Cigarette butts create a massive and messy environmental burden. To help address the ongoing issue, engineers recently developed a method to extract something beneficial from the discarded trash. According to their findings, published in the journal Construction and Building Materials, cigarette filters can substantially strengthen recycled asphalt ahead of its reapplication onto roads.
Cigarette butts may be tiny, but they add up. The World Health Organization has estimated smokers throw away around 4.5 trillion filters every year, while recent projections indicate that number may climb as high as 9 trillion by the end of 2025. The waste also decays extremely slowly, presenting major environmental problems across not only populated areas of the world, but in forests, waterways, and oceans. Multiple organizations and advocacy groups have launched projects aimed at curbing the issue, but they face an uphill battle, especially when it comes to the larger filters.
In recent years, engineers have started infusing reclaimed asphalt pavement (RAP) with additives like cellulose fiber, similar to the material in cigarette butts. This process helps strengthen and bind the recycled asphalt for reuse on roadways. Aware of the untapped potential in cigarettes, researchers at the University of Granada in Spain and Italy’s University of Bologna decided to collaborate on a new way to wring more utility from the discarded butts.
Once they removed any residual organic material, they crushed the remaining filters (typically made with PLA plastic and cellulose fibers) and mixed them into a binding wax. Next, they pressed, heated, and cold cut their new material into two types of pellets. Pellet 1 contained only cigarette butts, while Pellet 2 featured the cigarette material and an additional recycling agent.
During the manufacturing process, the wax inside each pellet begins to melt after coming into contact with the hot, sticky petroleum substance called bitumen. Once melted, the recycled cigarette butts’ plastic fibers and cellulose integrate into the material and reinforce it by improving both its flexibility and resistance to cracking.
Researchers at the University of Granada’s Building Engineering Laboratory then evaluated three asphalt mixtures containing 40 percent reclaimed asphalt pavement and various pellet ratios against a control asphalt made without RAP.
The team determined that every cigarette filter-infused asphalt variant was more resilient than conventional asphalts. On top of this, the integration of waxes made it easier to alter the bitumen’s viscosity, which could reduce the necessary manufacturing temperature—further diminishing its energy requirements and pollution emissions.
“Overall, this study confirms the possible use of recycling agent-encapsulated fibre pellets derived from [cigarettes] in mixtures containing RAP, with the potential effects on improving fatigue resistance,” the authors concluded.
The team added that future research could focus on better optimizing how the fiber pellets are made, or increasing recycling agent amounts to enhance the asphalt’s resilience. They also believe that combining additional recycled materials with the filters may further improve the material while also making the industry even more sustainable.
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