The most advanced estates form a miniature 'industrial ecosystem' in which individual manufacturing processes optimize the consumption of energy and raw materials and the effluents of one process serve as the raw material for another process.
The industrial district of Kalundborg in Denmark is a prime example of industrial symbiosis. For 15 years, industries on the site have exchanged by-products such as surplus energy, waste heat and other materials. In one example, waste heat (in the form of cooling water) from the Asnaes Power Plant provides district heating to houses and buildings in the municipality of Kalundborg.