Landfills are disposal sites for solid waste. There are approximately 3000 active landfills in the United States, with another 10,000 that are no longer in use. Modern landfills are engineered to protect the surrounding environment from leaching and degradation. In 2007, the U.S. produced about 254 million tons of waste, and we were able to recycle or compost about 85 million tons of this, for a diversion rate of about 33 percent. About 32 million tons were combusted for energy recovery, leaving about 137 million tons, or 54 percent of our total waste, which was disposed of in landfills.
http://www.pollutionissues.com/Ho-Li/Landfill.html
http://www.epa.gov/waste/nonhaz/municipal/index.htm
http://www.epa.gov/epawaste/nonhaz/municipal/pubs/msw07-fs.pdf