The major purpose of sanitary landfills, which are the most common waste management technology employed in the United States(1), is the storage of MSW in a way that protects human health and the environment. This section reviews two types of landfills:

All MSW management technologies addressed in this report require landfills for their residues, and the amount of that residue is affected by the technologies used to extract materials and energy from the waste. Even recycling requires landfills to dispose of: the impurities separated in materials recovery facilities (MRF) or later at smelters (i.e., slag); paper sludge containing fiber that is too short for reuse; fillers and inks; or small pieces of mixed-color glass. In general, recycling delays and/or reduces requirements for land disposal rather than eliminating them.


Design of Sanitary Landfills

A new sanitary landfill is subject to many design regulations set by the U.S. Environmental Protection Agency (EPA) under "Guidelines for the Land Disposal of Solid Waste" (CFR, l991b), by states, and by local communizes. All new landfills that accept more than 20 tons of MSW per day are subject to requirements for controlling emissions to groundwater. Because all landfills that contain wet organic material produce methane, the largest of such landfills are likely to have to meet additional existing and proposed requirements for controlling emissions into the air.

State-of-the-art landfills incorporate a liner system, a leachate collection system, a leachate treatment system, a cap system, gas recovery systems to recover energy or to flare the gas, landscaping, security, groundwater monitoring wells, and a groundwater plan. The landfills require about 30 years of postclosure monitoring, care, and planning for eventual community use.

One of the most critical parts of the design is the liner at the bottom of the landfill (CEC, 1991). Figure 6.1 illustrates a design that conforms with current regulations. Regulations require that during operations the new MSW must be compacted and covered daily with an inert material that prevents litter from blowing and from providing a refuge for animals and insects. A cross-section of an approved liner design is shown in Figure 6.2. Appendix F provides a more detailed description of the requirements for constructing and operating landfills.

All new landfills that accept more than 20 tons per day of MSW must, in accordance with EPA regulations, collect and dispose of leachate and minimize the infiltration of water. Reducing water content retards biodegradation, and as a result the conversion of organic waste to methane and CO2 is inefficient. Rathje indicates that landfills preserve waste for future generations (Rathje, 1989; Rathje, 1990), and Bogner and Spokas report preliminary evidence that landfills are providing a sink for carbon by removing it from the atmospheric CO2 cycle (Bogner and Spokas, 1992).

Figure 6.1


Figure 6.2

Click here to expand figure.

Operating Characteristics

Landfilling combines preservation of waste, low-temperature partial oxidation and reduction through biological activity, and limited dissolution of components in the waste. Traditional landfilling operations consist of a daily cycle of filling, compacting the fill with heavy equipment, and covering the fill with "earthen materials" (CFR, l991c).

Variations on this traditional method, as summarized below, are also being considered (see Appendix F for more detailed descriptions):

Commercial Status


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