The term “size reduction” has a number of synonyms in solid waste management, including “shredding” and “grinding”. The term “shredding” has been widely adopted in reference to size reducing mixed waste. In the case of processing source-separated materials, size reduction using granulators and grinders is sometimes practiced for certain types of plastics and for glass, respectively.
Size reduction usually is an essential step in mechanical processing of mixed wastes. The operation reduces bulky items to particles, the sizes of which are compatible with the processing equipment. Size reduction also brings about a degree of uniformity in terms of the maximum particle size of the diverse components or of particle size distribution of the incoming waste stream. This uniformity is a requirement of some mechanical sorting systems [1].
Since source-separated materials typically have a relatively small maximum particle size, a narrow particle size distribution, or both, they do not generally require size reduction prior to entering mechanical or manual sorting systems. In many system designs, some form of size reduction of the sorted materials is exercised after sorting to prepare the materials for marketing.