A natural part of the life cycle, waste occurs when any organism returns substances to the environment.
Communities use a variety of methods to manage wastes depending on the type of waste involved.
The methods used include landfilling, incineration, and composting, with both upstream and downstream separation of usable materials for recycling, especially for incineration. Wastes come from residential, commercial, and industrial sources. According to estimates by the U.S. Environmental Protection Agency, in 1998 we disposed of about 220 million tons of municipal solid waste. Of this, about 55 percent was put in landfills, another 28 percent was recycled or composted, and 17 percent burned. Although waste management in the United States is decentralized and diverse, regulations are promulgated and enforced by the Environmental Protection Agency and similar agencies at the state and local levels.