In an effort to drive down the production cost of biodiesel, researchers have developed an eco-friendly way of extracting triacetin, a combustion-enhancing additive, from an abundant waste source: cigarette butts. Recycling cigarette butts in this way would not only dispose of waste but put it to sustainable use.
Made from biological sources like edible and non-edible oils, animal fats and waste restaurant grease, biodiesel is a renewable, biodegradable fuel, an alternative to conventional ‘fossil’ diesel with low harmful greenhouse gas emissions. It sounds good on paper, however, the high cost of biodiesel production is the main barrier to its worldwide marketing.
An effective solution is to mix biodiesel with an additive like the triglyceride triacetin. Studies have shown that triacetin can contribute to reducing air pollution and increase biodiesel’s combustibility. The problem is that triacetin is generally produced chemically, which consumes a lot of chemicals and produces a lot of waste and toxic residue. This means that an alternative, eco-friendly source of triacetin is needed.
Researchers from Kaunus University of Technology (KTU), Lithuania, have collaborated with the Lithuanian Energy Institute to develop a way of extracting triacetin from an ample supply of waste products: cigarette butts.
“In our research group, we are working on the topics of recycling and waste management, therefore we are always looking for the waste, which is present in huge amounts and has a unique structure,” said Samy Yousef, lead and corresponding author of the study. “Cigarettes are made of three components – tobacco, paper and a filter made of cellulose acetate fibers – and are a good source of raw materials and energy. Plus, cigarette butts are easy to collect as there are many systems and companies for collecting this waste in place.”
Previous attempts have been made using pyrolysis to extract raw materials from cigarette waste, but here, the researchers adopted an original approach by not trying to separate the cigarette into its components.
“There are studies which, similarly to us, are using pyrolysis as a method, but they are applying it to filter components only,” Yousef said. “In this case, the pre-treatment of the material is needed to separate all components. Since tobacco is a toxic waste, the disposal of it requires special care, and due to the technologically complicated process to separate the components of the cigarette waste, this is not economically feasible.”
The researchers conducted a series of experiments using pyrolysis to thermally decompose cigarette butts at temperatures of 1,202, 1,292 and 1,382 °F (650, 700 and 750 °C). They could extract varying amounts of triacetin-rich oil, char and gas, depending on the temperature used. The maximum amount of triacetin compound (43%) was extracted at 1,382 °F (750 °C), with yields estimated at 38 wt% oil, 25.7 wt% char, and 36.4 wt% gas. At the same temperature, the char product had a calcium-rich, porous structure that could be used as an adsorbent.
“All the products have real applications,” Yousef said. “Char, which, in our case, is porous and very rich in calcium, can be used for fertilizers or wastewater treatment as an absorbent and energy storage. Gas can be used for energy purposes. Last but not least is oil, rich in triacetin, which can be used as an additive to biodiesel to reduce the cost.”
It's estimated that 4.5 trillion individual cigarette butts are polluting our global environment. Recycling them in the way proposed by the researchers would not only clear the waste, it would provide a sustainable use for it.
The study was published in the Journal of Analytical and Applied Pyrolysis.
Source: KTU