Concrete, the world’s third largest emitter of greenhouse gases

If all the concrete that is used in the world as a producing country of greenhouse effect emissions, it would be the third most polluting, behind China and the United States.

Why is it said that concrete and cement have the worst carbon balance in the industrial sector?

The cement It is the most consumed material in the world, about 150 tons per second: 14,000 million cubic meters of concrete are used each year, according to the World Cement and Concrete Association (GCCA), which groups together the main players in the sector ( the Swiss Holcim, the Mexican Cemex, or the Chinese CNBM, among others).

Construction represents 13% of world GDP.

Cement production, a key element of the concrete mix, generates about 7% of global carbon dioxide (CO2) emissions, according to the GCCA, three times more than air traffic.

“It is more than the emissions of the whole of the European Union or India, behind those of China and the United States,” Valerie Masson-Delmotte, a paleoclimatologist, co-chair of a UN group of climate experts, told AFP. Something that does not seem to be changing, with increasing urbanization in Asia and Africa.

How does cement produce CO2?

Cement, the “glue” in the granules and sand that make up concrete, is mainly made up of clinker, a product that is achieved by calcining limestone and clay in a kiln at 1,400 degrees Celsius. When burned, the limestone releases carbon dioxide.

Producing a ton of cement releases almost a ton of CO2.

This important chemical reaction, which has hardly changed since the current formula for cement was invented two hundred years ago, accounts for 70% of the industry’s emissions. The remaining 30% comes from the energy consumption of the kilns when burning the limestone.

How to decarbonize construction?

The global concrete industry, which announced its goal of achieving carbon neutrality by 2050 last year, recently explained how it would reduce its emissions by an “additional 25%” by 2030, preventing 5 billion tons from being released. of CO2 in that period.

The sector is confident that new carbon capture technologies will allow it to advance its emission reduction targets by 2050.

It is also committed to increasing the recycling and reuse of concrete. Other clues go through turning concrete into a “green” product: replacing fossil fuels from cement kilns with waste and biomass (animal meal, reused wood …).

In terms of carbon capture and storage, this industry plans to install “by 2030, 10 industrial-size structures to capture carbon.”

Large companies such as the Chinese CNBM (China National Building Material Company) promised to “play a role” in the decarbonization of the industry.

Emerging companies also want to participate in this project: the American company Solidia proposes to capture the CO2 and reinject it into the concrete. In Canada, CarbonCure is already working on the injection of liquefied CO2.

But above all, the industry is committed to the commercialization of new “green” cements that replace clinker with reused materials.

The GCCA notes that in Great Britain, the reuse rate is 26%. France adopted a new standard for low-carbon cements in May.

What is green cement? What about low-emission cement?

At the moment, these types of products are in the hands of emerging companies since traditional cement industries are lagging behind in the modernization of their production instruments, with more important investments in quarries.

One of the companies that have advanced the most is France’s Hoffmann Green Cement, which manufactures clinker-free cement based on industrial waste such as blast furnace slag, biomass fly ash or clay waste.

And although the extra costs in construction reach 25 euros (almost US $ 30) per square meter, this French company does not stop receiving orders.

“The cement industry plans to reduce its emissions in 2050 but with our proposals it can be done today”, explains the founder of Hoffmann Green Cement, Julien Blanchard.

The challenge is great: “Three out of every four infrastructures that we will see in 2050 have not yet been built,” warns the Secretary General of the United Nations, Antonio Guterres.