Waste sorting facilities, together with collection infrastructure, act as a filter in the waste management chain, extracting more or less finely sorted material fractions that can be diverted directly into manufacturing or sold as commodities on the local or global market, and reducing the quantity of waste for final disposal. Waste sorting plants sit between collection infrastructure on one side and material markets and disposal on the other: they must be designed and implemented with consideration to both. The exact configuration of a sorting plant is largely dependent on the planned input, the desired output, and the level of technology and financing available. Waste sorting facilities demand a critical and steady mass of input waste material to be financially viable. A shortfall in input waste means both a drop in gate fees and a reduced quantity of output material to sell. As such, they are often extra municipal or regional, serving multiple municipalities from a central location to ensure long-term economic viability.
Waste sorting facilities receive waste from collectors and process this waste in a number of stages. The result is one or more clean material fractions for recycling or further sorting, and a residual component for disposal – typically incineration or land filling. The configuration of sorting facilities varies from simple manual sorting lines to complex, automated multi-process sorting lines. The sorting process lies at the core of the waste sorting plant, but is supported by a number of pre-input and post-output ancillary processes that enable the smooth running of the facility. Positive vs. negative sorting There are two different conceptual approaches to sorting waste: positive sorting and negative sorting. Positive sorting focuses on identifying and removing a desired fraction from the input waste stream (i.e. eddy current which targets specifically nonferrous materials). Negative sorting focuses instead on identifying and removing a non-desired fraction.
