Mechanical sorting is the separation of waste by machines instead of by hand. Each machine exploits a different physical property: size, weight, shape, magnetism, density or the way a material reflects light.
A typical line uses trommels and screens to sort by size, air classifiers and ballistic separators to split light film from heavy rigid items, magnets and eddy-current separators to remove metals, and optical NIR sorters to identify polymers. Float-sink tanks then separate plastics by density. Mechanical sorting handles large volumes quickly and consistently, which is why it is central to a material recovery facility. It is usually combined with manual sorting for final quality control.
