Around half of the carbonate emissions from cement production are reabsorbed by the material when used in buildings and infrastructure, according to the latest IPCC climate report.

The “cement carbonation sink” absorbs an estimated 200 million tonnes of carbon every year, according to an overlooked section of the report published earlier this month ahead of the Cop26 climate conference.

“Direct CO2 emissions from carbonates in cement production are around four per cent of total fossil CO2 emissions,” says the full version of the Sixth Assessment Report from the Intergovernmental Panel on Climate Change.

“The uptake of CO2 in cement infrastructure (carbonation) offsets about one half of the carbonate emissions from current cement production.”

However, carbonate emissions only represent between 40 and 60 per cent of total emissions from cement production so carbonation will reabsorb around a quarter of the emitted carbon.

Concrete carbonation recognised for the first time

“The key chapter in [the IPCC report] recognised concrete carbonation for the first time,” said Richard Leese, director of industrial policy, energy and climate change at the Mineral Products Association, which represents the UK’s cement industry.

“Now the international accounting needs to be updated to take account of the carbonation of concrete just so they can get the math right.”

The IPCC report sets out the latest scientific understanding of climate change, which for the first time states that increases in atmospheric greenhouse gases are “unequivocally caused by human activities”.

“Global warming of 1.5 degrees Celsius and two degrees Celsius will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades,” it states.

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