Recycling your old milk jugs into 3D printer filament can save as much as 99 cents on the dollar and a little bit of the environment at the same time, according to a study by researchers at Michigan Tech University.
It also uses far less energy than conventional means of recycling the plastic, according to the report by Dr. Joshua Pearce entitled, "Life-Cycle Analysis of Distributed Recycling of Post-consumer High Density Polyethylene for 3-D Printing Filament."
"Filament is retailing for between $36 and $50 a kilogram, and you can produce your own filament for 10 cents a kilogram if you use recycled plastic," Pearce, an associate professor of materials science and engineering/electrical and computer engineering, said. "There's a clear incentive, even if you factor in the cost of buying the RecycleBot."
Pearce's team did a life-cycle analysis on an average milk jug made from HDPE plastic. After cleaning it and cutting it in pieces, they ran it through an office shredder and a RecycleBot, which turns waste plastic into 3D printer filament.
The energy savings is only about 3 percent in urban areas, where the plastic has to travel less during the collection and recycling process.
"Where it really shows substantial savings is in smaller towns like Houghton (where Michigan Tech. is located), where you have to transport the plastic to be collected, then again to be recycled, and a third time to be made into products," Pearce said. The energy savings is as much as 80 percent in small towns and rural areas.
In that same light, recycling your own milk jugs uses 90 percent less energy than making virgin plastic from petroleum.
Pearce acknowledges that HDPE plastic isn't ideal though.
"It shrinks slightly as it cools, so you have to take that into account, but if you are making something like a statue or a pencil holder, it doesn't matter," he said.