As an abundant commodity, coffee production generates significant scraps and by-products, increasing the potential pollution hazards. Circular economy and bioeconomy can help valorize Spent Coffee Grounds (SCGs), e.g., as fillers in polymer-based composites using conventional manufacturing, i.e., injection molding. Large-format additive manufacturing with pellet extruders offers a further option for new applications, reducing costs for the valorization of biomass waste. However, its use in this context remains unexplored, especially for applications with complex geometries or critical overhangs. This work investigates new biomass waste-based materials for large-format additive manufacturing with direct feeding extrusion, fabricating self-supported complex overhang geometries through nonplanar slicing. The thermal, rheological, and mechanical properties of three novel polymer-based pellet compounds with post-industrial SCGs, i.e., injection molding grade polylactic acid/SCGs, recycled low-density polyethylene/SCGs, and high-density polyethylene/SCGs, were herein investigated to evaluate their printability, defining their extrusion temperatures (190 °C and 170 °C). Results showed suitable viscosity ranges (133.6–839.7 Pa∙s) and accurate tensile values comparable with literature, e.g., 1–3% minimum relative standard deviations (polylactic acid/SCGs), or conventional manufacturing, e.g., elastic moduli of 107.4 MPa (recycled low-density polyethylene/SCGs) and 587 MPa (high-density polyethylene/SCGs). Their use with large-format 3D printers was assessed thanks to nonplanar samples with complex overhang geometries, reaching a maximum curvature angle of 32° and fabricating overhangs up to 25° without supports. According to the tests, especially polylactic acid/SCGs, a bio-based compound, and recycled low-density polyethylene/SCGs, a fully recycled material, can be used for large-format 3D printing applications with complex geometries, e.g., furniture, interior, and exhibition design. This work paves the way for new materials for large-format additive manufacturing, reducing the need for 3D printing grade feedstock, cutting costs and consumption from filament processing, and fostering material waste reduction practices.
@journalarticle{romani2024Coffee,title={Large‑format material extrusion additive manufacturing of PLA, LDPE, and HDPE compound feedstock with spent coffee grounds},author={Romani, Alessia and Paramatti, Martina and Gallo, Laura and Levi, Marinella},journal={The International Journal of Advanced Manufacturing Technology},volume={134},pages={1845–1861},numpages={17},year={2024},publisher={Springer},doi={10.1007/s00170-024-14214-2},url={https://doi.org/10.1007/s00170-024-14214-2},keywords={3D printing, Bio-based polymer compound, Fused Granular Fabrication, Fused Filament Fabrication, Circular economy, Nonplanar slicing},}
Circularity by design, materials and additive manufacturing. Fostering sustainable and circular materialities enabled by additive manufacturing
New sustainable production models are gaining attention to reduce the human impact on Earth in the next few years. Design practices, materials, and digital fabrication tools, i.e., additive manufacturing, play a crucial role in this local and global change. A comprehensive range of circular materials and design strategies can be implemented to foster the development of new products and applications following circular economy principles. Nevertheless, their current exploitation in practical contexts is still challenging. Designers, engineers, and practitioners are not always aware of the possibilities allowed by these materials and how to use them in real projects. At the same time, their potential applications and experiential aspects are scarcely considered in the conventional materials development process. In contrast, new production and consumption patterns based on additive manufacturing arise from local communities and distributed networks. This Ph.D. research explores the interconnections between design, materials, additive manufacturing, and circular economy. The goal is to stimulate the use of new circular materials and strategies in real contexts by investigating possible materials and applications. At a later stage, it aims to foster knowledge building and transfer processes on these topics by developing accessible and participative experiential tools for designers, professionals, and students. The study adopts a transdisciplinary approach merging the materials engineering and design disciplines, mainly product design and engineering design. The research comprehends case study analysis, materials characterizations, design experimentations (Research through Design), product development, and reflective practice. It mainly focuses on two case studies, dealing with specific secondary raw materials and investigating new circular materials, additive manufacturing technologies, plausible design strategies, and applications in collaboration with professionals, industries, and labs. The first case study, FiberEUse, is linked to recycled glass and carbon fiber-reinforced polymers, mainly thermosetting, for small-format 3D printers. The second case study, RepMat, deals with recycled thermoplastics and biomass scraps or by-products in large-format 3D printers. The experimental activities resulted in a set of new circular materials, modified 3D printing systems, and potential applications, e.g., in furniture, automotive, and sports sectors. A novel, accessible, and replicative experiential tool based on the concept of materials libraries, the “Materials Library System”, was developed to share and build new knowledge on circular materials for additive manufacturing, fostering collaborative distributed networks. This open source tool, made of a physical and virtual part, can showcase new materials (divulgative use) or guide the investigation of emerging materials and technologies in different contexts, i.e., labs, makerspaces, and studios (experimental use). The experimentations outlined the contribution of specific design professionals, i.e., materials designers and engineering designers, to exploit circular materials for additive manufacturing in real contexts. Finally, the research redefines the role of materials libraries in the current scenario, contributing to the democratization process of materials and technological knowledge for and through design.
