Next time you knock back a bottle of beer you might just be contributing to the new road surface on your local state highway.

The thorny question of what to do with waste glass could be solved thanks to an innovative solution by Tauranga engineers that involves using crushed glass to replace conventional sand in roading asphalt.

Glass recycling is the hot topic on everyone's lips in the Bay of Plenty after Waste Management stopped collecting glass from kerbside recycling collections in Tauranga and the Western Bay of Plenty in March.

The move means most residents either have to take their glass to one of the eight recycling stations in the region, or deposit it in their general waste going to landfill.

Even if every resident in New Zealand sent all their glass to recycling, it is estimated that 27 per cent of that, or roughly 60,000 tonnes of glass will still make its way to landfill each year due to a lack of large scale uses for the recycled material.

Downer and Road Science engineers believe they have found a way to solve this problem by using glass sand asphalt for roading.

Developed through collaboration between engineers and laboratory technicians, the product directly replaces conventional sand with crushed glass sand to produce a mix that will handle the same as a standard asphalt mix, but actually provide better performance on the road.

'A key reason why this project was conceived was because currently we use sand sourced mainly from beaches and rivers in asphalt mixes,” says Tauranga engineer Nik Vishwanath.

'By crushing recycled glass into sand and incorporating it into our products we are not only reducing the amount of glass waste going to landfill, but also ensuring our beaches and rivers are preserved for future generations.”

Nik is a professional process engineer and a member of the Tauranga branch of Engineering New Zealand. He has been working with Road Science since graduating from the University of Auckland in 2016 with a degree in chemical and materials engineering and has managed the development of this material.

The innovative product is currently being trialled on a 1500sqm site at the intersection of Horsham Downs and Lake Road in the Waikato after Waikato District Alliance was approached with the idea.

"We're always looking at ways to innovate and improve environmental sustainability where possible," says Waikato District Alliance capital works manager Steve Uffindell.

"This single project has used the previously non-recyclable material created by almost 12,000 bottles and has produced an asphalt that has, so far, outperformed the existing material."

Downer is now evaluating whether it can use crushed glass as its primary source of sand and whether there are other waste streams that could be incorporated into roading materials in the future.