For every one ton of cement produced, there is one metric ton of carbon dioxide that is released into the atmosphere. Every year, more than 4 billion tons of cement is produced, accounting for around 8% of global CO2 emissions. If the cement industry were a country, it would be the third-largest emitter of CO2 in the world.
What to expect today:
Emissions of cement production
Reducing emissions in cement production - CarbonCure Technologies
Emissions from cement production
The direct CO2 intensity of cement production increased 1.8% per year during 2015-2020. In contrast, 3% annual declines to 2030 are necessary to get on track with the Net Zero Emissions by 2050 Scenario. Sharper focus is needed in two key areas: reducing the clinker-to-cement ratio and deploying innovative technologies.
The typical cement production process starts with limestone, which is primarily made of calcium carbonate (CaCO3). Heating the limestone at extremely high temperatures separates the calcium oxide (CaO) from CO2. This step, called calcination, is where cement’s high carbon intensity comes from. Then, the chemical reaction produces a mixture of lime known as “clinker”, which is used to make the cement, and carbon dioxide, which is emitted as waste. Cement is then mixed with water and aggregates like sand and gravel to make concrete.
Clinker is the main ingredient in cement, and the amount used is directly proportional to the CO2 emissions generated in cement manufacturing, due to both the combustion of fuels and the decomposition of limestone in the clinker production process.
From 2015 to 2020, the global clinker-to-cement ratio is estimated to have increased at an average of 1.6% per year, reaching an estimated 0.72 in 2020; this rise was the main reason for the increase in direct CO2 intensity of cement production over the period.
China is by far the world’s largest emitter of carbon dioxide being the largest manufacturer of cement. In 2020, China’s cement industry released 858.2 million metric tons of carbon dioxide (MtCO2) into the atmosphere. This was roughly seven times more than the emissions produced in India. The United States comes in fourth (after Vietnam) with total emissions totalling 40.8 million metric tons in 2020.
What about “green cement”?
Green cement is an environmentally friendly product that minimizes the carbon footprint of cement production. There are a few methods for reducing the carbon intensity of cement. One of them is utilizing fly ash in the mixture.
Fly ash is a toxic byproduct of the coal burning process that can result in severe lung disease in humans and animals through exposure. Although fly ash used to be released into the atmosphere, today the US requires fly ash be captured and stored on site at the coal-fired power plants which produce it. When mixed in with lime and water, fly ash forms a cement-like compound that reduces the carbon intensity from the chemical reaction process.
Green cement is still a nascent technology and has a long way to go down the cost curve. Deployment of green cement can help the companies down the learning curve. As the companies producing green cement scale, their costs will fall and their efficiencies will rise, and the cost premium of green cement will begin to decline.
Carbon sequestration in cement - CarbonCure Technologies
CarbonCure Technologies, founded in 2012 by Rob Niven, manufactures carbon dioxide removal technologies for concrete producers of all sizes. Based in Dartmouth, Nova Scotia, Canada, it raised a total of $12.4 million from 20 investors.
How does it work?
The technology injects a precise dosage of captured carbon dioxide into concrete during mixing, where it mineralizes. This improves the concrete’s compressive strength, enabling mix optimization and significant carbon footprint reductions as well as cost savings.
CarbonCure’s technology is retrofitted into concrete plants and lets producers inject captured carbon dioxide into fresh concrete during mixing. It then gets converted into a mineral embedded in the concrete, not only providing climate benefits but also increasing the concrete’s strength. CarbonCure injects CO₂ into fresh concrete via the Valve Box. Batching is controlled by the Control Box, which is synced with the software in the control room. CarbonCure’s tech doesn’t capture CO2 from the cement production, but instead recycles CO2 captured by nearby industrial emitters such as ethanol and fertilizer plants. Its contribution is technology that injects CO2 directly into concrete, sequestering those emissions. Adding CO2 into the mix of cement, water, sand, and other materials that make concrete creates a chemical reaction that is essentially reverse calcination—the CO2 becomes a mineral, meaning it won’t be released back into the atmosphere even if the concrete is demolished.
CarbonCure sells carbon removal credits based on this permanent CO2 storage, which help the company further develop and scale its tech, but the mineralization also makes this solution more cost-competitive with typical concrete. The mineralization itself improves the concrete strength. Just adding CO2 makes the concrete stronger. This allows the concrete producers to use less cement. Less cement means fewer CO2 emissions and lower costs for concrete producers. CarbonCure says more than two million truckloads of its mixes have been used to supply construction sites, saving more than 164,000 metric tons of carbon, and counting — the CO2 data is updated in real-time on its website. It says it has sold over 580 of its systems to concrete producers worldwide.