@thesis{romani2024PhD,title={Circularity by design, materials and additive manufacturing. Fostering sustainable and circular materialities enabled by additive manufacturing},author={Romani, Alessia},journal={Ph.D. thesis, Politecnico di Milano},year={2024},url={https://www.politesi.polimi.it/handle/10589/217101?mode=complete},keywords={circular economy, additive manufacturing, materials library, materials for design, materials design, engineering design, open design}}
Characterization of PLA feedstock after multiple recycling processes for large-format material extrusion additive manufacturing
Alessia Romani, Lorenzo Perusin, Mattia Ciurnelli, and
1 more author
Since the take-make-dispose model is leading to significant waste production and environmental impact, circular economy models have been spreading to reduce waste and resource depletion, rethinking the existing resource cycles. Plastic waste created environmental and economic concerns, requiring new recycling methods and strategies to preserve resources. This practice plays a key role in extrusion-based additive manufacturing, converting waste into recycled feedstock. Large-format additive manufacturing represents a promising way to scale up recycling strategies with granulated polymer feedstock, especially considering popular materials, i.e., PLA. However, thermomechanical degradation affects the quality of this secondary raw material, and these effects on large-format systems are scarcely studied. This work investigates the thermal, rheological, and mechanical properties of PLA feedstock for large-format additive manufacturing after multiple recycling processes, i.e., up to six. The effect of material degradation from multiple recycling processes was assessed through Gel Permeation Chromatography, Differential Scanning Calorimetry, flow stress ramp tests, tensile tests, and colorimetry. Some 3D printed parts were fabricated to assess the overall quality of the process, including pieces from potential applications. Lower effects of thermomechanical degradation were found compared to desktop-size 3D printers, mainly by cutting the reprocessing steps to produce secondary raw materials, i.e., making new filaments. Recycled granulate PLA feedstocks represent a potential alternative to virgin pellets for new applications in real-world contexts.
@journalarticle{romani2024rPLA,title={Characterization of PLA feedstock after multiple recycling processes for large-format material extrusion additive manufacturing},author={Romani, Alessia and Perusin, Lorenzo and Ciurnelli, Mattia and Levi, Marinella},journal={Materials Today Sustainability},volume={25},pages={100636},numpages={16},year={2024},publisher={Elsevier},doi={10.1016/j.mtsust.2023.100636},url={https://www.sciencedirect.com/science/article/pii/S2589234723003238?via%3Dihub},keywords={3D printing, Fused Filament Fabrication (FFF), Fused Granular Fabrication (FGF), Recycling, Polylactic acid (PLA), Distributed recycling for additive manufacturing (DRAM)}}
PLA Feedstock Filled with Spent Coffee Grounds for New Product Applications with Large-Format Material Extrusion Additive Manufacturing
Martina Paramatti, Alessia Romani, Gianluca Pugliese, and
1 more author
Food waste and loss generate significant waste such as spent coffee grounds (SCGs) from coffee consumption. These byproducts can be valorized by following circular economy and bioeconomy principles, e.g., using SCGs in polymer-based composites for 3D printing. Although desktop-size material extrusion additive manufacturing is increasingly adopted for biomass-polymer-based composites, the potential of large-format direct extrusion 3D printing systems remains unexplored. This work investigated the thermal, rheological, and mechanical properties of PLA/SCG composites for applications with a large-format pellet extrusion 3D printer. The formulations exhibit minimal degradation at typical 3D printing temperatures of PLA, i.e., ∼190 °C, and limited effects on crystallinity by increasing the SCG weight percentage. The decrease in viscosity due to SCGs improves the printability and layer adhesion, as confirmed by the tensile test results, such as higher ultimate tensile strength and elongation at break values compared to those of the state-of-the-art values. Using pellet feedstocks contributes to limiting the effects of thermomechanical degradation by reducing raw material processing, i.e., avoiding filament extrusion. Using PLA/SCGs formulations was demonstrated through 3D printed complex parts with nonplanar slicing techniques, including a large-scale furniture product, validating large-format pellet extrusion 3D printers for scaling up the use of biomass-filled polymers.
