Cigarette butts mixed in asphalt can have surprising benefits

Europeans smoke. A lot. According to the World Health Organization, 28% of adults in Europe smoke and the continent also has some of the highest prevalence of tobacco use by adolescents. And all these millions of smokers generate gazillions of cigarette butts.

The situation is hardly better across the rest of the planet. Globally, some 6 trillion cigarette butts are discarded each year, amounting to a staggering 1.2 million tons in total. By 2025, the number might rise to 9 trillion butts with even more smokers around the planet.

Needless to say, that’s hardly a good thing and not only because sidewalks and other areas littered with cigarette butts are unsightly. Rather, cigarette filters contain heavy metals like arsenic, chromium, nickel and cadmium, which can leach into the soil and water sources. The filters are not particularly biodegradable and can take long years to break down.

Yet many of those vast amounts of butts do not necessarily have to go to waste. As often, science can come to the rescue. Cigarette butts can be repurposed as building material for homes, for instance. It also turns out that mixing them into asphalt makes road surfaces more robust and less heat-absorbent.

A team of researchers at RMIT University in Melbourne, Australia, found that asphalt fortified with cigarette butts can withstand heavy traffic and that the mixture also has reduced thermal conductivity: it absorbs less heat from the sun, thereby keeping the surface of the asphalt cooler on hot summer days.

Asphalt mixed with cigarette butts could help reduce the urban heat island effect in towns and cities in the tropics, which is a nifty benefit especially since temperatures are set to rise with the onset of global warming. “[W]e encapsulated the cigarette butts with bitumen and paraffin wax to lock in the chemicals and prevent any leaching from the asphalt concrete,” Dr Abbas Mohajerani,  senior lecturer in RMIT’s School of Engineering, explained.

“Cigarette filters are designed to trap hundreds of toxic chemicals and the only ways to control these chemicals are either by effective encapsulation for the production of new lightweight aggregates or by incorporation in fired clay bricks,” he added.

His team embedded cigarette butts securely into everyday asphalt to ensure that leftover chemicals could not leak from the butts and leach harmful toxins into the environment. “This research shows that you can create a new construction material while ridding the environment of a huge waste problem,” the Mohajerani said.