Low carbon cement

July 12, 2023 | Neil Kolwey, SWEEP Industrial Program Director & Building Electrification Specialist

This week the planet broke the record for the hottest average global temperature ever recorded, underscoring the urgent need to accelerate our greenhouse gas (GHG) emission reduction efforts. To achieve our climate goals, we need to decarbonize all the important sectors of our economy, including the industrial sector. Cement production is one of the largest emitting industrial sectors, and it accounts for about six percent of the world’s total GHG emissions. In the six states where SWEEP works (Arizona, Colorado, Nevada, New Mexico, Utah, and Wyoming), there are 11 large cement facilities, and in Colorado the three cement facilities account for 16 percent of the state’s total industrial GHG emissions. 

Federal and state “Buy Clean” programs for cement and steel are becoming an important driver of innovation and decarbonization in the cement and concrete industries. As a result of the Biden administration’s Buy Clean policies for federal procurement, concrete producers who wish to bid on federal construction projects must develop environmental product declarations (EPDs) for their concrete mixes, to demonstrate that their mixes meet the federal requirements for embedded GHG emissions per ton of concrete. Similarly, in Colorado concrete producers competing on state construction projects will need to demonstrate that the carbon footprint of their mixes meets state guidelines. Basically, an EPD documents the carbon footprint of the concrete mix, including the emissions from producing the cement used in the mix. 

There are three main ways that cement producers can reduce the carbon intensity of their cement. The first is improved energy efficiency. Energy efficiency improvements are generally very cost effective and help facilities reduce their operating costs per ton of cement. Depending on the age of the plant and improvements already implemented, cement facilities can improve their energy efficiency by 5-10 percent.

The second method is through the use of supplementary cementitious materials (SCMs), which means substituting materials such as fly ash or ground limestone for some percentage of the “clinker,” the key ingredient which gives cement its binding properties. Because all of the cement facility’s purchased fuel and most of its electricity is consumed for clinker production, using a lower clinker-to-cement ratio results in lower carbon emissions per ton of cement produced. In addition, a lower clinker-to-cement ratio reduces the process carbon dioxide (CO2) emissions from calcination of limestone, which account for about 59 percent of total GHG emissions from cement production. Experts estimate that cement producers can lower their carbon intensity by up to 20 percent through using higher percentages of SCMs, without sacrificing product quality. (Concrete producers can also use SCMs in place of cement in their concrete mixes.) 

The third method for lowering the carbon intensity of cement production is through switching from coal to lower carbon fuels such as natural gas. For example, switching fuels from 100 percent coal to 100 percent natural gas would reduce GHG emissions per ton of cement by about 18 percent.

The two largest cement producers nationally, which also have facilities in the Southwest, are Holcim and Cemex. Both have cement plants in Colorado, and Holcim also has a large plant in Utah. These two companies are also leaders in efforts to decarbonize cement and concrete production. Holcim has plans to achieve aggressive GHG reduction goals for 2030, through energy efficiency, use of lower carbon fuels, and increased use of SCMs. Holcim also has developed a brand of low-carbon concrete, called ECOPact, which features an innovative mix of supplementary cementitious materials and “admixture technology.” Holcim is employing its ECOPact concrete mixes in several projects around the world. 

Cemex has set a goal to reduce its CO2 emissions per ton of cement by 47 percent by 2030. It plans to  achieve this goal through energy efficiency, use of lower carbon fuels, and the use of SCMs. Cemex also has a goal to reduce the carbon intensity of its concrete mixes by 41 percent by 2030. 

To address the lower carbon fuels strategy, the Colorado Holcim and Cemex facilities have natural gas pipeline infrastructure in place which allows the facilities the flexibility to burn higher percentages of gas (such as 50-75 percent) during periods when gas prices are relatively low. (For example, industrial gas prices were less than $5.50 per million British thermal units from around 2016-20, and are projected to be below this level again by 2025.)

The Southwest Energy Efficiency Project (SWEEP) urges all cement producers to develop aggressive GHG reduction goals and plans, and to implement the three strategies discussed above at all their facilities, including those in the Southwest. In addition to reducing carbon and other pollutant emissions, these actions will help the facilities improve their competitiveness in the market for clean construction materials. 

States can help move cement and concrete producers in this direction by adopting “Buy Clean” policies like Colorado’s, reinforcing the federal Buy Clean efforts. States should also require the large industrial GHG emitters (for example, those with annual emissions of more than 25,000 metric tons CO2 equivalent), including cement facilities, to set GHG reduction goals and publicize their five-year plans for carbon emission reductions. These goals and plans will help stakeholders and the public hold the cement producers accountable and help them be part of the solution to our climate crisis.