Industry 4.0 technologies, such as additive manufacturing (AM) and blockchain technology, may drive the implementation of a new generation of circular economy strategies. However, the role of these new technologies in designing and implementing circular economy ecosystems is not a trivial issue. In this sense, this PhD research work intended to foster knowledge for the development of industrial symbiosis networks within the AM industry - the so-called additive symbiotic networks. A systematic literature review was performed and revealed current circular economy relationships within the AM industry and highlighted the potential of this industry to create and develop additive symbiotic networks, in plastic wastes from other industries may be used as material inputs for AM processes. A definition of the concept additive symbiotic networks is proposed in this work.

Nevertheless, given the digital nature of AM and considering challenges related to trust or the implementation of transactions within the additive symbiotic networks, there is a need to find tools that enable the development of those networks. Blockchain technology may be an enabler of such symbiotic networks, and its adoption within these settings may have implications in the supply chain of additive symbiotic networks. Using an abductive research approach, in this work two case studies were conducted concerning two additive symbiotic networks, that comprised companies using AM processes to valorize plastic waste streams. Case study A highlighted that there is potential within the context of additive symbiotic networks to explore the adoption of blockchain technology and identified a set of requirements that support the technology adoption in that specific network context. From these conclusions, case study B was developed to understand the implications of adopting such disruptive technology as the blockchain in the supply chain structure of an additive symbiotic network. Results showed that with the adoption of blockchain there is a reduction in the number of intermediary stakeholders involved in the network and there is an adaptation of the value flows within the network.

By offering a tool that helps to deal with the challenges associated with the additive symbiotic networks, exploring its adoption and some of its implications in the supply chain of those networks, this PhD work encourages the development of the additive symbiotic networks, contributing to the efficient use of natural resources, promoting the collaboration between industries, and reducing waste streams to achieve more sustainable production.