@journalarticle{paramatti2024PLACoffee,title={PLA Feedstock Filled with Spent Coffee Grounds for New Product Applications with Large-Format Material Extrusion Additive Manufacturing},author={Paramatti, Martina and Romani, Alessia and Pugliese, Gianluca and Levi, Marinella},journal={ACS Omega},volume={9},pages={6423--6431},numpages={9},year={2024},publisher={American Chemical Society},doi={10.1021/acsomega.3c05669},url={https://pubs.acs.org/doi/10.1021/acsomega.3c05669},keywords={3D printing, Biopolymers, Extrusion, Organic polymers, Plastics}}
2023
Recycled polycarbonate and polycarbonate/acrylonitrile butadiene styrene feedstocks for circular economy product applications with fused granular fabrication-based additive manufacturing
Distributed recycling and additive manufacturing (DRAM) holds enormous promise for enabling a circular economy. Most DRAM studies have focused on single thermoplastic waste stream. This study takes three paths forward from the previous literature. 1) expanding DRAM into high-performance polycarbonate/ acrylonitrile butadiene styrene (PC/ABS) blends, 2) extending PC/ABS blend research into both recycled materials and into direct fused granular fabrication (FGF) 3-D printing and 3) demonstrating the potential of using recycled PC/ABS feedstocks for new applications in circular economy contexts. A commercial open source large-format FGF 3-D printer was modified and used to assess the different printability and accuracy of recycled PC and PC/ABS. The mechanical properties (tensile and impact) following the ASTM D638 and D6110–18 standards were quantified. A weather simulation test (ASTM D5071–06) was performed to assess outdoor performance. Finally, two applications in sporting goods and furniture were demonstrated. In general, better printability was achieved with recycled PC/ABS compared to recycled PC, as well as good dimensional accuracy at printing speeds of 30 and 40 mm/s. Minimal qualitative differences and discoloration were visible on the samples after accelerated weather exposure, with results in accordance with the state-of-the-art. The rPC/ABS results from tensile tests show similar values to those of rPC for elastic modulus (2.1 ± 0.1 GPa), tensile strength (41.6 ± 6.3 MPA), and elongation at break (2.8 ± 0.9%), which are also comparable with previous studied virgin 3-D printed filaments. Similarly, impact energy (115.78 ± 24.40 kJ/m2) and resistance values (810.36 ± 165.77 J/m) are comparable in the two tested formulations, reaching similar results compared to FFF 3-D printed filaments, as well as virgin materials for injection molding. Finally, the two demonstration products in the sporting goods and furniture sectors were successfully fabricated with rPC/ABS, achieving complex patterns and good printing speeds for recycled feedstocks. It is concluded rPC/ABS blends represent a potential high-performance feedstock for DRAM, validating its use in direct FGF 3-D printing systems and potential applications for a circular economy.
