Waste cooking oil turned into 3D printing resin

Waste cooking oil from a McDonald’s restaurant has been converted via a one-step process into high-resolution 3D printing resin.

Waste cooking oil
The plastic butterfly printed from the researchers’ cooking oil-derived resin showed features down to 100 micrometres and was structurally and thermally stable (photo by Don Campbell)

The advance by researchers at the University of Toronto Scarborough makes it more economical to produce 3D printing resin, and the plastics made from it are biodegrade. The work is described in ACS Sustainable Chemistry & Engineering.

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“The reasons plastics are a problem is because nature hasn’t evolved to handle human-made chemicals,” said Andre Simpson, a professor at U of T Scarborough’s department of physical and environmental sciences who developed the resin in his lab. “Because we’re using what is essentially a natural product – in this case fats from cooking oil – nature can deal with it much better.”

Simpson found that the molecules used in commercial resins were similar to fats found in cooking oils, leading him to ask if a viable resin could be created using waste cooking oil.

In their research, the team acrylated the waste cooking oil in a one-step lab process, using about one litre of used cooking oil to make 420 millilitres of resin. The addition of a photoinitiator readied the product for use on a commercial 3D printer.

The resin was then used to print a plastic butterfly that showed features down to 100 micrometres and was structurally and thermally stable.

“We found that McDonald’s waste cooking oil has excellent potential as a 3D printing resin,” said Simpson, an environmental chemist and director of the Environmental NMR Centre at U of T Scarborough.

According to Simpson, commercial uses for waste cooking oil exist, but creating a high value commodity could remove some of the financial barriers with recycling waste cooking oil since many restaurants have to pay to dispose it.

Furthermore, conventional high-resolution resins can cost upwards of $525 per litre because they’re derived from fossil fuels and require several steps to produce. All but one of the chemicals used to make the resin in Simpson’s lab can be recycled, meaning it could be made for as low as $300 per tonne, which is cheaper than most plastics.

Another key advantage is biodegradability. The researchers found that burying a 3D-printed object made with their resin in soil lost 20 per cent of its weight in about two weeks.

“If you bury it in soil, microbes will start to break it down because essentially it’s just fat,” Simpson said in a statement.