This study explores the potential to reach a circular economy for post-consumer Recycled Polyethylene Terephthalate (rPET) packaging and bottles by using it as a Distributed Recycling for Additive Manufacturing (DRAM) feedstock. Specifically, for the first time, rPET water bottle flake is processed using only an open source toolchain with Fused Particle Fabrication (FPF) or Fused Granular Fabrication (FGF) processing rather than first converting it to filament. In this study, first the impact of granulation, sifting, and heating (and their sequential combination) is quantified on the shape and size distribution of the rPET flakes. Then 3D printing tests were performed on the rPET flake with two different feed systems: an external feeder and feed tube augmented with a motorized auger screw, and an extruder-mounted hopper that enables direct 3D printing. Two Gigabot X machines were used, each with the different feed systems, and one without and the latter with extended part cooling. 3D print settings were optimized based on thermal characterization, and both systems were shown to 3D print rPET directly from shredded water bottles. Mechanical testing showed the importance of isolating rPET from moisture and that geometry was important for uniform extrusion. The mechanical strength of 3D-printed parts with FPF and inconsistent flow is lower than optimized fused filament, but adequate for a wide range of applications. Future work is needed to improve consistency and enable water bottles to be used as a widespread DRAM feedstock.
Another possible solution - reusable containers 
Cruz, F., Lanza, S., Boudaoud, H., Hoppe, S., & Camargo, M. Polymer Recycling and Additive Manufacturing in an Open Source context: Optimization of processes and methods. 
Investigating Material Degradation through the Recycling of PLA in Additively Manufactured Parts 
Mohammed, M.I., Das, A., Gomez-Kervin, E., Wilson, D. and Gibson, I., EcoPrinting: Investigating the use of 100% recycled Acrylonitrile Butadiene Styrene (ABS) for Additive Manufacturing. 
Kariz, M., Sernek, M., Obućina, M. and Kuzman, M.K., 2017. Effect of wood content in FDM filament on properties of 3D printed parts. Materials Today Communications. 
Kaynak, B., Spoerk, M., Shirole, A., Ziegler, W. and Sapkota, J., 2018. Polypropylene/Cellulose Composites for Material Extrusion Additive Manufacturing. Macromolecular Materials and Engineering, p.1800037. 
O. Martikka et al., "Mechanical Properties of 3D-Printed Wood-Plastic Composites", Key Engineering Materials, Vol. 777, pp. 499-507, 2018 
Yang, T.C., 2018. Effect of Extrusion Temperature on the Physico-Mechanical Properties of Unidirectional Wood Fiber-Reinforced Polylactic Acid Composite (WFRPC) Components Using Fused Deposition Modeling. Polymers, 10(9), p.976.