From Butts to Blacktop

Cigarette butts are the latest waste product to be recycled into asphalt pavements

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Soon, the asphalt we drive on could be paved with cigarette butts instead of littered with them. That’s at least the hope of researchers at RMIT University in Melbourne, Australia.

And that’s good because cigarette butts are a bigger environmental problem than you might realize. Nearly 6 trillion cigarettes are produced every year, creating 1.2 million tons of garbage.

What’s worse is that these figures are expected to increase by more than 50% by 2025, mainly due to an increase in world population. And due to the chemicals and heavy metals in the filters, that garbage is technically toxic waste.

But there’s hope. Last year, a team at RMIT University led by Dr Abbas Mohajerani found that using cigarette butts in the production of clay-fired bricks trapped the pollutants inside, preventing things like arsenic, cadmium, chromium and nickel from leaching into the environment.

"This research shows that if just 2.5 percent of the world's annual brick production incorporated 1 percent cigarette butts, we could completely offset annual worldwide cigarette production," Mohajerani says.

The research team also concluded that bricks made with cigarette butts can actually have superior properties than those without. According to the team, the energy used to fire bricks is reduced by more than half when butts are added, and the final product makes for better insulation.

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Recently, the team moved on from bricks to blacktop, demonstrating that asphalt mixed with cigarette butts can handle heavy traffic and also reduce thermal conductivity.

This means the product could not only solve a huge waste problem but also up the sustainability factor of asphalt pavements.

Mohajerani, a senior lecturer in RMIT’s School of Engineering, said he was keen to find solutions to mounting cigarette butt waste.

“I have been trying for many years to find sustainable and practical methods for solving the problem of cigarette butt pollution,” Mohajerani says. “In this research, we encapsulated the cigarette butts with bitumen and paraffin wax to lock in the chemicals and prevent any leaching from the asphalt concrete. The encapsulated cigarettes butts were mixed with hot asphalt mix for making samples.

“Encapsulated cigarette butts developed in this research will be a new construction material which can be used in different applications and lightweight composite products. This research shows that you can create a new construction material while ridding the environment of a huge waste problem.”

The idea behind encapsulation involves restricting the interaction of cigarette butts with fluids which prevents chemical translocation. 

The research showed that by testing samples of the butt-enhanced asphalt, not only could the material handle heavy traffic, it also tended to trap less heat from the sun. Asphalt that holds heat for a shorter time is said to help reduce the urban heat island effect.

The project, a result of five years of research, has been published in full in the journal Construction and Building Materials.

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