Circular Cities: determinants of closed circulation of building materials.

In 2030, cities will be inhabited by 80% of the human population. The urban metabolism of cities is constantly increasing as well as the material-consumption of urban areas. The amount of waste rises. Construction waste constitutes a significant fraction in the global waste stream - 10-15% of all waste and 34% in Europe. Moreover, it is estimated that further extraction of materials from natural resources will provoke a three-fold increase in raw material consumption by 2050. Therefore, future, intelligent urbanization requires a new approach to urban systems, which would integrate the issue of minimised consumption of raw materials and sustainable management of construction waste with urban planning and building design. Closed circulation of building materials in urban areas depends on economic, environmental, social and infrastructural determinants and is related to the amount of waste. The understanding of the decisive determinants of building materials’ circulation within a city shows the importance of sustainable practices in urban planning, architectural design and construction process, which should be integrated with adequate pro-environmental policies, economic incentives, educational programmes and open-access data systems. Only cross-sectoral, multi-level actions, which are based on profound analysis of decisive factors, can enable circular material flows in the cities.