Cement is a big problem for the environment. Here's how to make it more sustainable

It's been said that if the cement industry were a country, it would be the world's third or fourth-largest emitter of carbon dioxide (CO2). Global cement manufacturing produced 1.6 billion metric tonnes of CO2 in 2022, the latest year for which there are figures – that's about 8% of the world's total CO2 emissions.

Reducing the amount of carbon emitted by cement production is critical to achieving global climate targets.

Cement is, of course, a key ingredient of concrete – so an obvious solution would be to reduce the amount of concrete the world needs. But concrete is the second most widely used material after water, and its global annual production is forecast to grow from 14 billion m³ today to 20 billion m³ by mid-century, as human societies urbanize and demand for infrastructure grows.

This trajectory would see CO2 emissions from the sector soar to 3.8 billion tonnes per year, based on current practice.

Unlike other sectors, where the largest share of emissions is energy-related, in cement and concrete production, more than half are process emissions, outlines a newly launched insight report from the World Economic Forum’s First Movers Coalition, in collaboration with Deloitte. The industry, therefore, requires either novel solutions to a millennia-old sector or a strong reliance on carbon capture.

Here are four main decarbonization pathways in the cement and concrete industry and the innovative solutions contributing to each of these streams:

Clinker is the primary component in cement and is extremely carbon-intensive, making up 90% of overall emissions from cement.

Replacing clinker with supplementary cementitious materials (SCMs) that are less carbon intensive directly tackles process-related emissions, but no existing commercialized solutions exist that can completely replace clinker at scale.

However, there are a number of proven ways to significantly reduce the amount of clinker needed to make cement and concrete, and one of the most promising solutions is called LC3 – Limestone Calcined Clay Cement – which can reduce CO2 emissions by around 40% compared with conventional cement.

LC3 addresses both sources of carbon emissions from making clinker. First by replacing half of the clinker with calcined clay and ground limestone, neither of which releases carbon when heated the way limestone does. Second, the clay is heated to a much lower temperature, which reduces the amount of fuel required and means electricity can be used instead of fossil fuels.

Elsewhere, scientists at the University of Cambridge have developed a “zero emissions” technique to produce cleaner clinker.

Their alternative process involves reusing cement paste (which is identical in chemical composition to limestone) from demolished buildings, with the scientists saying it could save up to three gigatonnes of CO2 a year.

The heating of limestone to produce clinker accounts for 50% of emissions in cement production.

So alternative chemistries and processes that replace limestone from the clinker-production process provide a significant way to cut emissions.

US company Brimstone has developed a process to make cement from carbon-free calcium silicate rocks - which can be found in abundance at the surface of every continent in the world - instead of limestone.

The company says its process also removes CO2 from the air because its rocks contain magnesium which can passively and permanently capture atmospheric carbon dioxide.

Sublime Systems is using calcium silicate minerals or industrial wastes to produce cement using an electrochemical process rather than heat.

Cemvision has begun piloting the production of fossil-free cement made entirely from recycled materials.

Instead of using virgin limestone and fossil fuels, the Swedish company recycles by-products from mining and steel, requiring less energy and generating no waste.

The company has designed their cement to be "drop-in", which means it can be integrated into existing buildings alongside conventional cement, to enable quick adoption.

Fuel switching and electrification are critical to lowering energy-related emissions.

Partially heating up the kiln used to make clinker with a decarbonized electricity source and replacing fossil fuels with low-carbon fuel alternatives for the remaining part can help phase out coal.

CoolBrook, SaltX and Rondo Energy have all developed electric or thermal-based alternatives to fossil-based kilns and calciners – a stage that preheats limestone before entering the kiln.

Another approach to achieve the very high temperatures required is concentrated solar, which has been tested by start-ups like Synhelion – in collaboration with Cemex – and Heliogen.

Low-carbon fuel alternatives are common to other industries as well, and go from near-term drop-in solutions, including biomass and plastic waste, to longer-term alternatives such as green hydrogen.

Point-source carbon capture, where CO2 from large sources such as power plants and industrial facilities is trapped and stored to prevent it from being released into the atmosphere, is a key method for cutting emissions in the cement and concrete industry.

Projections by the Global Cement and Concrete Association show that carbon capture, utilization, and storage (CCUS) could reduce carbon emissions by 36%, making it the largest lever to reduce the cement industry’s emissions.

The shipping town of Brevik in Norway has become the first location in the world to have a cement plant which includes carbon capture and storage (CCS) technology.

Installation of the 100-metre-tall CCS facility at the Heidelberg Materials cement plant began in August and is due to be completed by the end of 2024.

It will trap the CO2 from the clinker production process, preventing the gas from being emitted into the atmosphere, and the carbon will be securely stored underground in the North Sea.

At last year’s COP28 in Dubai, countries agreed to launch the Cement and Concrete Breakthrough initiative, which strives to make near-zero-emission cement production established and growing in every region of the world by 2030.

For this goal to become a reality, the widespread adoption of innovative cement and concrete production processes such as the four listed above will be essential.