‘Game-changer’ greenhouse gas reducing concrete enters NZ

A new technology in concrete that could save New Zealand the amount of carbon emissions equivalent to 6.3 flights Auckland to Christchurch for every house built here on average has been brought into the country by leading manufacturer Stevenson.

It works by sequestering CO2 – sinking captured, waste carbon into its mixture and saving it from emission as a greenhouse gas.

Its arrival in New Zealand is dubbed ‘absolutely a game changer’, because the cement in concrete is responsible for 8% of the world’s CO2 emissions, a greenhouse gas implicated in climate change. Concrete is ahead of aviation fuel as a global climate culprit: aviation fuel sat at 2.5% of CO2 emissions prior to COVID-19. (Agriculture sat at 12%).

Concrete is also the most abundant man-made material in the world.

“We’re beating the Aussies in bringing this high tech to our region, although they’re on the cusp of introducing it too,” says Anthony Bitossi, general manager of Stevenson Concrete, a New Zealand-founded concrete supplier, which is currently assessing its first batches of concrete using the technology. Concrete made with with CarbonCure technology will be available to the market within the next few weeks.

“Along with a number of other carbon-decreasing initiatives we are using, this technology is going to change the way New Zealand builds houses, footpaths, roads, pipes, and thousands of other man-made, everyday objects. “Stevenson has brought it into the New Zealand mainstream, just as this technology is used in countries like Singapore, North America and parts of Europe,” he says.

First developed around 2015 by Canadian company CarbonCure, the concrete works through a dual carbon-reducing action.

“A key component of concrete is cement,” says Bitossi. “Cement has a very high CO2 impact because it’s made from the burning of limestone. This new, high-tech concrete reduces the amount of cement used by injecting CO2 gas into the manufacturing process, effectively sequestering it, and replacing the lost volume of cement with the same volume of gas.

“Even better, the CO2 is captured from emissions produced in the refining of petroleum – such as from Marsden Point. Captured this way, it’s put into pressurised tanks, and shipped to us, then added to the raw materials during the batching process, before it’s mixed in and put in trucks to a destination. It thus has a dual CO2-reducing action.

“So, it substitutes a portion of the volume of cement, and also works as a type of very effective carbon sink – something the world is looking for more and more. Carbon dioxide remains trapped in the concrete and cannot be emitted. The process has no effect on the concrete’s strength whatsoever.”

At Stevenson’s Drury quarry and concrete manufacturing plant (one of five plants in the Auckland region), the concrete is undergoing final internal quality assurance. It is widely used throughout the world now to build everything from skyscrapers to sewers. It will soon be made available to Stevenson’s New Zealand customers.

“These include large government and local government clients,” says Bitossi. “Our new concrete is also relevant to every home builder in the country. New Zealand is currently going through a building boom, with 41,000 new home consents in the pipeline. Every house contains on average 50 cubic metres of concrete. If every builder in the country were to use it on these up-coming consents we’d reduce carbon emissions equivalent to approximately 6.3 flights Auckland to Christchurch on each and every house built.

“Carbon sequestration is part of the new world of reversing emissions,” says Bitossi. “In New Zealand, we’ve seen this traditionally as planting forests. Technologies like this – which are emerging and proven in the rest of the world – provide us with another, effective answer to emissions. They are part of the way ahead.”