Automated garbage sorting techniques can be categorized into two types: direct sorting and indirect sorting. Direct sorting techniques utilize material properties like magnetic susceptibility, electrical conductivity and density for heavy media separation by applying external fields like magnetic, eddy current and gravity respectively. Indirect sorting, on the other hand, employs sensors to detect the presence and often the location of recyclables in the waste so that automated machines or robots can be employed to sort the detected recyclable materials.
The entire process flow of automated sorting of recyclable materials from MSW. Initially, pre-treatment is performed using screw press, disc screen, and shredder + magnetic techniques. After this, dry waste is obtained and later dry waste fraction is subjected to comminution or shredding processes that include swing-hammer shredder, rotating drum, alligator shears, hammer mill, ring mill, shear shredder and impact crusher-based techniques. In order to sort ferrous materials, magnetic drum techniques are used. After this, non-ferrous metals are sorted using various indirect sorting techniques like eddy current and optical sort.