SH1 Photo: RNZ / Dom Thomas
An American expert in low-carbon construction says New Zealand's big road building programme is a chance to find cleaner ways to build.
In the US, the government is putting $10 billion towards helping steel, concrete and other industries make products with less carbon in them.
Engineer Don Davies was in Wellington on Wednesday and said the government here could use its highway building programme as a catalyst.
"Especially in highways, especially in roadways, you pour so much concrete, it's such an opportunity for experimentation and growth and learning, in a New Zealand context, into how you could bring this forward yourself," Davies said.
Like in New Zealand, the US needed to replace a lot of old infrastructure or build from scratch.
"In the US, we're finally getting serious on the carbon conversation and there's significant investment coming into decarbonisation of these hard-to-evade industries, like steel, like concrete," he said.
Of the $10 billion for decarbonisation, a fifth or so each was being put by the Department of Energy into building cleaner steel and concrete plants.
The US's recent infrastructure Act "has super-charged money into this space in a way that I don't think many people really appreciate right now", Davies said.
Hand-in-hand with that went recent advances in measuring the carbon footprint of building materials.
The US Enviromental Protection Agency announced it was putting $180m into getting more "environmental product declarations", or EPDs, developed last week.
An EPD meant "I can tell you exactly, on demand, what the carbon footprint of that material is," Davies said.
This fuelled the creation of new, cleaner products.
For instance, the US had gone from just 800 types of concrete measured this way to 70,000 types with an EPD, he said.
He had experimented himself, renovating a building he owns in Seattle using five different new types of concrete - none of them with Portland cement in them. He said he got the strength he needed.
New Zealand's road building was an "absolute opportunity" to experiment like that, but on a mass scale, then channel what worked into the whole industry.
"The highway demand is a great place to prop up the industry ... to let that have an echo effect."
One way the US now did this was by building short stretches of highways next to existing ones, but with various different surfaces on them, then detouring the traffic on them for a while, in a real-world experiment.
As for building developers, carbon was becoming more of a clincher for them, at least as long as going low-carbon did not cost more than about 10 percent extra.
"You can't manage what you don't measure," Davies said.
"We're going to measure, we're going to track the information.
"That disclosure and transparency is coming into the system and it's changing material science, it's changing the fundamental building blocks that we've worked with, because there's winners and losers on information we normally did not track in the past which we do track now."