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Recent research and initiatives increasingly propose a new approach, based on distributed plastic recycling for open-source (OS) 3D printing technologies, as a way to deal with the issue of plastic waste and to support the development of the Circular Economy (CE). Distributed recycling can be thought of as a sort of "smart grid", composed of small and coordinated recycling units. However, the operational complexity of this distributed approach limits its application. Furthermore, the environmental and economic advantages have yet to be demonstrated. This article therefore explores the economic and environmental feasibility of this distributed plastic recycling approach from a logistics perspective, as a step towards its validation. To achieve this, an optimization Mixed Integer Linear Programming (MILP) model was used as an evaluation tool, representing a local Closed Loop Supply Chain (CLSC) network. The proposed model is illustrated using a case study of a university seeking to implement a distributed recycling demonstrator in order to recover 3D printing wastes from secondary schools in the northeast of France. Following this step, a sensitivity analysis was carried out considering the market variations (price of virgin plastic filament) and the amount of available plastic waste derived from the schools. The results obtained show positive economic and environmental benefits of carrying out this new method of plastic recycling. This work serves as a basis for continuing to explore the feasibility and replication of the distributed plastic recycling network in other contexts.

Fused filament fabrication (FFF) is the most common and widespread additive manufacturing (AM) technique, but it requires the formation of filament. Fused granular fabrication (FGF), where plastic granules are directly three-dimensional (3D) printed, has become a promising technique for the AM technology. FGF could be a key driver to promote further greening of distributed recycling thanks to the reduced melt solidification steps and elimination of the filament extruder system. However, only large-scale FGF systems have been tested for technical and economic viability of recycling plastic materials. The objective of this work is to evaluate the performance of the FFF and FGF techniques in terms of technical and economical dimensions at the desktop 3D printing scale. Recycled and virgin polylactic acid material was studied by using five different types of recycling feedstocks: commercial filament, pellets, distributed filament, distributed pellets, and shredded waste. The results showed that the mechanical properties from the FGF technique using same configurations showed no statistical differences to FFF samples. Nevertheless, the granulometry could have an influence on the reproducibility of the samples, which explains that the critical factor in this technology is to assure the material input in the feeding system. In addition, FGF costs per kg of material were reduced to less than 1 e/kg compared with more than 20 e/kg for commercial recycled filament. These results are encouraging to foster FGF printer diffusion among heavy users of 3D printers because of reducing the cost associated to the filament fabrication while ensuring the technical quality. This indicates the possibility of a new type of 3D printing recycled plastic waste that is more likely to drive a circular economy and distributed recycling.

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