European Commission, Science for Environment Policy In-depth-report: Indicators for sustainable cities. In-depth Report 12, Vol. 2015, No. 12, p. 24, 2018. 

M. A. Butturi & R. Gamberini, Int. J. of Energy Prod. & Mgmt., Vol. 5, No. 4 (2020) 355-366 

Urban–industrial symbiosis extends the concept of industrial symbiosis, a part of the industrial ecology field, to urban–industrial synergies. Taking advantage of the geographic proximity, it promotes the exchanges of waste, resources, and energy between urban and industrial areas, as well as the sharing of infrastructure.

The I-U S can be considered as an extension of the industrial symbiosis that aims at creating advantageous synergies between firms. According to the United Nations Industrial Development Organization, clustering of industries and the creation of eco-industrial parks promote the development of urban–industrial synergies and allow to reduce the cost of joint infrastructure.

The I-U S concept arose from existing IS projects to fully exploit the advantages of a collaborative approach in reducing the environmental impact at a local level. Due to fast urban development, urban areas generate an increasing amount of waste and they play an important role in water and energy consumption.

The basic concept underpinning the I-U S approach is that urban waste can be delivered to nearby industrial clusters for energy valorisation or recycling, while industries can provide back available extra electrical or thermal energy, avoiding the building of new plants, improving existing plants saturation, and reducing waste landfill.

As the IS can bring benefits to the local communities, allowing to save local resources and reducing waste to be managed by the local infrastructure, the I-U S builds up relationships between cities and local industrial sites that can harmonize the coexistence of living and production areas, improving the environmental, social, and economic sustainability of the whole system.