@journalarticle{romani2023rPC/ABS,title={Recycled polycarbonate and polycarbonate/acrylonitrile butadiene styrene feedstocks for circular economy product applications with fused granular fabrication-based additive manufacturing},author={Romani, Alessia and Levi, Marinella and Pearce, Joshua M.},journal={Sustainable Materials and Technologies},volume={38},pages={e00730},numpages={14},year={2023},publisher={Elsevier},doi={10.1016/j.susmat.2023.e00730},url={https://www.sciencedirect.com/science/article/pii/S2214993723001653?via%3Dihub},keywords={3-D printing, Recycling, Fused Filament Fabrication (FFF), Fused Granular Fabrication (FGF), Distributed recycling for additive manufacturing (DRAM), Mechanical properties}}
Speculative tinkering on circular design materials through 3D printing
Despite the spread of new circular materials and digital technologies, designers’ awareness of how to practically implement them is not fully achieved yet. Therefore, new ways to foster digital craftsmanship skills and experiential knowledge should be implemented. This contribution aims to reflect on digital technologies, especially 3D printing, in speculative design approaches with circular materials through the development of the materials library from the FiberEUse research project. This “materials and product library system” is an adaptive experiential tool that goes beyond merely collecting physical materials samples. It also includes possible products, speculative applications, and non-textual content, merging physical and virtual learning experiences. Its physical section comprises a materials library with flat samples of the materials and a product library with applications or cutoffs of some meaningful details of products. By analyzing the library’s development path, three incremental phases emerge in terms of interaction with circular materials and 3D printing for speculative approaches: experiencing materials, technology, and products. The first phase aims to preliminary explore the potential and qualities of materials through traditional craftsmanship skills. The second phase deal with the first experimentations with the technology, understanding the limits and influence on the expressive-sensorial qualities. The third phase is oriented toward new applications, investigating the possible outcomes from a formal point of view. As a synthesis, the tinkering process emphasizes the active role of experiential tools in spreading the use of circular materials and digital technologies, helping acquire new skills through an experiential approach. It also adds a further level to the exploitation of materials libraries, paving the way for new possible uses, i.e., distributed replication, participation, and implementation. As a result, materials libraries assume a more active role in the experiential knowledge transfer even during their development, representing a practical path to building new skills. Hence, a new model of materials libraries may emerge as a replicative learning and speculative design tool.
@conferencepaper{romani2023Antwerp,title={Speculative tinkering on circular design materials through 3D printing},author={Romani, Alessia and Rognoli, Valentina and Levi, Marinella},booktitle={Connectivity and Creativity in times of Conflict. Cumulus Conference Proceedings Antwerp 2023},editor={Vaes, Kristof and Verlinden, Jouke},pages={317--321},numpages={5},year={2023},isbn={978-94-0149-676XX},publisher={Academia Press.},doi={10.26530/9789401496476-063},url={https://library.oapen.org/handle/20.500.12657/85856},keywords={Circular economy, Materials library, Additive Manufacturing, Materials experience, Experiential learning}}
Materials Libraries. designing the experiential knowledge transfer through prototyping
Experiential knowledge plays a crucial role in exploiting new materials within real contexts, i.e., designing products and applications. As a result, understanding and transferring this kind of knowledge has gained increasing attention, as well as developing new experiential tools addressing this challenge. This contribution investigates the role of physical prototypes in designing new experiential tools for the knowledge transfer of emerging materials and technologies, i.e., Materials Libraries. The analysis is performed through a reflective practice approach based on two practical case studies dealing with new materials from waste for 3D printing. The former Materials Library focuses on the recycling of composite materials from products at their End-of-Life in industrial contexts, i.e., wind turbine blades. The latter one, RepMat Library, is an ongoing experimentation that aims to develop an open source Materials Library to collect new 3D printable materials and applications from waste-based polymers and biomass involving distributed networks and local communities, i.e., makerspaces and fablabs. After briefly explaining the two case studies, this work defines an outline proposal of the main contributions of prototypes in designing new Materials Libraries, which means: (i) generating and detecting the experiential knowledge to transfer; (ii) categorizing and defining the taxonomy of the tool; (iii) testing the experiential knowledge transfer; and (iv) speculating on new possible ways of using Materials Libraries. In short, prototypes were mainly used as a physical learning medium to preliminary tinker with materials and technology, as well as a validating tool for the interaction between the users and the library. Furthermore, prototypes may contribute to envisioning new ways of developing and using Materials Libraries to spread experiential knowledge, i.e., democratizing the design process of the tool by encouraging distributed, accessible, and collaborative work within local communities and distributed networks.
