 
  3. Start Composting: Set up compost in your backyard or schedule a pickup service!
  4. Stay Informed: Follow us on Instagram, Facebook, and TikTok to learn more about food recovery and stay up-to-date on our latest events!