scope:

BACKGROUND

According to recent studies, the United States generates some 545 million tons of non-hazardous waste per year, of which almost 70 percent is disposed of in landfills. Regulations promulgated under Subtitle D of the Resource Conservation and Recovery Act (RCRA) require municipal solid waste (MSW) landfills to be protective of human health and the environment. In order to meet the RCRA requirements, landfills are designed with impermeable liners and leachate collection systems to prevent groundwater contamination, a low permeability cap to prevent liquid intrusion after closure, and a landfill gas extraction system to prevent air emissions. In addition, owners are required to maintain the landfill for 30 years or more after final closure and provide financial assurance for these activities.

One of the major concerns addressed by the RCRA requirements was to minimize the potential for groundwater contamination. This approach resulted in MSW landfills becoming "dry tombs" (i.e., lacking water). However because of moisture limitations, the biodegradation of the organic material by bacteria in an MSW landfill proceeds at a very slow rate.

Despite being able to provide environmental protection, the "dry tomb" landfill has many drawbacks including:

• The production of leachate and air emissions for an extended time period that must be monitored, controlled, and treated;

• An extended post-closure care period because of waste settlement (i.e., the final cap settles as waste decomposes); and

• A decreased landfill life because landfills are typically permitted to accept a set volume of waste.