Page 54 - 2022 Sustainability Report

ENVIRONMENTAL STEWARDSHIP

Our Cement Business

Cement and aggregates are critical components of building materials, such as concrete, and in the construction and
maintenance of roads, buildings, bridges and other infrastructure assets that are vital to economic growth and quality of life.
While it is well known that the cement sector is a significant contributor to global GHG emissions, a holistic approach that
takes into account the environmental impacts of embodied carbon during the entire life cycle of cement and concrete
building materials (including materials sourcing, distribution, use, productive reuse, recycling and disposal) means that
cement and concrete products can play an important role in a sustainable low-carbon economy.

Recarbonation

Emerging research suggests that a large percentage of the CO originally emitted during cement production can be
2
captured over the lifecycle of concrete through the process of “recarbonation”. According to Cembureau, the European
Cement Association, recarbonation is a slow process that occurs in concrete where lime (calcium hydroxide) in the cement
reacts with carbon dioxide from the air and forms calcium carbonate. At the end of their useful life, buildings and
infrastructure (reinforced concrete structures) are demolished. If the concrete is then crushed, its exposed surface area
increases and this further increases the recarbonation rate. The amount of recarbonation is even greater if stockpiles of

crushed concrete are left exposed to the air prior to reuse. 1
In fact, according to a 2021 report of the Intergovernmental Panel on Climate Change (IPCC), around half of the
carbonate emissions from cement production are reabsorbed by the material when used in buildings and infrastructure.
The “cement carbonation sink” absorbs an estimated 200 million tonnes of carbon every year, according to an
overlooked section of the report published ahead of the COP26 climate conference.

“Direct CO emissions from carbonates in cement production are around four per cent of total fossil CO emissions,” says
2
2
the full version of the Sixth Assessment Report from the Intergovernmental Panel on Climate Change. “The uptake of CO 2
in cement infrastructure (carbonation) offsets about one half of the carbonate emissions from current cement
production.” 2

1 https://lowcarboneconomy.cembureau.eu/5-parallel-routes/downstream/recarbonation/
2 IPCC Report — “Climate Change 2021, the Physical Science Basis”, pg. 688

52 2022 SUSTAINABILITY REPORT