A Materials Recovery Facility (MRF) is a specialized plant that receives, separates, and prepares recyclable materials for marketing to end-user manufacturers. There are two different types of MRFs: clean and dirty. A clean MRF takes in commingled recyclable materials that have been separated from municipal solid waste, usually by individual citizens or businesses before curbside trash collection. Although some clean facilities are single stream (i.e., all of the recyclable materials are mixed together), many are dual stream, or source-separated, which means that they receive one stream of mixed paper and one of other materials such as glass, nonferrous metals, and plastics. The recyclables are sorted and then prepared for market. Nonrecyclable or contaminated materials are separated out, but they generally amount to less than 10 percent of the total stream of waste taken in by a clean facility. A dirty MRF takes in a broad stream of solid waste and separates out recyclable materials through manual and mechanical sorting. The recyclables are then processed for market. MRFs play an important role in reducing the waste stream, the demand for raw materials, and pollution associated with the manufacturing of new products.