By Jeremy Sole, Executive Officer, Sustainable Steel Council

The infrastructure sector is on the frontline of climate response – and local government is one of its most powerful actors.

From specifying materials to managing landfills and overseeing public assets, councils are uniquely placed to influence carbon outcomes across the full life cycle of building materials they procure into the built environment.

But despite progress in areas such as energy efficiency and transport emissions, a critical piece of the puzzle is still under-addressed: the embodied carbon locked into construction materials, and the long-term implications of how we assess and procure them.

There is now widespread awareness that up-front emissions – those generated in the manufacturing and delivery of building materials – are substantial. In many cases, they account for the majority of emissions associated with public infrastructure. But focusing only on embodied carbon at the point of installation tells a deceivingly incomplete story.

True climate accountability requires whole-of-life thinking: a long-range view of how materials perform, degrade, emit, and recover over decades of use, deconstruction and reuse.

Take timber – often positioned as the most sustainable option because of its carbon sequestration during growth, timber’s end-of-life profile is rarely considered with the same scrutiny. In Aotearoa New Zealand, most structural timber is treated with chromated copper arsenate, making it toxic in landfill and difficult to recover or recycle. Engineered wood products are increasingly common, but their composite glues and treatments further complicate circularity.

Meanwhile, the ‘brown’ materials of the past are becoming greener. Concrete blends using alternative cementitious materials and recycled aggregates can reduce embodied carbon by up to 70 per cent. 

Low-carbon steel is already available in the New Zealand market. And the transition of the Glenbrook Steel Mill to electric arc furnace production, scheduled for later this year, will significantly cut emissions from domestic steelmaking by using scrap and renewable energy.

Steel has another major advantage: true circularity. It can be reused, remelted or repurposed indefinitely without performance loss – a property few materials can claim. The Hinuera Sheds project in Waikato, where nearly 200 tonnes of steel from a deconstructed port facility were successfully reused structurally, is a recent example of what’s possible with foresight, good design and planning.

The problem lies not with individual materials, but with how we specify and assess them. Material selection is too often based on initial carbon profiles, without factoring in end-of-life risks, de-sequestration of CO₂, or whole-of-system carbon impact.

Overspecification is a related concern, particularly in structural steel. In public projects, it’s not uncommon to find components designed to significantly exceed load requirements – significantly increasing the steel required, and therefore the calculated embodied carbon in the project. This has serious environmental and cost implications, especially when lower-carbon alternatives are readily available but not specified due to lack of awareness or alignment.

What’s needed is a shift in public procurement frameworks, from short-term metrics to long-term outcomes. Councils and council-controlled organisations can embed whole-of-life thinking into:

• procurement policies – with requirements for whole-of-life low carbon in circular materials, reuse opportunities, and a balanced recognition of up-front and end-of-product life in carbon disclosures
• asset management plans, by factoring in long-term performance, material degradation and replacement costs
• waste strategies, reflecting the up-front waste as well as the real end-of-life impacts of materials, especially mitigation of the use of products that will eventually end up in council‑managed landfills
• climate strategies – with full-scope accounting of embodied and operational emissions across infrastructure life spans and beyond to end-of-product life.

Critically, none of this requires reinventing the wheel. Councils already have many of the tools needed to support better decision-making. What’s needed now is alignment across asset planning, sustainability targets and procurement settings.

At the Sustainable Steel Council, we do not promote one material over another. Steel, timber and concrete each have essential roles in a resilient built environment. What we call for is transparency, integrity and consistency in how material impacts are assessed.

If we value timber’s sequestration potential, we must also account for its toxicity at end of life. If we penalise steel for historical emissions, we must also recognise its recyclability and rapid decarbonisation. If we criticise concrete for its emissions intensity, we should also acknowledge its evolving circular potential – and that concrete absorbs CO₂ during recycling.

Put simply, sustainability is not a snapshot; it requires a systems lens over time.

As stewards of public land, assets, and investment, councils have both a leadership role and a long-term duty. That means asking tough but necessary questions at the start of every project, including:

• What happens to this material in 30, 50 or 100 years?
• Can it be safely reused, recycled or repurposed?
• What liabilities – environmental or financial – might we be leaving for future generations?

These are not technical afterthoughts; they are strategic and up-front procurement choices, core to climate leadership and intergenerational equity.

By embedding whole-of-life thinking into infrastructure decisions, local government can help futureproof both communities and the climate.