@conferencepaper{romani2023Eksig,title={Materials Libraries. designing the experiential knowledge transfer through prototyping},author={Romani, Alessia and Rognoli, Valentina and Levi, Marinella},editor={Ferraris, Silvia and Rognoli, Valentina and Nimkulrat, Nithikul},pages={398--411},numpages={14},year={2023},isbn={978-94-0149-676XX},publisher={Cumulus. The Global Association of Art and Design Education and Research.},keywords={Materials Experience, Material Tinkering, Research through Design, Material Driven Design, 3D printing}}
Fostering circular materials within the design practice. Materials and product library system
New models of production and consumption should be investigated in the short and mid-term since the current resources’ exploitation is overcoming the possibilities of our planet. Sustainable development and circular economy are assuming a crucial role, and several strategies for their implementation have been emerging in the last years. The individual contribution of new design strategies, circular materials, and digital technologies for exploiting circular economy practices is well-established. However, some issues still prevent the real implementation of those strategies. Designers are not fully aware of how to exploit them for real applications, although materials scientists and professionals are increasingly focused on the characterization of recycled and bio-based materials. This work aims to spread the use of circular materials amongst design practitioners by fostering the tacit knowledge of these materials through new experiential tools. This first design experimentation has been part of FiberEUse, a research project on exploiting new circular materials from recycled glass and carbon fibers. Starting from the concept of a “materials library,” a new experiential tool has been designed to stimulate the exploitation of circular materials and reach a wider network thanks to a physical and virtual learning experience. A first demo of the “materials and product library system” was exhibited at Milan Design Week 2021, and the virtual part is visible at https://fibereuselibrary.com/. This adaptive system is not only meant to collect materials samples since it also includes new products/applications and non-textual contents. Moreover, it can be used during the whole design process, facilitating the tacit knowledge transfer by direct experiencing physical and virtual contents, i.e., flat samples, product parts, pictures, and technical data. Materials and product library systems represent a potential way for design practitioners to discover new circular materials and speculate on possible applications for their exploitation within real contexts.
title = {Fostering circular materials within the design practice. Materials and product library system},author = {Romani, Alessia and Rognoli, Valentina and Levi, Marinella},booktitle = {Design for Adaptation Cumulus Conference Proceedings Detroit 2022},editor = {Lazet, Amy},pages = {862--863},numpages = {2},year = {2023},issn = {2490-046X},isbn = {978-94-0149-676XX},publisher = {Cumulus. The Global Association of Art and Design Education and Research.},}
Hangprinter for large scale additive manufacturing using fused particle fabrication with recycled plastic and continuous feeding
Ravneet S. Rattan, Nathan Nauta, Alessia Romani, and
1 more author
The life cycle of plastic is a key source of carbon emissions. Yet, global plastics production has quadrupled in 40 years and only 9 % has been recycled. If these trends continue, carbon emissions from plastic wastes would reach 15 % of global carbon budgets by 2050. An approach to reducing plastic waste is to use distributed recycling for additive manufacturing (DRAM) where virgin plastic products are replaced by locally manufactured recycled plastic products that have no transportation-related carbon emissions. Unfortunately, the design of most 3-D printers forces an increase in the machine cost to expand for recycling plastic at scale. Recently, a fused granular fabrication (FGF)/fused particle fabrication (FPF) large-scale printer was demonstrated with a GigabotX extruder based on the open source cable driven Hangprinter concept. To further improve that system, here a lower-cost recyclebot direct waste plastic extruder is demonstrated and the full designs, assembly and operation are detailed. The <$1,700 machine’s accuracy and printing performance are quantified, and the printed parts mechanical strength is within the range of other systems. Along with support from the Hangprinter and DUET3 communities, open hardware developers have a rich ecosystem to modify in order to print directly from waste plastic for DRAM.
@journalarticle{rattan2023HardwareX,title={Hangprinter for large scale additive manufacturing using fused particle fabrication with recycled plastic and continuous feeding},author={Rattan, Ravneet S. and Nauta, Nathan and Romani, Alessia and Pearce, Joshua M.},journal={HardwareX},volume={13},pages={e00401},numpages={131},year={2023},publisher={Elsevier},doi={10.1016/j.ohx.2023.e00401},url={https://www.sciencedirect.com/science/article/pii/S2468067223000081?via%3Dihub},keywords={Open hardware, 3D printing, FGF printing, Hangprinter, Recyclebot, Pellet extrusion, Waste plastic, Recycling, Open source hardware}}
Biomass waste materials through extrusion-based additive manufacturing. A systematic literature review
Circular economy and bioeconomy models have increasingly spread the principles of sustainable development through different strategies such as reuse and recycling. Biomass waste and by-products are often considered valuable resources. Digital technologies, i.e., extrusion-based additive manufacturing, may potentially foster their exploitation as new materials, although the current framework has not been clearly defined yet. This work wants to systematically review the publications focused on new materials from biomass waste or by-products for extrusion-based additive manufacturing processes. The current situation was analyzed on 69 selected works from 2016 searched on Scopus and WoS, focusing on the different raw materials, new 3D printable materials, 3D printing processes, and potential applications. Afterward, the emerging trends were highlighted through selected best practices from the design practice and industrial sectors. Despite the significant development of thermoplastic reinforced materials, i.e., PLA-filled composites, a wide range of biomass waste and by-products have been studied, especially for small format low-cost Fused Filament Fabrication. Although the academic field may be less focused on exploiting these new circular materials, the interest in new applications is increasing within the design practice and industrial sectors, fostering new synergies within bioeconomy and circular economy contexts.
