Industrial symbiosis is an association between two or more industrial facilities or companies in which the waste or by-products of one become the raw materials for another. This is usually done for both commercial and environmental reasons. It involves a collective approach to competitive advantage through the physical exchange of material by-products. Typical examples of materials sold on to other businesses are shredded tyres, plastic pellets and waste steams from a factory. 

The companies involved may be producing the same things or in completely different sectors. It used to be thought that for industrial symbiosis to work effectively, the companies involved had to be close together. This is no longer the case; although it may not be the best environmental option to transport low-value/grade materials and heat over large distances.

Industrial symbiosis reduces costs and generates new sales for the companies involved, as well as creating significant environmental benefits such as reduced landfill and greenhouse gases. Payback times can vary but typically investments made can be recuperated within three years. The economic activity generated also has further social benefits with the creation of new businesses and jobs.