What is a Dirty MRF?

To anyone that hears the term Dirty MRF (pronounced “murf”) it sounds vaguely unpleasant, maybe even insulting. Perhaps, when you first heard it spoken you thought the person who said it must have been struck by a speech impediment!

A dirty MRF (Materials Recovery Facility) is a waste processing facility, accepting deliveries from WCV (Waste Collection Vehicles), as a mixed solid waste stream (otherwise known as residual waste, or Black Bag waste). The other type of MRF, a Clean MRF, accepts only co-mingled types of materials as collected at the kerbside during the recycled waste collection week for fortnightly waste collection schemes, or in the recycled bins put out in weekly house collection schemes.

The plant and/or labour employed within the plant separates out designated recyclable materials through a combination of manual and mechanical sorting. This often includes a trommel screen and a magnetic separator to remove tins and cans and other metal objects. Also, the sorted recyclable materials may undergo further processing required to meet technical specifications established by end-markets. The remainder, after automatic processing or hand picking, of the mixed waste stream is sent to a disposal facility such as a landfill.

In other words a dirty MRF is one where all the garbage comes into the processing facility and workers sort the recyclable materials from the trash. This type of waste treatment technology accepts refuse and recyclable materials mixed together, and separation occurs within the plant. Recyclable materials which are removed are then sent on to pre-processors and any residual material that is not suitable for processing goes for disposal.

A dirty MRF recovers between five and 45 percent of the incoming material as recyclable materials. The remaining amount is then mostly landfilled, but on some occasions would be otherwise disposed, such as by incineration. However, 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, dirty and clean MRF designs vary significantly.

Processing costs may increase (due to capital costs and the inability to hide labor costs with unpaid homeowners), and sales prices may decrease if the process produces poorer quality recyclables. Process odor may cause significant complaints from local residents if the waste is not treated effectively by a wet scrubber.

Recycling services are available at most dirty MRFs and usually these are located at the entrance to the MRF transfer station area, and newspaper, cardboard, aluminum, tin/steel, plastic and brown, clear and green glass are accepted at the recycling center.

Recycling is about creating new materials from old and these materials have to compete against virgin raw materials. As a result, markets for recyclables fluctuate a great deal, being influenced by the supply and demand for both virgin and recycled materials.

Recyclables are removed via manual and automated sorting. Screened two-inch minus fines (the mixed organic waste fraction) are usually composted with yard trimmings and wood.

Separating and sorting the waste is initially achieved by a combination of the householder and the collection crew, defending on the type of vehicle used for collection and the requirements and capabilities of the MRF.

Such an activity could take place within the towns in any district, perhaps on existing General Employment Areas or land with an employment use. Separators are necessary for those operations that involve both large quantities and multiple types of waste. Limited material flows of one or two types of recyclable materials can be managed by hand sorting and separation.