Life cycle analysis of distributed recycling of post-consumer high density polyethylene for 3-D printing filament

Abstract

The growth of desktop 3-D printers is driving an interest in recycled 3-D printer filament to reduce costs of distributed production. Life cycle analysis studies were performed on the recycling of high density polyethylene into filament suitable for additive layer manufacturing with 3-D printers. The conventional centralized recycling system for high population density and low population density rural locations was compared to the proposed in home, distributed recycling system. This system would involve shredding and then producing filament with an open-source plastic extruder from postconsumer plastics and then printing the extruded filament into usable, value-added parts and products with 3-D printers such as the open-source self replicating rapid prototyper, or RepRap. The embodied energy and carbon dioxide emissions were calculated for high density polyethylene recycling using SimaPro 7.2 and the database EcoInvent v2.0. The results showed that distributed recycling uses less embodied energy than the best-case scenario used for centralized recycling. For centralized recycling in a low-density population case study involving substantial embodied energy use for transportation and collection these savings for distributed recycling were found to extend to over 80%. If the distributed process is applied to the U.S. high density polyethylene currently recycled, more than 100 million MJ of energy could be conserved per annum along with the concomitant significant reductions in greenhouse gas emissions. It is concluded that with the open-source 3-D printing network expanding rapidly the potential for widespread adoption of in-home recycling of post-consumer plastic represents a novel path to a future of distributed manufacturing appropriate for both the developed and developing world with lower environmental impacts than the current system.

General Design Procedure for Free and Open-Source Hardware for Scientific Equipment

“…By reducing the amount of material used, the environmental impact is minimized as the processing and transportation embodied energy are all reduced by the reduced use of material [43][44][45][46]. This can be done by eliminating non-functional bulk to designs, and, in 3D printed designs, minimizing infill percentage to fulfill mechanical requirements.…”

“…The use of distributed digital manufacturing using widespread and accessible tools such as the RepRap 3D printer and open PCB mills [47] help to reduce both the environmental impact [43][44][45][46] as well as reduce the economic costs of production [48][49][50][51]. Lead times can also be reduced, as well as improving maintainability.…”

A low carbon footprint approach to the reconstitution of plastics into 3D-printer filament for enhanced waste reduction

“…For instance, scissors were useful in cutting down the main sides of the bottles into sheets, before feeding the resulting sheets into the paper shredder. In order to obtain granules of the HDPE, the milk cartons had to be reclaimed and processed by the shredder a minimum of five time to produce a feedstock suitable for the extruder, producing a granule size ranging from 2-5mm 3 .…”

“…The prevalence of plastics is primarily due to the wide range of advantageous material properties, such as its lightweight, durability and ability to be manufacturing using a diverse range of processes. Global plastic production is increasing rapidly and is projected to continue to increase to a level of 850 tons by the year 2050 [3]. The intensive use of plastics is now leading to several unprecedented issues relating to the disposal and recycling of this material, and is arguably now one of the biggest challenges in modern day times.…”

“…Essentially, the filament that is used in the printers are identical to the filaments produced during the extrusion phase of the classical industrial recycling process. It is therefore believed that filament generation for FDM based 3D printing may provide a viable solution to manufacturing waste recyclable plastics from used products and packaging otherwise destined for landfill, and is an emerging area of research interest by many groups worldwide [3,8,9].…”