Solid waste is generally defined as non-soluble material that is discarded in a solid or semi-solid form. This includes garbage, refuse, sludge and other discarded domestic materials, as well as waste from industrial, commercial, agricultural and mining operations.
The U.S. Environmental Protection Agency (EPA) makes a distinction between municipal solid waste and hazardous solid waste. Municipal solid waste, classified by some cities as domestic waste, is composed of everyday items that are discarded after use. These include things such as leftover food, clothing, paper products, appliances, food packaging, yard waste, paint, toys, construction debris and more. The EPA states that Americans generated roughly 251 million tons of trash in 2012, and recycled or composted almost 87 million tons of it. This recycling effort reportedly prevented the release of about 168 million metric tons of carbon dioxide equivalent into the air that year. Solid waste that is not recycled is placed in engineered areas known as landfills, which have built-in protections to keep toxic waste from contaminating groundwater. Hazardous solid waste includes items commonly used in manufacturing and industrial processes, such as solvents, solutions, pesticides, chemicals, pharmaceuticals and petroleum refining residue. Disposal of these products in the United States is strictly regulated by Subtitle C of the Resource Conservation and Recovery Act (RCRA).