*3.1. Existing IS Projects on a Cross-Country Level*

The functioning of ecosystems due to industrial symbiosis can be represented as an eco-network in which materials circulate, the economic value of which increases, and the economic activity itself is directed towards zero waste and, as a result, reduces the anthropogenic impact. Industrial symbiosis in different countries pursues the same goal related to the realization of not only economic benefits but also environmental benefits through the circular exchange of resources, but also, in recent times, through smart specialization.

Smart specialization is being developed by the European Commission as one of the strategies for achieving the SDGs based on the methodologies of combining science, technology, and innovation. The key to the implementation of industrial symbioses is public–private partnership for the sustainable development of production in the transition to a circular economy based on the use of recycled materials in production and the use

of green technologies in value chains that use fewer natural resources. It is in industrial symbiosis ecosystems that efficiency depends on the optimal use of resources (locating on the same production site; sharing production infrastructure; use of waste or by-products) and at the same time producing less waste and CO2, which allows the parties involved to receive additional income by reducing production costs and reducing environmental taxes [59–61].

The main projects by region are presented in Table 1. The authors decided to limit the projects to the EU, as according to recent research [62], the EU is leading in number of publications and practical projects in the field—with 48 studies published (Table 1), followed by China with 12 and the USA only 5. In developing countries, the potential for involving secondary resources in the industrial symbiosis of enterprises is not fully used, which is associated with the capacities of the production infrastructure.
