Materials Recovery Facilities (MRF) are designed to handle a range of recyclables.
These recyclables will have been previously sorted or separated from other waste streams. This might be undertaken by householders and/or employees of waste management companies prior to loading waste onto their vehicles at the kerbside.
The recyclables are taken to MRFs to be separated, sorted and sent onwards for reprocessing and recycling.
As material is normally delivered dry to a MRF, no washing or further processing is usually undertaken on site. Dry recyclables include:
Dry recyclables will therefore exclude organic material (food, garden and wet waste).
Once delivered the dry recyclables are segregated. The degree of segregation required will depend on how the material is delivered. If material is delivered fully or partially sorted, it will be possible to “by-pass” certain elements of the process.
The sorting process in a MRF relies upon on a number of characteristics of the material, such as:
MRF equipment will make use of these characteristics of the material. For example, to separate paper and glass from plastic weight is used.
|Plastic Optical Auto-Sorter|
To sort different types of plastic optical density technologies are used.
The optical sorter measures the plastic composition and then determines where that piece should go. This is done by either letting the plastic fall on to the conveyor below or by blasting it with a jet of air so that it is moved on to another conveyor. Please see the picture.
For metals, magnetism is used to sort the materials.
Within all of these processes there will be a degree of human sorting, typically from a conveyor type operation. This is done to ensure that there are no residual impurities before the material is baled.
Once processed into separate streams the material is then baled, or bulked and transported for onward reprocessing and remanufacturing.
This may not be into the material from which the source came. For example, glass may go to aggregate, and aluminium to vehicle production.
MRFs vary in size, from 50,000 to 200,000 tonnes capacity per annum. Materials suitable for treatment in a MRF typically form 35 per cent of household waste. (Source WRAP)
MRFs will primarily be used to handle packaging residue (bottles, cans, card and plastic).
Most MRFs will not be able to handle organic waste, unless they are integrated into other processes.
MRFs can be owned or managed by local authorities, or established by private businesses to operate in an open market (a merchant MRF).
MRF residues are between 5 and 10 per cent.