Photo: 123RF
A new study shows using new, CO2-capturing concrete and other substances instead of traditional building materials could reduce global carbon dioxide emissions by more than 16 billion tonnes.
The study by US researchers in the journal Science found switching out concrete and other construction materials for carbon-sucking alternatives could store the equivalent of half of all human-made carbon emissions in 2021.
Some of the materials proposed were still at the exploratory stage, while others were already being used by companies.
Alternatives suggested include mixing carbon-sucking substances from the earth, such as dunite, with concrete, using wood-based materials in bricks, and swapping out asphalt bitumen for bio-oil.
Experts believe New Zealand has the right raw materials - such as dunite and wood - to switch out its building materials for replacements that store, rather than emit, CO2.
But, getting the industry to use new materials could be a challenge unless there were moves to encourage their uptake.
David Dempsey is an associate professor at the University of Canterbury's Department of Civil and Natural Resources Engineering.
He notes the largest carbon removal benefits in the study, by far, came from a new kind of concrete that includes a special CO2-capturing aggregate, such as dunite, "of which New Zealand has bountiful natural deposits in Nelson and Southland."
David Dempsey is an associate professor at the University of Canterbury's Department of Civil and Natural Resources Engineering. Photo: Supplied/ University of Canterbury
Scientists are already separately studying the potential to mine and use New Zealand's dunite to store more carbon in the soil.
Dempsey said using concrete for carbon capture would require drawing on high-purity atmospheric CO2, for which the best options in New Zealand would be sucking carbon from the flue gas coming from a biomass boiler, of which he said New Zealand had "lots".
"We'd also need to carefully check that the new concrete was just as strong and durable as existing uses," he said.
"Other removals described in the article come through clever substitution of forestry-derived materials.
"Again, New Zealand has natural advantages with our large forestry sector and the widespread use of timber in construction materials," he said.
"We'd need to think carefully about just how long the CO2 is actually stored for and what happens to it once the building is torn down.
"If the CO2 is later released from the landfill, then this kind of storage is limited," said Dempsey.
Professor Suzanne Wilkinson, of AUT University's Faculty of Design and Creative Technologies, said the building sector would be cautious and would want to see new products certified.
"The construction industry is a conservative industry and therefore requires certainty before it will invest in new materials," she said.
She said questions of cost, quality and staff training in using new materials could hold alternatives back unless there were moves to encourage their use.
Diego Elustondo of the Crown-owned wood science company Scion said the premise of the paper was promising but it appeared to favour storing carbon in masonry materials at the expense of wood-based alternatives.
He said the comparison should have considered wood-based materials which were at the same stage of development as other future materials mentioned in the paper.
"Timber, for example, has a long history of proven performance, and its benefits as a carbon sink are well documented," he said.
The planet will need countries to both rapidly cut greenhouse emissions and suck CO2 out of the air to meet nations' goals to curb planetary heating, which saw the World Meteorological Organisation declare 2015-2024 the warmest ten years on record.
Photo: 123RF
NIWA said this week that eight of New Zealand's ten warmest years have occurred since 2013, with 2024 coming in tenth.
According to the UN Environment Programme, the buildings and construction sector is by far the largest emitter of greenhouse gases globally, accounting for a staggering 37 percent of global emissions.
The World Economic Forum puts emissions from manufacturing cement alone at 8 percent of the world's total CO2 emissions and said that if cement were a country it would be the world's 3rd or 4th largest carbon emitter.
In New Zealand, the EECA puts the building and construction sector at closer to ten percent of emissions - and that includes planet-heating gases from operating buildings, including their energy use.
Currently, addressing building and construction emissions is not a major focus for this government.
The Green Building Council has estimated the government could slash the sector's impact by 20 million tonnes of emissions with building code upgrades, waste management, energy performance ratings and other measures.
Last year it sent the government a letter signed by 50 businesses and professional bodies seeking a commitment to implement the Building for Climate Change programme.
The program includes measures such as building energy efficiency ratings and changes to the Building Code to cut emissions and improve energy efficiency.
But its future has been unclear since the change in government.
The government's emissions reduction plan in December didn't include any significant measures from the programme, with just two building-related policies making it in: Expanding voluntary energy performance ratings for non-residential buildings and making it easier for people to retrofit their buildings to improve energy efficiency.
Modelling released with the plan showed government officials do not expect significant reductions to building and construction emissions as a result of the coalition's climate plans, at least over the next five years.
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