A process of "Industrial Symbiosis", which has evolved during the last three decades in the small city of Kalundborg, in Denmark, offers the best evidence that such an approach can be very practical and economically viable. Kalundborg, located 130 km west of Copenhagen, can be seen as a successful example of an industrial complex minimizing pollution and optimizing the use of various resources.

A few industries located there, including a power plant, a gypboard plant, a biotech unit, the fishing activity in the town and the town municipality developed a method of sharing each other's wastes to mutual advantage. The material flows between industries in Kalundborg for the year 1999 are shown in the figure below. Ever since the initial discovery of these interactions in 1989, the economic and environmental benefits along with specific details of resources being shared by industries in Kalundborg has been documented and advocated by the Kalundborg Centre for Industrial Symbiosis. A discussion on Industrial Ecology is never complete without a reference to Kalundborg!