Events of recent years have obviously seen thousands of tons of used surgical masks dumped every month without a real vision of how to manage them. Although the world appears to have passed through this period, a serious industrial eco-solution must be developed to deal with the waste.
Researchers are investigating the possibilities of plasma gasification as an eco-friendly technique to convert surgical mask waste into clean energy products.
A recent project in this area was conducted by Kaunas University of Technology (KTU), Lithuania and the Lithuanian Energy Institute.
After conducting a series of experiments, they obtained synthetic gas (aka syngas) with a high abundance of hydrogen.
Gasification allows huge amounts of waste to be converted to syngas, which is composed of several gases including hydrogen, carbon dioxide, carbon monoxide, and methane. “During our experiments, we played with the composition of this synthetic gas and increased its concentration of hydrogen, and, in turn, its heating value,” said Samy Yousef, a chief researcher.
For the conversion of surgical masks, the researchers applied plasma gasification on defective FFP2 face masks, which were shredded beforehand into a uniform particle size, and then converted to granules that could be easily controlled during treatment.
The highest yield of hydrogen was obtained at a steam-to-carbon ratio (S/C) of 1.45. Overall, the obtained syngas showed a 42% higher heating value than that produced from biomass, said the group.
Existing infrastructure can handle it
Yousef’s team researches recycling and waste management, and are always looking for waste that is present in huge amounts and that possesses a unique structure. They have conducted pyrolysis experiments on cigarette butts, used-wind turbine blades, and textile waste. All have shown promising results for upscaling and commercialization. This latest exploration, of the recycling of surgical masks, used a different method.
“Gasification is a traditional waste management technique,” he said. Unlike pyrolysis, he explained, “which is still a new and developing method, we don’t need much investment in developing infrastructure.”
The use of arc plasma gasification, which they have applied to the decomposition of surgical masks, uses high temperatures, and with this approach “we can decompose face masks to gas within a few seconds”.
“In pyrolysis, it takes up to an hour to get the final product. In advanced gasification, the process is almost instantaneous.”
He said advanced gasification techniques, such as plasma gasification, are more efficient in obtaining a better concentration of hydrogen (up to 50%) during synthetic gas production. Moreover, plasma gasification decreases the amount of tar in the syngas, which improves its quality.
Hydrogen-rich gas is better for heating
According to Yousef, plasma gasification is one of the best methods to obtain synthetic gas that is rich in hydrogen.
Different types of hydrogen are classified according to the manner of production: ‘grey’ is obtained from natural gas or methane, ‘green’ from renewables (the power being used to electrolyse water), and ‘blue’ from steam reforming.
“Maybe we could call ours ‘black’ hydrogen, as it’s made from waste?” he said half-jokingly.
The yield of syngas was around 95% of the total amount of feedstock. The remaining products were soot and tar. The main compounds in the collected tar appeared to be benzene, toluene, naphthalene and acenaphthylene. According to the researchers, it can be used as a clean fuel in different industries with low carbon emissions.
The soot was produced in the last stage of plasma gasification. Its main component is black carbon, which can be used for things like energy production, wastewater treatment, and agriculture, or as a filler material in composites.
The researchers believe the method has the potential to be commercialized. Although hydrogen can be separated from the obtained syngas, it can also be used alongside a mixture of gases – as such, it already has a higher heating value than gas produced from biomass.
