Waste cooking oil left after deep frying is a major global environmental problem. From forming products that linger in the environment to clogging up sewage lines, animal fats and vegetable oils produce virtually the same environmental effects as petroleum oils.
Researchers at U of T Scarborough, in Toronto, Canada, have now shown that it is possible to recycle it into a high-value commodity.
Using cooking oil from a local McDonalds in Scarborough, the research team, led by Professor Andre Simpson, applied straightforward one-step chemical process in the lab, using about one litre of used cooking oil to make 420ml of resin. The cost was lower compared to conventional high-resolution resins, which are derived from fossil fuel and often require several steps to make.
The resin was able to print a plastic butterfly that showed features down to 100 micrometres, and was structurally and thermally stable, meaning it wouldn’t crumble or melt above room temperature.
Moreover, the resin is biodegradable in soil. The researcher found that a 3D plastic object made with the resin lost 20 per cent of its weight in about two weeks of being buried in the soil.
Because it’s just fat, microbes actually like to eat it, said Simpson, and they do a good job at breaking it down.
“The reasons plastics are a problem is because nature hasn’t evolved to handle human-made chemicals,” he said.
“Because we’re using what is essentially a natural product, in this case, fats from cooking oil, nature can deal with it much better.”
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 of it. 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 USD per tonne, which is cheaper than most plastics. It also cures solid in sunlight, opening up the possibility of pouring it as liquid and forming the structure on a work site.
The results of the research are published in the journal ACS Sustainable Chemistry & Engineering. Simpson received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC), the Canada Foundation for Innovation (CFI), Government of Ontario, and the Krembil Foundation.