Amid the COVID-19 pandemic, massive quantities of discarded surgical masks were being disposed of monthly, and a comprehensive strategy for proper management was lacking. While the global community has navigated through the crucial phase successfully, there is an urgent need to formulate a robust industrial eco-solution for addressing this waste.
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Scientists from the Kaunas University of Technology (KTU) and the Lithuanian Energy Institute are actively working on developing a sustainable solution for managing surgical mask waste. Their focus is on exploring the potential of plasma gasification as an environmentally friendly energy technology to transform discarded surgical masks into clean energy products.
Following a series of experiments, they successfully generated synthetic gas, commonly known as syngas, which exhibited a significant concentration of hydrogen.
There are two ways of converting waste to energy – by transforming solid waste into liquid product, or gases. Gasification allows converting huge amounts of waste to syngas, which is similar to natural and is a composition of several gases (such as 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.
Samy Yousef, Chief Researcher, Kaunas University of Technology
To convert surgical masks, the researchers employed plasma gasification on faulty FFP2 face masks. These masks were initially shredded to achieve a consistent particle size and then transformed into granules for better control during the treatment process.
The optimum hydrogen yield was achieved at a steam-to-carbon ratio (S/C) of 1.45. In summary, the resulting syngas exhibited a 42% higher heating value compared to syngas produced from biomass.
Traditional Waste Management Technique was Improved
Yousef's research team, comprised of scientists from two Lithuanian research institutions, KTU and the Lithuanian Energy Institute, focuses on recycling and waste management, constantly seeking materials with significant volumes and distinctive structures.
Their investigations have involved pyrolysis experiments on various materials such as cigarette butts, used wind turbine blades, and textile waste, all of which demonstrated encouraging outcomes for scaling up and commercialization. However, in their latest endeavor for surgical mask recycling, they adopted a distinct method.
Gasification is a traditional waste management technique. Differently from pyrolysis, which is still a new and developing method, we don’t need much investment in developing infrastructure. Arc plasma gasification, which we have applied for the decomposition of surgical masks, means that under high temperatures generated by arc plasma, 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.
Samy Yousef, Chief Researcher, Kaunas University of Technology
According to Yousef, advanced gasification techniques like plasma gasification are more efficient in achieving a higher concentration of hydrogen, potentially reaching up to 50% in synthetic gas production. Additionally, he highlights that plasma gasification has the advantage of reducing the amount of tar present in the syngas, thereby enhancing its overall quality.
Hydrogen-Rich Gas Has Better Heating Values
Yousef asserts that, in his perspective, plasma gasification stands out as one of the most effective methods for producing synthetic gas with a high hydrogen content.
“Hydrogen increases the heating value of the synthetic gas,” details Yousef and continues the discussion on various hydrogen types: grey originates from natural gas or methane, green is derived from environmentally friendly sources (such as electrolysis), and blue is produced through steam reforming.
“Maybe we could call our black hydrogen, as it’s made from waste?” he says half-jokingly.
The syngas yield accounted for approximately 95% of the total feedstock, with the remaining by-products being soot and tar. The analysis identified benzene, toluene, naphthalene, and acenaphthylene as the primary compounds in the collected tar. Researchers suggest this tar can serve as a clean fuel in various industries, contributing to low carbon emissions.
The soot, generated in the final stage of plasma gasification, is predominantly composed of black carbon. This black carbon holds potential applications in energy, wastewater treatment, agriculture, or as a filler material in composites.
The researchers are optimistic about the commercial viability of their proposed method for recycling surgical mask waste. Yousef, a researcher from KTU, emphasizes that their primary goal was to produce synthetic gas with a high hydrogen content. While hydrogen can be extracted from the resulting syngas, it can also be utilized as a blend of gases. As a result, it already boasts a 50% higher heating value than that generated from biomass.
Journal Reference:
Yousef, S., et al. (2024). Plasma steam gasification of surgical mask waste for hydrogen-rich syngas production. International Journal of Hydrogen Energy. doi.org/10.1016/j.ijhydene.2023.09.288.