Driving on asphalt containing 99% renewable material

Downer EDI and the City of Boroondara in Victoria have partnered together to produce asphalt containing 99% renewable materials. This is well over double Australian best practice levels of 30-40% renewables, with some limited facilities achieving higher production levels.

The 99% renewable asphalt utilises waste items such as toner from printer cartridges and used tyres that would typically be stockpiled or sent to landfill. According to Downer’s executive general manager road services, Dante Cremasco, “Improved recycled material availability and process improvements for large-scale production means that we can work with progressive and environmentally conscious suppliers and customers to achieve world’s best practice.”

Downer consulted extensively with recycling companies such as Close the Loop to tailor the product offering to suit a road construction application. The team also worked closely with Ammann, a supplier of mixing plants, to design its Bayswater High Recycling Technology (HRT) asphalt mixing plant to allow high levels of diverse recycled materials to be incorporated.

10,000 tonnes of 99% recycled asphalt, a typical annual volume used by a Victorian council, could include:

• 24.7 km of re-used asphalt
• 7.5 million recycled glass bottles
• 1250 used car tyres saved from landfills
• 425,000 recycled printing cartridges

These components contribute to lower CO₂-e emissions, with up to 350 tonnes of CO₂-e emissions avoided compared to non-recycled asphalt and 52% fewer CO₂-e emissions compared to conventional asphalt. The gross energy use to produce the 99% recycled asphalt is 22.6% lower than that of conventional asphalt.

Additionally, the recycled materials and innovative product mix and design increase the fatigue life of the asphalt, improving durability and resistance to fatigue cracking. Other achievements include a 30% improvement in deformation resistance, increasing product ability to resist damage from heavy traffic; and a 16% improvement in stiffness that improves bearing capacity to carry heavy traffic, providing the ability to lay a thinner surface and even further lowering CO₂-e emissions.

All recycled materials were Melbourne metropolitan sourced, not only saving transportation costs but also delivering an avenue to recycle local landfill and stockpile waste into a useful product. The product had an overall lower cost than conventional asphalt, thanks to the availability and source of the recycled materials.