To reduce the cost of producing biodiesel, researchers have developed an environmentally friendly method to extract triacetin, a combustion-supporting additive, from cigarette butts, a rich source of waste. Recycling cigarette butts in this way not only disposes of the waste, but also allows it to be used sustainably.
Made from biological sources such as edible and non-edible oils, animal fats and waste restaurant grease, biodiesel is a renewable, biodegradable fuel that is an alternative to traditional "fossil" diesel and has low emissions of harmful greenhouse gases. It sounds great on paper, but the high cost of biodiesel production is a major obstacle to its global rollout.
One effective solution is to blend biodiesel with additives such as triacetin. Studies show that triacetin helps reduce air pollution and improve the flammability of biodiesel. The problem is that triacetin is usually produced through chemical methods, which consume large amounts of chemicals and produce large amounts of waste and toxic residues. This means an environmentally friendly alternative source of triacetic acid is needed.
Researchers at Lithuania's Kaunus University of Technology (KTU), in collaboration with the Lithuanian Energy Research Institute, have developed a method to extract triacetin from a large amount of waste products (cigarette butts).
"In our research group, our research topics are recycling and waste management, so we are always looking for waste, which is huge in quantity and has a unique structure," said Samy Yousef, first and corresponding author of the study. "Cigarettes, which consist of three parts: tobacco, paper and a filter made of cellulose acetate fiber, are a good source of raw materials and energy. In addition, cigarette butts are easy to collect as there are many systems and companies that collect this waste."
There have been previous attempts to use pyrolysis to extract raw materials from cigarette waste, but here, the researchers took a novel approach that didn't try to separate the cigarettes into their different components.
"There are some studies similar to ours that also use pyrolysis methods, but they only apply it to filter components. In this case, the material needs to be pretreated to separate all components. Since tobacco is a toxic waste, its handling requires special care, and due to the technical complexity of the process of separating cigarette waste components, this is not economically feasible," Yousef said.
The researchers conducted a series of experiments using pyrolysis technology to thermally decompose cigarette butts at temperatures of 1202, 1292 and 1382°F (650, 700 and 750°C). Depending on the temperatures used, they can extract varying amounts of triacetin-rich oil, coke and gas. At a temperature of 1382°F (750°C), the maximum amount of triacetin compound extracted (43%) was estimated to be 38 wt% oil, 25.7 wt% coke, and 36.4 wt% gas. At the same temperature, the coke product has a calcium-rich porous structure that can be used as an adsorbent.
"All products have a practical purpose," Yousef said. "In our case, the char is porous, rich in calcium and can be used as an adsorbent and energy storage agent for fertilizers or wastewater treatment. Natural gas can be used for energy purposes. Last but not least is the oil, which is rich in triacetic acid and can be used as an additive in biodiesel to reduce costs."
An estimated 4.5 trillion cigarette butts are polluting our global environment. Recycling these cigarette butts in the way proposed by the researchers would not only remove the waste but also allow for its sustainable use.
The research was published in the Journal of Analytical and Applied Pyrolysis.