Utility trials recycled materials for sustainable infrastructure

Recycled materials are taking centre stage in a trial transforming trench backfilling with recycled glass, plastic, rubber and crushed concrete, with the innovation set to reduce landfill waste, slash emissions and leverage circular economy models. 

Greater Western Water (GWW) is taking part in an innovative pilot to see if a mix of recycled materials can be used successfully in place of crushed rock to backfill trenches on busy roads. 

Funded by Sustainability Victoria through the Recycling Victoria Research and Development Fund and in partnership with Victoria University (VU) and Ground Science, a combination of recycled materials have been used to backfill two trenches at GWW’s Sunbury depot. 

The mix of recycled materials has been lab tested by VU and will be monitored at GWW’s site over the next nine months to analyse if it is strong enough to withstand the demands of heavy truck loads over a long period. 

A report outlining the findings, recommendations and potential future use will be provided to Sustainability Victoria at the end of the trial. 

GWW General Manager of Operations and Delivery Solutions Jodie Hallam said projects like this pave the way for long-term environmental benefits by potentially turning recycled materials into viable products. What’s more, circular economy initiatives are very closely aligned with one of GWW’s key priorities – Caring for Country. 

“It's a new way to reduce landfill waste and provides a cost-effective, sustainable, and efficient method to backfill trenches so we can reopen access to traffic as soon as possible,” she said. 

“We see potential to share this technology with our peers across the water industry, expanding these benefits beyond our service region." 

VU Associate Professor Yaghoubi explained that collaboration with industry partners is key to the success of applied research, overcoming challenges in implementation and bringing the products to use in the real world. 

“We're talking potentially innovative green construction materials and techniques to build our transport network that could be stronger, economical and greener,” he said. 

“This alternative approach to traditional trench backfilling under trafficable areas  helps to conserve natural sand and gravel, which is becoming scarce, and finds useful applications for waste materials like plastic, tyres and glass, reducing the amount sent to landfill.” 

Driving down emissions 

GWW is running a 12-month field trial at its site in Sunbury and is already three months into the process, Hallam said.  

“Two trenches are filled with recycled materials, and one with the standard material – crushed rock. The goal is to test the performance characteristics of each trial blend against the traditional materials and the environmental impact over time,” she said.   

“Heavy traffic, including trucks and light commercial vehicles, will pass over these trench crossings to see if the reused materials perform as well as traditional ones.” 

All the recycled materials being used in the trial are sourced locally from Victoria. 

“Transporting these materials needs to be as low-emission as possible. That’s part of the reason we use a batching plant just 15 minutes from our depot. If we scale this, we’ll need to optimise the supply chain further to avoid increasing emissions elsewhere,” Hallam said.  

Circular opportunities 

Hallam said the water sector is naturally aligned with circularity, with water and wastewater systems already naturally following that structure. But materials reuse is an opportunity not yet fully realised.  

“With this trial, we’re asking how the sector can fully embrace a lifecycle approach, not just the closed-loop models we’re used to,” she said.  

“Circular models offer more than environmental benefits; they create economic and social value. New jobs emerge in local communities, and the use of finite resources is minimised. 

“This trial shows how we can reduce Scope 3 emissions and innovate in ways that benefit multiple sectors. The challenge is to think beyond our industry and work with partners to scale these initiatives.” 

Learning to collaborate 

Scaling the innovation is the next step, Hallam said: “but it all starts with a minimum viable product to test if it works”. 

“Scaling innovations like this requires an ecosystem shift. Partners like the batching plant need to adjust their operations to handle recycled materials. It shows that operational processes must change as industries move toward circular models,” she said.  

“An important part of this project is learning to collaborate with partners outside the water sector. We’re testing new materials, but also new ways of working. Innovation happens faster when each partner understands their role in the bigger picture.” 

Hallam said that if the trial succeeds, GWW will work with partners and the wider sector to discuss how best to scale up the innovation. 

"Scaling is the hardest part of innovation. It’s not just about GWW - it’s about the entire water community adopting these methods. We need economies of scale to make it work,” she said.  

“While we produce recycled materials like biochar from biosolids, collaboration with suppliers is essential to expand our impact. Sharing what we learn from this trial could encourage other utilities to join us."