Industry asks government to encourage contractors to use recycled aggregates

The premium for processing aggregate with glass cullet over conventional mineral aggregate is around $2 per tonne but this extra cost isn't recognised in most tenders, according to a costs benefit analysis funded by the Glass Packaging Forum.

An amended Transit road specification introduced this year now allows for up to 5% of glass cullet to be used in the base course for roading. This will help provide a local answer for many communities that find the cost of sending glass back to Auckland for processing is often too high.

However, this isn't economically viable unless councils also include the potential cost of landfilling the glass into the equation. The introduction of sustainable construction targets could provide councils with the incentive, particularly on South Island, to use glass cullet in local roads.

With around 5% more glass packaging recovered from homes year on year, New Zealand needs to find sustainable alternative recycling uses for its glass. To finance research and development into these, industry, through the Glass Packaging Forum, has established a voluntary levy on all those making, using or selling glass containers in New Zealand.

John Webber, general manager of the Glass Packaging Forum, said that using glass in roads is common around the world but in its infancy here and unless changes are made to the procurement practices, it will be difficult to encourage uptake.

"We have assisted two local communities in Palmerston North and Nelson with funds to trial crushing glass in a mix with traditional mineral aggregate and have subsequently commissioned a report to analyse the different production process and associated costs of each. This report shows that whether glass is crushed separately and mixed later with minerals or crushed together with minerals, the costs are broadly similar," Webber said.

"The problem is that the premium for the glass cullet/aggregate blended product over a conventional mineral aggregate is around $2 per tonne. This effectively means that using 5% glass cullet in the mix may cost up to 30% more if low-cost stone is available."

Road construction projects are highly competitive and contractors will always use the lowest-cost product that complies with specification, according to Webber.

"One option could be to introduce a sustainable procurement policy along the lines of that enacted in California. The California Bill will require the California Department of Transportation to use recycled aggregates in state paving projects unless it is economically unfeasible," Webber said.