A promising method of enhancing the circular economy is distributed plastic recycling. In this study plastic waste is upcycled into 3-D printing filament with a recyclebot, which is an open source waste plastic extruder. The recyclebot is combined with an open source self-replicating rapid prototyper (RepRap) 3-D printer, to enable post-consumer ABS plastic filament from computer waste to be further upcycled into valuable consumer products pre-designed in the digital commons. The total electrical energy consumption for the combined process is monitored and an economic evaluation is completed. The coupled distributed recycling and manufacturing method for complex products reduces embodied energy by half, while reducing the cost of consumer products to pennies. This economic benefit provides an incentive for consumers to both home recycle and home manufacture, which tightens the loop on the circular economy by eliminating waste associated from transportation and retail. It is clear from the results that waste plastic can be significantly upcycled at the individual level using this commons-based approach. This tightening of the loop of the circular economy benefits the environment and sustainability as well as the economic stability of consumers/prosumers.

The rapid technical evolution of additive manufacturing (AM) enables a new path to a circular economy using distributed recycling and production. This concept of Distributed Recycling via Additive Manufacturing (DRAM) is related to the use of recycled materials by means of mechanical recycling process in the 3D printing process chain. This paper aims to examine the current advances on thermoplastic recycling processes via additive manufacturing technologies. After proposing a closed recycling global chain for DRAM, a systematic literature review including 92 papers from 2009 to 2019 was performed using the scopus, web of science and springer databases. This work examines main topics from six stages (recovery, preparation, compounding, feedstock, printing, quality) of the proposed DRAM chain. The results suggested that few works have been done for the recovery and preparation stages, while a great progress has already been done for the other stages in order to validate the technical feasibility, environmental impact, and economic viability. Potential research paths in the pre-treatment of recycled material at local level and printing chain phases were identified in order to connect the development of DRAM with the circular economy ambition at micro, meso and macro level. The development of each stage proposed using the open source approach is a relevant path to scale DRAM to reach the full technical potential as a centerpiece of the circular economy.

Past work has shown that particle material extrusion (fused particle fabrication (FPF)/fused granular fabrication (FGF)) has the potential for increasing the use of recycled polymers in 3D printing. This study extends this potential to high-performance (high-mechanical-strength and heat-resistant) polymers using polycarbonate (PC). Recycled PC regrind of approximately 25 mm 2 was 3D printed with an open-source Gigabot X and analyzed. A temperature and nozzle velocity matrix was used to find useful printing parameters, and a print test was used to maximize the output for a two-temperature stage extruder for PC. ASTM type 4 tensile test geometries as well as ASTM-approved compression tests were used to determine the mechanical properties of PC and were compared with filament printing and the bulk virgin material. The results showed the tensile strength of parts manufactured from the recycled PC particles (64.9 MPa) were comparable to that of the commercial filament printed on desktop (62.2 MPa) and large-format (66.3 MPa) 3D printers. Three case study applications were investigated: (i) using PC as a rapid molding technology for lower melting point thermoplastics, (ii) printed parts for high temperature applications, and (iii) printed parts for high-strength applications. The results show that recycled PC particle-based 3D printing can produce high-strength and heat-resistant products at low costs.

Fab labs, which offer small-scale distributed digital fabrication, are forming a Green Fab Lab Network, which embraces concepts of an open source symbiotic economy and circular economy patterns. With the use of industrial 3D printers capable of fused particle fabrication/ fused granular fabrication (FPF/FGF) printing directly from waste plastic streams, green fab labs could act as defacto recycling centers for converting waste plastics into valuable products for their communities. Clear financial drivers for this process have not been studied in the past. Thus, in this study the Gigabot X, an open source industrial 3D printer, which has been shown to be amenable to a wide array of recyclables for FPF/FGF 3D printing, is used to evaluate this economic potential. An economic life cycle analysis of the technology is completed comprised of three cases studies using FPF for large sporting equipment products. Sensitivities are run on the electricity costs for operation, materials costs from various feed stocks and the capacity factors of the 3D printers. The results showed that FPF/FGF 3D printing is capable of energy efficient production of a wide range of large high-value sporting goods products. In all cases, a substantial economic savings was observed when comparing the materials and energy related costs to commercial goods (even for customized goods). Using locally-sourced shredded plastic represented not only the best environmental option, but also the most economic. For the case study products analyzed even the lowest capacity factor (starting only one print per week) represented a profit when comparing to high-end value products. For some products the profit potential and return on investment was substantial (e.g. over 1000%) for high capacity use of a Gigabot X. The results clearly show that open source industrial FPF/FGF 3D printers have significant economic potential when used as a distributed recycling/manufacturing system using recyclable feed stocks in the green fab lab context.

