Environmental Impact of Landfills

Landfills are essential infrastructure, but they carry environmental risks that require ongoing management. Modern engineered landfills dramatically reduce these impacts compared to legacy dumps, but no landfill is completely inert. Here are the key environmental concerns and how they are managed in Canada.

Leachate Contamination

Leachate — the liquid that forms when water filters through waste — is the most significant environmental risk from landfills. It can contain heavy metals (lead, mercury, cadmium), organic compounds (benzene, vinyl chloride), ammonia, and pathogens. If leachate escapes the liner system and reaches groundwater, it can contaminate drinking water supplies for decades. Modern landfills prevent this through composite liner systems, leachate collection networks, and groundwater monitoring wells. Canadian regulations require groundwater testing at least semi-annually at all active and recently closed landfills.

Methane and Greenhouse Gas Emissions

Landfills are a major source of anthropogenic methane — responsible for approximately 20% of Canada's methane emissions. Methane is 25-28 times more potent as a greenhouse gas than CO₂ over a 100-year period. The decomposition of organic waste (food, paper, wood, yard waste) in anaerobic conditions produces landfill gas. Modern landfills capture this gas through well networks and either flare it (converting methane to less harmful CO₂) or use it for energy generation. Some Canadian landfills now upgrade landfill gas to renewable natural gas (RNG) and inject it into provincial gas grids. Despite these efforts, a significant portion of methane still escapes — particularly from older and closed facilities.

Groundwater and Surface Water Risk

Beyond leachate, landfills can affect water quality through sedimentation, altered drainage patterns, and surface water runoff. Stormwater that contacts the working face of the landfill can carry contaminants into nearby streams and wetlands. Regulations require diversion of clean stormwater around active landfill areas and treatment of any water that contacts waste.

Air Quality and Odour

Landfills emit hydrogen sulfide (H₂S), volatile organic compounds (VOCs), and particulate matter. H₂S produces the characteristic “rotten egg” smell, and while not typically present at harmful concentrations beyond the property boundary, it is the most common source of community complaints about landfill operations. Modern odour management includes daily cover, gas collection systems, odour-neutralizing misting systems, and buffer zones between the landfill and residential areas.

Land Use and Remediation

Landfills occupy significant land area — often hundreds of hectares for major urban facilities. Once closed, the land requires decades of post-closure monitoring and maintenance before it can be safely repurposed. Successful remediation projects across Canada have transformed closed landfills into parks (Riverdale Park in Toronto), golf courses, wildlife habitats, and even solar farms. The key to successful reuse is proper closure engineering: a stable cap, functioning gas and leachate systems, and thorough monitoring.

Modern Approaches

Canada is increasingly adopting waste diversion strategies that reduce landfill reliance: organics composting, extended producer responsibility (EPR) for packaging and hazardous materials, and circular economy initiatives. These efforts have already reduced per-capita waste disposal in several provinces. Engineered landfills remain necessary for the foreseeable future, but improvements in design, operation, and post-closure care continue to reduce their environmental footprint.