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2.5 Topic e: Landfills

Landfilling is still the primary means of managing solid waste in North America, handling about 65- 70% of MSW. This represents a significant decrease since the late 1980s, when landfills were used to manage over 80% of MSW. While the fraction of MSW that is landfilled has declined slightly over the past few years, the total amount generated continues to increase, resulting in a gross increase in the amount of MSW that is landfilled. MSW landfills in the US are allowed to accept only non- hazardous solid waste, such as household garbage, except for small quantities of residential and commercial hazardous waste exempted from hazardous waste management laws.

Although there are approximately 3,500 MSW landfills operating in the US alone, this represents a significant decline since environmental regulations on landfills, including a ban on open dumping, were first issued in 1979. Recent regulatory requirements expanded on those first issued in 1979, so that landfills must now meet strict design and operating requirements designed to minimize hazards to public health and the environment. As many landfills have approached the end of their useful lives and local officials encounter the problem of siting new landfills, some communities have been faced with a serious landfill "capacity crisis." This has already occurred in many areas, particularly in the Northeast and the Midwest.

Partly in response to this situation, fewer but larger, more environmentally sound, regional landfills ("megafills") are being built to handle waste disposal needs. These new landfills, which provide considerable low-cost capacity, are designed to comply with stricter federal and state regulations and are being built in part via private sector investment. Siting of regional landfills can be difficult, however. In the Toronto area, for example, the siting process for new landfills became such a contentious issue that responsibility was taken away from the local and regional governments in 1991, and a separate body, accountable to the provincial government, was established. This body has since been disbanded, and the area is still without a new landfill site.

MSW landfills, either old or new, can pose threats to human health and the environment. The greatest concern is the potential for contaminants from a landfill to pollute valuable ground water or surface water supplies. In addition, accumulated quantities of landfill gas can pose the threat of explosion. A state-of-the-art landfill in North America contains sophisticated engineering features to prevent the release of hazardous substances to the environment, including liners, leachate collection, final covers, and other features.

Natural or synthetic materials are often used to line the bottom and sides of landfills to prevent the migration of leachate into nearby ground water and surface water. Leachate retained by the liner will accumulate and possibly leak through the liner unless it is removed by a leachate collection system. Leachate collection systems are installed above the liner and usually consist of a perforated piping system which collects and carries the leachate to a storage tank. Final covers are placed over closed landfills to prevent the infiltration of rain and other sources of water, thereby minimizing the production of leachate. Some landfills in the US now reinject leachate into the landfill to speed biodegradation. This process is discussed further in the Sound Practices section.

Additional operating requirements typically include the exclusion of hazardous waste; control of disease vector populations; monitoring of methane gas production; restriction of public access; construction of run-on and run-off controls; protection of surface water from pollutants; and maintenance of compliance records. Landfill gas can be recovered as a source of energy at landfills that generate sufficient quantities of methane. The technology necessary to recover landfill gas is proven and commercially available. Over 150 landfills located throughout the US currently recover methane gas.

If ground-water or surface-water contamination, explosive gas emissions, disease vectors, or other environmental problems exceed acceptable standards, corrective actions are required in order to remedy the problem. Specific actions taken vary depending on the particular case, but typically will include many of the same elements described above (e.g., landfill cover, leachate collection and treatment, landfill gas collection), albeit in an improved fashion if previous designs failed. Landfills that cannot meet environmental standards must close, and in most cases must meet closure and post- closure care requirements to ensure protection of human health and the environment.

About 10% of the approximately 1,200 sites on the US "Superfund" list of hazardous waste sites are former MSW landfills. The vast majority are old landfills that are on the list because in the past they accepted quantities of industrial hazardous waste along with MSW. Cleanup of these sites must meet very strict standards costing an average of US$25 million per site. Remedial activities can include on-site or off-site incineration, and off-site disposal at a hazardous waste management facility. Similarly, Canada is experiencing the same problem in redressing past waste management practices and mistakes. In the province of Ontario, 28 hazardous waste "hot spots," or toxic waste sites, have been identified. They are abandoned landfill sites now requiring federal or provincial funding for clean-up.

Landfill mining is the process of recovering buried resources by literally digging up, or mining, a facility to recover compost, recyclable materials such as aluminum, glass, and plastics, and combustible materials that can be used as fuel for WTE facilities. Landfill mining is relatively new, but like other MSW management options, the feasibility of landfill mining will depend on site-specific circumstances and can involve environmental risks, such as disturbing old hazardous waste drums.

Landfills in North America are seen as a necessary component of any integrated MSW management system. Although recycling and composting can divert a significant portion of MSW from landfills, not all MSW is recyclable or compostable. Likewise, although waste-to-energy technologies can significantly reduce the volume of MSW, all WTE facilities produce residual ash that must be landfilled. In addition, as WTE facilities are shut down for repairs or maintenance, MSW will have to be diverted to landfills.

Table of Contents

• Brochure
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• International Year of Forests
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• World Environment Day
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• UNEP Campaign
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