Case Study – Mutu circular platform active across Dempsey Wood
Background
Dempsey Wood (an ISC member since 2017) is one of New Zealand's leading civil contractors, with more than 500 staff working across infrastructure, earthworks and land development projects nationwide. Alongside its technical delivery, Dempsey Wood has built a strong sustainability focus, actively looking for ways to reduce waste and improve how resources are used across its multi-site operations.
Like many civil contractors, Dempsey Wood's biggest inefficiency wasn't a lack of materials, it was visibility. Surplus pipes, kerbing blocks, manhole steps, tactile pavers and other components would often sit unused on one site while another site placed a fresh order for the same item, with no easy way for teams to see what was already available across the business.
Dempsey Wood partnered with Mutu, an ISC ISupplier and member whose platform lets site teams within an organisation list and claim surplus resources, giving a business real-time visibility of everything available across its projects. The goal was straightforward: keep valuable materials in use, cut unnecessary procurement, divert more resources away from landfill and capture the data behind that impact.
Implementation and results
Dempsey Wood rolled Mutu out across its site teams, who began listing surplus stock and claiming materials from other sites in place of new orders. In under a year, the platform was being used to actively redistribute materials at scale:
- 300+ material exchanges completed between Dempsey Wood sites
- More than 1,500 tonnes of embodied carbon and 500 tonnes of waste emissions avoided
- $373,410 in procurement costs avoided through material reuse rather than new purchases
- 638 tonnes of material diverted from landfill
- $191,265 saved in disposal costs
- 5,000+ individual construction components reused, including pipes, kerbing blocks, manhole steps and tactile pavers
Momentum continued to build the longer the platform was in use. December 2025 was a record-breaking month for Dempsey Wood, with more than $60,000 in procurement savings recorded, the largest monthly total recorded by any business on the Mutu platform to date.
Impact delivered
- Carbon Emissions: More than 100 tonnes of carbon emissions redirected from landfill and over 1,500 tonnes of embodied carbon emissions avoided but reusing materials that already existed within the business resulting in not needing to procure new.
- Financial: $370,000+ in direct procurement savings and $191,000 in avoided disposal costs.
- Environmental: 638 tonnes of material kept out of landfill and back in productive use across projects, supporting circular economy outcomes and reducing embodied impacts associated with new material extraction and manufacture.
- Operational: Reduced reliance on internal "does anyone have spare X" broadcast emails between site teams, freeing site staff to focus on delivery rather than informal resource-hunting.
- Commercial: Trackable, exportable sustainability metrics that Dempsey Wood uses as evidence of sustainable procurement practice in tenders and client reporting. This real-time data directly supports credits such as Sustainable Procurement Strategy and Resource Recovery and Management under the IS Rating Scheme.
Dempsey Wood's Sustainability, Environmental and Quality Manager, Mike Dunphy, said the results changed how the business thinks about surplus material:
"We knew we needed a better way to manage surplus materials, but we never expected results like this. The savings have been phenomenal. Not just in costs but in reducing waste and improving efficiency across all our projects. Mutu has completely transformed how we approach resource management."
Site-level feedback has been just as positive, with teams reporting the platform is simple to use in the field.
"Mutu is great at bridging the communication divide between site teams and, as an unintended consequence, has reduced the frequency of internal spam-type emails which frees up our people to concentrate on building."
Community impact
Not every piece of surplus material has a home within Dempsey Wood's own sites and rather than let that material go to landfill, Mutu also connects businesses with community partners who can use it.This opportunity on Mutu led to Dempsey Wood's second contribution to the Hawke's Bay recovery following Cyclone Gabrielle.
Through Mutu, Dempsey Wood donated 29 surplus concrete pipes and risers (more than 20 tonnes of material valued at over $16,000) left over from a project. The pipes were picked up and transported to Hawke's Bay with support from the Porangahau Catchment Group, which coordinated funding for transport, while Dempsey Wood's team helped load and prepare the materials for the journey.
The donation was distributed to local farmers to rebuild culverts, drainage systems and stream crossings damaged in the floods, infrastructure essential to restoring farm access and flood resilience in the region.
Lessons learned
- Visibility, not volume, was the core problem with most of the surplus material already existing within the business, they simply weren’t visible across projects.
- Adoption compounds: the biggest savings months came 6 months after go-live, once listing and claiming materials became routine practice on site.
- Sustainability data with a clear dollar value travels further internally. Procurement and commercial teams engaged with the results as readily as environmental teams did.
Looking ahead
Dempsey Wood plans to expand Mutu's use across more of its project portfolio, use the platform's data to refine procurement strategy and set new internal sustainability benchmarks, and begin working with suppliers and subcontractors to extend circular economy practices further into its supply chain.
As Mike Dunphy puts it:
"Mutu has fundamentally changed the way we think about materials and waste in construction. What was once considered surplus is now seen as an opportunity to save money, reduce environmental impact, and build smarter."