Why has the cement industry become the main battlefield of carbon reduction in China?

During the two sessions this year, Hu Shuguang, a member of the National Committee of the CPPCC and professor of Wuhan University of Technology, pointed out that the carbon emission reduction of the cement industry is directly related to the success or failure of the national "double carbon" strategy, therefore, the country will inevitably develop and introduce high standard carbon emission reduction technical requirements for cement production, and the building materials industry should actively respond.

In fact, for the cement industry to reduce carbon, the policy level has been very important. On December 21, 2021, the Ministry of Industry and Information Technology, the Ministry of Science and Technology and the Ministry of Natural Resources jointly issued the "14th Five-Year Plan" for the Development of Raw Material Industry.

According to the plan, the raw material industry is a typical "high energy consumption, high material consumption, high pollution" industry, which is the key control object of national energy conservation and emission reduction. Therefore, the green development of the raw material industry is an important part of the plan. The plan emphasizes the comprehensive implementation of energy-saving and low-carbon actions around the target node of reaching the peak of carbon and carbon neutrality.

The plan gives three numerical indicators: During the "14th Five-Year Plan" period, "the comprehensive energy consumption per ton of steel in the steel industry will be reduced by 2%, the energy consumption per unit of clinker of cement products will be reduced by 3.7%, and the carbon emissions of electrolytic aluminum will be reduced by 5%."

How can cement, alongside steel and electrolytic aluminum, become the main battlefield for carbon reduction?

If the cement industry were a country, it would rank third on the carbon emissions list, behind China and the United States. The world produces 3.5 billion tons of ordinary Portland cement each year, and each ton of cement produced emits 561-622 kilograms of carbon dioxide, and the cement industry as a whole contributes about 8% of global carbon dioxide emissions.

The world's cement looks to China. In 2020, China's cement production is about 2.4 billion tons, accounting for about 60% of the world's total, and China's cement industry's carbon emissions account for about 14% of the country's total carbon emissions. Therefore, the low-carbon transformation of the traditional cement industry is of great significance for China and the world.

1.The carbon emission of the industry is only second to that of China and the United States, and clinker production accounts for 90% of it

The above mentioned total carbon emissions from the cement industry cover the full life cycle of cement.

Cement production begins with the mining and treatment of limestone (mainly calcium carbonate), which is then mixed with clay (mainly silicate) and fed to a rotary kiln at 1450 ° C to 1500 ° C for calcination. This process emits a lot of carbon dioxide, and the bulk material left behind is mainly composed of calcium silicate, or clinker. The clinker is cooled, gypsum and auxiliary cementing materials are added, and ground into a powder, which is cement.

In the entire cement production process, the clinker production stage emits the most carbon dioxide, accounting for about 95% of the total production process, more than half of which comes from limestone calcination, and less than half from the fuel used in this process

2. Fuel carbon reduction program: from waste heat utilization to green fuel

In 2019, Lafarge announced that half of the rotary kiln fuel at a cement plant in Nigeria is biomass, mostly from agricultural waste, and the company is also working to mine more fuel from municipal solid waste.

In fact, the practice of adding solid waste such as tires, organic waste, sewage sludge and plastics to cement kilns has been around since the 1970s.

In the beginning, these practices were more about reducing costs for companies, since garbage was certainly cheaper than coal, and some local governments even paid cement companies as a way to dispose of municipal waste.

In recent years, the cement industry has actively promoted the corporate strategy of solid waste as a fuel, more calling it a social responsibility to solve plastic waste and mitigate climate change, such as the Mexico-based Cemex Group.

From the perspective of fossil energy combustion and utilization, the utilization efficiency of heat energy has improved in recent years. Producing 1 ton of clinker required 3.75 gigajou in 2000 and 3.5 gigajou in 2014, reducing energy consumption by an average of 0.5% per year. Since then, according to the International Energy Agency, the energy intensity of clinker production has stagnated at 3.4-3.5 gigajou per ton. Based on such energy consumption, the production of 10 tons of clinker is roughly equivalent to the heat energy consumed by a small household in a heating season.

The rate of decline in energy consumption is a little slow, but there are still ways to reduce carbon and increase efficiency.