Landfill Odours
Understanding Landfill Odours
Sometimes people notice smells coming from landfills or composting sites. These odours can be unpleasant, but they are a normal part of how waste breaks down over time.
Knowing where the smells come from—and why they sometimes seem the same—can help everyone understand what’s happening and what Claystone is doing to manage it.
Landfill and composting odours may sometimes smell similar, but they come from different sources. Landfills create odours deep underground where there is no air, while composting odours usually happen when piles need more air or less moisture.
Claystone continues to monitor, manage, and reduce odours to keep our community clean, healthy, and comfortable for everyone.
View the Claystone Odour Reports
Where Landfill Odours Come From
Landfills hold regular household and commercial garbage, called municipal solid waste (or MSW). This includes things like food scraps, paper, yard waste, and packaging.
When these materials start to break down, they give off gases. Because landfills are packed tightly and don’t have much air inside, the breakdown happens without oxygen (this is called anaerobic decomposition).
This process can create gases that have strong smells, such as:
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Hydrogen sulfide, which smells like rotten eggs.
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Methanethiol and dimethyl sulfide, which can smell musty or sulfur-like.
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Other organic gases, which may have sweet or chemical odours.
These smells can sometimes be stronger on hot or humid days, or when the wind is blowing from the landfill toward nearby homes.
Where Composting Odours Come From
Composting is a different process. It’s designed to turn food scraps, leaves, and other organic materials into a soil-like product that can be used in gardens and landscaping.
Composting usually happens with oxygen (this is called aerobic decomposition), and when it’s working properly, it smells earthy—like soil or a forest floor.
If the compost pile gets too wet or too tightly packed, it can lose air. When that happens, the process turns anaerobic, just like in a landfill. That’s when similar “rotten egg” or “decaying” smells can occur.
So even though landfills and composting sites are different, they can sometimes smell the same because the same types of gases form when organic materials break down without enough oxygen.
How odour travels from compost facilities
How Claystone Manages Odours
Both landfills and composting sites use special methods to reduce odours, such as:
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Covering landfill areas daily to trap odours inside.
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Collecting and treating landfill gases before they reach the air.
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Turning compost piles often to keep oxygen flowing.
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Controlling moisture levels to prevent anaerobic conditions.
Claystone staff also conducts daily odour checks around the perimeter of our site, which includes monitor weather and air quality, and respond quickly if odours become noticeable in the area.
Odour Concerns
Claystone Waste is committed to being a good neighbour and we take odour concerns very seriously.
If you are noticing odours that are problematic, please complete our Odour Issues – Customer Service Opportunity Form. This form will ask you for important information that will assist us in identifying the cause of the odour and making any necessary adjustments.
Please note that forms submitted outside of office hours will be addressed as soon as possible.
