RMIT researchers say sequestering cigarette butts into bricks could not just help solve a global littering problem, but cut brick production costs.
The research project at RMIT University, led by Dr Abbas Mohajerani, was an attempt to address the issue of environmental damage caused by millions of tonnes of toxic waste being dumped into the environment in the form of cigarette butts.
Cigarette butts have poor biodegradability, and it can take many years for them to break down. During this process, heavy metals such as arsenic, chromium, nickel and cadmium, which have been trapped in the filters, leach into the soil and waterways.
"About 6 trillion cigarettes are produced every year, leading to 1.2 million tonnes of cigarette butt waste. These figures are expected to increase by more than 50 percent by 2025, mainly due to an increase in world population," Dr Mohajerani pointed out.
“In Australia alone, people smoke about 25 to 30 billion filtered cigarettes a year and, of these, about 7 billion are littered."
According to his research, if just 2.5 percent of the world's annual brick production incorporated 1 percent cigarette butt content, it would be possible to completely offset annual worldwide cigarette production.
Adding butts to the mix allowed the researchers to cut the energy needed to fire bricks by up to 58 percent.
The added material also resulted in lighter bricks, with better insulation properties, reducing household heating and cooling costs, while maintaining properties very similar to those of normal bricks.
When the bricks are fired, the heavy metals and other pollutants in the cigarette butts are trapped and immobilised in the bricks, reducing the problems caused by leaching and contamination.
As the amount of cigarette butt content increased in the bricks, they became cheaper. The researchers tested bricks with up to 10 percent cigarette butt content. At that level, the dry density of the bricks decreased by up to 30 percent, and the compressive strength decreased by 88 percent.
While greater cigarette butt content reduced the suitability of the resulting bricks for load-bearing purposes, the researchers stated that it is possible to adjust these levels depending on the intended purposes of the bricks.