In order to accelerate deployment of distributed recycling by providing low-cost feed stocks of granulated post-consumer waste plastic, this study analyzes an open source waste plastic granulator system. It is designed, built, and tested for its ability to convert post-consumer waste, 3D printed products and waste into polymer feedstock for recyclebots of fused particle/granule printers. The technical specifications of the device are quantified in terms of power consumption (380 to 404 W for PET and PLA, respectively) and particle size distribution. The open source device can be fabricated for less than $2000 USD in materials. The experimentally measured power use is only a minor contribution to the overall embodied energy of distributed recycling of waste plastic. The resultant plastic particle size distributions were found to be appropriate for use in both recyclebots and direct material extrusion 3D printers. Simple retrofits are shown to reduce sound levels during operation by 4dB-5dB for the vacuum. These results indicate that the open source waste plastic granulator is an appropriate technology for community, library, maker space, fab lab, or small business-based distributed recycling.

In the Upper Peninsula of Michigan, over 500 million tons of copper rich rock were removed from mines and treated in chemical baths to extract copper. Toxic substances have been seeping into the watersheds from the resultant waste stamp sands. Recent work on developing a circular economy using recycled plastic for distributed manufacturing technologies has proven promising, and this study investigates the potential to use this approach to form stamp sand and acrylonitrile styrene acrylate (ASA) composites. Specifically, this study found the maximum amount of stamp sand that was able to be added to waste ASA by mass with a single auger recyclebot system for compounding was below 40%. The mechanical properties of the composite were evaluated up to 40%, and the addition of stamp sand reduced the material's ultimate tensile strength by about half compared to the strength of raw recycled ASA, regardless of the percent stamp sand in the composite. However, this strength reduction plateaus and the tensile strength of the ASA and stamp sand composites can be compared favorably with acrylonitrile butadiene styrene (ABS) at any level. This makes waste ASA-stamp sand composites potential replacements for outdoor applications of ABS as well as some current ASA applications. These results are promising and call for future work to evaluate the technical, economic and environmental potential for waste ASA-stamp sand composites.

Although distributed additive manufacturing can provide high returns on investment, the current markup on commercial filament over base polymers limits deployment. These cost barriers can be surmounted by eliminating the entire process of fusing filament by three-dimensional (3-D) printing products directly from polymer granules. Fused granular fabrication (FGF) (or fused particle fabrication (FPF)) is being held back in part by the accessibility of low-cost pelletizers and choppers. An open-source 3-D printable invention disclosed here allows for precisely controlled pelletizing of both single thermopolymers as well as composites for 3-D printing. The system is designed, built, and tested for its ability to provide high-tolerance thermopolymer pellets with a number of sizes capable of being used in an FGF printer. In addition, the chopping pelletizer is tested for its ability to chop multi-materials simultaneously for color mixing and composite fabrication as well as precise fractional measuring back to filament. The US$185 open-source 3-D printable pelletizer chopper system was successfully fabricated and has a 0.5 kg/h throughput with one motor, and 1.0 kg/h throughput with two motors using only 0.24 kWh/kg during the chopping process. Pellets were successfully printed directly via FGF as well as indirectly after being converted into high-tolerance filament in a recyclebot.

Following the rapid rise of distributed additive manufacturing with 3-D printing has come the technical development of filament extruders and recyclebots, which can turn both virgin polymer pellets and post-consumer shredded plastic into 3-D filament. Similar to the solutions proposed for other forms of ethical manufacturing, it is possible to consider a form of ethical 3-D printer filament distribution being developed. There is a market opportunity for producing this ethical 3-D printer filament, which is addressed in this paper by developing an “ethical product standard” for 3-D filament based upon a combination of existing fair-trade standards and technical and life cycle analysis of recycled filament production and 3-D printing manufacturing. These standards apply to businesses that can enable the economic development of waste pickers and include i) minimum pricing, ii) fair trade premium, iii) labor standards, iv) environmental and technical standards, v) health and safety standards, and vi) social standards including those that cover discrimination, harassment, freedom of association, collective bargaining and discipline.

Fused particle fabrication (FPF) (or fused granular fabrication (FGF)) has potential for increasing recycled polymers in 3-D printing. Here, the open source Gigabot X is used to develop a new method to optimize FPF/FGF for recycled materials. Virgin polylactic acid (PLA) pellets and prints were analyzed and were then compared to four recycled polymers including the two most popular printing materials (PLA) and acrylonitrile butadiene styrene (ABS)) as well as the two most common waste plastics (polyethylene terephthalate (PET) and polypropylene (PP)). The size characteristics of the various materials were quantified using digital image processing. Then, power and nozzle velocity matrices were used to optimize the print speed, and a print test was used to maximize the output for a two-temperature stage extruder for a given polymer feedstock. ASTM type 4 tensile tests were used to determine the mechanical properties of each plastic when they were printed with a particle drive extruder system and were compared with filament printing. The results showed that the Gigabot X can print materials 6.5× to 13× faster than conventional printers depending on the material, with no significant reduction in the mechanical properties. It was concluded that the Gigabot X and similar FPF/FGF printers can utilize a wide range of recycled polymer materials with minimal post processing.