A material recovery facility or material reclamation facility (MRF) is a specialized plant that receives and separates recyclable materials from a waste stream. The plant configuration for a WTE project starts with a MRF. By removing the material that can be recycled (i.e. metals and glass) along with other inert components (i.e. sand and dirt), the raw municipal solid waste (MSW) is processed into refuse derived fuel (RDF) pellets. Using RDF instead of raw MSW makes our energy projects more efficient because we do not heat up the “extra” inert materials that are only to be rejected with the ash. There are two major types of MRF plants, the Clean MRF and the Dirty MRF.
A Clean MRF accepts commingled recyclable materials that have already been separated at the source from municipal solid waste generated by either residential or commercial sources. There are a variety of clean MRF configurations with the most common being single stream, where all the mixed recyclable material is processed through the same series of separation steps. An alternative configuration is a dual stream MRF, where source-separated recyclables are processed through different steps depending on the type of materials delivered (i.e. metals or plastics). Once the desired recyclable (and inert) materials have been separated, the remaining materials are shredded and densified to use as RDF for our WTE projects.
A Dirty MRF accepts a mixed solid waste stream and then proceeds to separate out designated recyclable materials through a combination of manual and mechanical sorting. The sorted recyclable materials may undergo further processing required to meet technical specifications established by end-markets users, while the balance of the mixed waste stream is shredded and densified and then used as RDF to power our conversion technology.
The Large, The Small, The Clean And The Dirty: Equipping MRFs
Erik E. Colville and Nancy J. McFeron
A materials recovery facility, or MRF, by any other name, would still be either clean or dirty. Of course, sorting recyclables is a dirty business, but the terms «clean» and «dirty» refer to the method of collection while the type of MRF is determined by a community’s needs.
Clean MRFs handle commingled or pre-separated recyclables from curbside collection programs, drop-off sites or satellite recycling centers. Dirty MRFs process recyclables from a stream of raw solid waste and are sometimes used in areas with no curbside programs or in communities that are not interested in recycling. Selecting facility size, configuration and equipment differs greatly for the two basic types of MRFs, and it’s important that the consultant recognizes these differences when designing a MRF.
A small, clean MRF processes less than 50 tons per day of recyclables and a large facility processes 200 to 300 tons per day. A small, dirty MRF processes less than 200 tons per day of mixed municipal solid waste and a large facility processes more than 700 tons per day.
More than 90 percent of the material entering a clean MRF is processed and made ready for sale. A dirty MRF recovers between five and 45 percent of the incoming material as recyclables, then the remainder is landfilled or otherwise disposed. Because the material entering a clean MRF typically weighs 50 to 100 pounds per cubic yard and the material entering a dirty MRF weighs about 350 pounds per cubic yard, MRF designs vary significantly.
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