@journalarticle{romani2023Review,title={Biomass waste materials through extrusion-based additive manufacturing. A systematic literature review},author={Romani, Alessia and Suriano, Raffaella and Levi, Marinella},journal={Journal of Cleaner Production},volume={386},pages={135779},numpages={19},year={2023},publisher={Elsevier},doi={10.1016/j.jclepro.2022.135779},url={https://www.sciencedirect.com/science/article/abs/pii/S0959652622053537},keywords={Additive manufacturing, Design for sustainability, Circular economy, Upcycling, Fused deposition modeling, Direct ink writing}}
2022
Material Library System for Circular Economy. Tangible-Intangible Interaction for Recycled Composite Materials
Alessia Romani, Fabio Prestini, Raffaella Suriano, and
1 more author
Currently the development of new circular materials has brought up the necessity to transfer their knowledge amongst the interested stakeholders for their real exploitation. This chapter aims to illustrate the design of a physical and virtual library system of the FiberEUse project. In particular, this library system wants to foster the development of new applications and value chains through the showcase of the new recycled composite materials and archetypal remanufactured products developed during the project. After the definition of the system concept, specific taxonomies were designed for the physical and virtual parts considering the technical properties and the expressive-sensorial qualities of the new recycled materials and products. A hierarchical organization was then designed to allow both tangible and intangible interactions with the samples, resulting in a coherent experience to explore these new recycled materials. Meanwhile, the physical exhibitors and the library website were developed to collect the physical and virtual samples. At the end, the whole system will be freely accessible through the library website and by booking a visit to the physical part. Thanks to its transdisciplinary nature, this system can stimulate the real exploitation of new value chains and applications.
@chapter{romani2022Library,series={Digital Innovations in Architecture, Engineering and Construction},isbn={978-3-031-22352-5},title={Material Library System for Circular Economy. Tangible-Intangible Interaction for Recycled Composite Materials},author={Romani, Alessia and Prestini, Fabio and Suriano, Raffaella and Levi, Marinella},booktitle={Systemic Circular Economy Solutions for Fiber Reinforced Composites},editor={Colledani, Marcello and Turri, Stefano},pages={363--384},numpages={21},year={2022},publisher={Springer International Publishing},doi={10.1007/978-3-031-22352-5_18},url={https://link.springer.com/chapter/10.1007/978-3-031-22352-5_18},keywords={Carbon fiber reinforced polymers, Circular economy, Design for sustainability, Glass fiber reinforced polymers, Material driven design, Material library, Materials experience}}
2021
Design, Materials, and Extrusion-Based Additive Manufacturing in Circular Economy Contexts. From Waste to New Products
The transition toward circular economy models has been progressively promoted in the last few years. Different disciplines and strategies may significantly support this change. Although the specific contribution derived from design, material science, and additive manufacturing is well-established, their interdisciplinary relationship in circular economy contexts is relatively unexplored. This paper aims to review the main case studies related to new circular economy models for waste valorization through extrusion-based additive manufacturing, circular materials, and new design strategies. The general patterns were investigated through a comprehensive analysis of 74 case studies from academic research and design practice in the last six-year period (2015–2021), focusing on the application fields, the 3D printing technologies, and the materials. Further considerations and future trends were then included by looking at the relevant funded projects and case studies of 2021. A broader number of applications, circular materials, and technologies were explored by the academic context, concerning the practice-based scenario linked to more consolidated fields. Thanks to the development of new strategies and experiential tools, academic research and practice can be linked to foster new opportunities to implement circular economy models.
@journalarticle{romani2021Review,title={Design, Materials, and Extrusion-Based Additive Manufacturing in Circular Economy Contexts. From Waste to New Products},author={Romani, Alessia and Rognoli, Valentina and Levi, Marinella},journal={Sustainability},volume={13},pages={7269},numpages={23},year={2021},publisher={MDPI},doi={10.3390/su13137269},url={https://www.mdpi.com/2071-1050/13/13/7269},keywords={product design; additive manufacturing, circular materials, material recycling, recycling and reuse, design for sustainability, 3D printing}}