Ellen Phiddian
Cosmos science journalist
Is it better that a disposable face mask ends up in the ocean or the atmosphere? An international team of researchers have figured out how to convert face masks into oil fuel, and they say that this is a less environmentally damaging way to dispose of them.
Face masks are mostly made of a substance called polypropylene, which we know can be turned into oil with a process called pyrolysis. Pyrolysis involves heating things in an oxygen-free environment – instead of combusting entirely into gases, the carbon-rich materials become a combination of liquid oil, char (a solid carbon-based material) and some gasses (called syngas).
Pyrolysis with polypropylene is a well-established process. But disposable face masks have a number of other materials in them that have, until now, made pyrolysis more difficult.
The team of researchers, who are based at universities in China, Singapore, and South Korea, found that there was an optimum combination of conditions for the main three layers of mask – ear straps and metal wires still had to be removed. When heated to between 456° and 466°C, the face mask components mostly turned into a carbon-rich and energy-dense oil, which could then be combusted for electricity.
Since combustion involves releasing CO2, this is still ultimately a polluting process. But the researchers think it might be the least destructive way to deal with the face masks on the basis of a life-cycle analysis.
The team predicted CO2 emissions, and the leakage of a list of other dangerous compounds, that would make it into the environment from their pyrolysis process as well as “conventional waste management approaches” (incineration or landfill).
According to these numbers, the oil conversion is overall a better outcome than either municipally burning the masks, or sending them to landfill.
“We verified that upcycling post-consumer surgical masks into value-added energy products represents a sustainable and promising route with notable environmental benefits,” says Dr Xiangzhou Yuan, a researcher at Korea University in Seoul, and co-author on a paper describing the research, published in Bioresource Technology.