Cement manufacturing plants are among the activities that contribute the most to warming. Cement manufacturing is responsible for 8% of CO2 emissions into the atmosphere, followed by energy production and transportation, according to the International Energy Agency (IEA). However, this is one of the industrial sectors where decarbonization is most difficult. Meanwhile, in this context, the first initiatives are emerging for the implementation of technologies aimed at capturing this CO2 so that it stops being thrown into the atmosphere. It seems like science fiction, but it may be less and less so.

The decarbonization effort (elimination of these CO2 emissions) must be enormous in the cement sector in the coming years. Climate protection policies and the sector’s own commitments place as a horizon the ambitious goal of achieving a zero emissions balance by mid-century.

The high CO2 emissions in these factories occur in two main focuses of their production process. On the one hand, conventionally, cement manufacturing uses fossil fuels to manufacture clinker (the base material to obtain cement), which entails high emissions of CO2 and other gases.

And, on the other hand, emissions inherent to the production process occur when limestone (calcium carbonate) must be decomposed to extract CO2 and produce clinker.

The emissions in this part of the process account for 60% of the total that cement companies throw into the air (the rest comes from combustion).

One of the serious drawbacks of the cement manufacturing process is that the gases from combustion come into contact with the limestone and release CO2. And, furthermore, another negative factor is that the oven releases many other highly polluting gases (nitrogen oxides, volatile compounds, tire residue, sulfur, carbon monoxide, dioxins and furans…), which are mixed, and very They can hardly be separated from CO2.

Thus, both the emissions from decarbonation and fuel combustion go together, which greatly complicates the removal or separation of CO2.

To respond to the problem, one of the formulas that are making progress are technologies to capture and neutralize CO2, in order to prevent it from being thrown into the atmosphere.

And one of those in contention is the one promoted by the company Leilac, which has designed a technology for the calcination phase with capture of CO2 emissions as a pure and recoverable flow.

In this procedure, calciner tubes transmit radiant heat to the limestone without putting it in contact with the combustion gases, but rather keeping them separated.

The result is that “the decarbonation process (the extraction of CO2 from limestone) is carried out in a clean environment, so that the CO2 is extracted, in a pure way and can even be handled later,” explains Luisa Serrano, chemical engineer. and processes at Leilac, which promotes these technologies to be used in cement plants.

In a subsequent process, this CO2 can be captured, stored, used in industry and or buried underground (a task in which Leilac does not intervene directly)

“Faced with other types of technological proposals that capture CO2 in the post-production phase, we propose a preventive solution for the industry to move from an energy-intensive calcination process to the use of clean alternative fuels, with an easy-to-use calcination oven. fit into existing normal plants,” says Serrano.

Another advantage of this calciner is that it works so that it can use alternative fuel, such as electricity from renewable sources (wind, solar…). “This way, we avoid having to use more fossil energy in the event that (after completing the entire process) CO2 has to be separated from the other gases,” adds this specialist.

Its promoters point out that Leilac’s technology can be incorporated into a cement plant with minimal loss of activity time, since it can be coupled taking advantage of the time when they make their regular stops. “Modular design allows for flexible integration and adaptation options”

Meanwhile, to complete the global solution to the CO2 problem, cement companies must continue working to achieve the use of other fuel sources (biomass, hydrogen…) to reduce gas emissions at the exit of their kilns. “We aspire to be able to introduce electrification and low-carbon alternative fuels throughout the process,” say Leilac spokespersons.

One of the factors that can “motivate” cement companies to reduce their CO2 emissions is the expected progressive increase in the cost of CO2 emission rights, subject to the purchase and sale market for these quotas.

This is a trend resulting from climate action policies. Cement plants must acquire declining emission rights at auction (they are awarded by the European Commission with increasingly restrictive criteria, to activate decarbonization); and the forecast is that its costs may rise to 150 and 200 euros per ton. “If you have to add this cost of emissions to the cost of producing clinker, your processes may be unviable if emissions reduction is not addressed,” Serrano warns.

“Leilac expects its cost of CO2 capture to be significantly lower than the cost of emitting CO2 under the EU emissions trading system, making it an economically attractive option for the industry,” company officials say.

“Each plant has unique characteristics, although the objective is always the same: capture CO2. The great challenge we have is what to do with these sources with many components, how you handle them, how you separate them, how you compress them…” adds Serrano.

For the Leilac engineer, another of the great advantages of this solution is that it acts preventively, so that if the cement company decides to install systems to separate the gases at the exit of the kiln, the investment is less because action has already been taken in the decarbonation phase.

Faced with a scenario of new increases in the price of emissions, the cement sector has initiated a process to reduce emissions, which includes the use of alternative fuels to fossils, such as waste and biomass to generate thermal energy for the kiln, as well as low carbon clinkers or the use of cements with less clinker content (and use of active additions).

However, it is estimated that they will have to reduce their emissions by 1.4 billion tons of CO2 per year, which suggests that solutions based on carbon capture can play an important role in the future.

At this point it will also be essential to check how policies to promote carbon storage evolve.

In the United States, the Inflation Reduction Act included incentives for this task, such as a subsidy of $85 per ton to capture and permanently store CO2 of industrial origin.x

Meanwhile, CO2 emissions in cement factories in Catalonia decreased by 12% last year, which was due to a decrease in cement consumption and the progressive substitution of fossil fuel (petroleum coke) for other alternative energy sources ( sewage sludge, plant biomass, wood, fuels derived from industrial waste and meat flour). The result is that in Catalonia 45% of the fuel used is no longer fossil, according to Salvador Fernández, president of Ciment Català, which brings together companies in the sector. In Catalonia, 70% of emissions come from the decarbonation of limestone and the rest from combustion.

Cement consumption was reduced by 9% in 2022 in Catalonia, where exports have also decreased to the point that plants operate at 60% of their potential.

The sector complains above all about the competition that cement production entails in other countries (China or Turkey) where environmental costs are not assumed. For cement companies, the emissions trading system governs, which means that in a few years all plants will have to buy emission rights through auctions.

In relation to the emergence of technologies to capture CO2 in cement companies, Salvador Fernández maintains that “there are several techniques, they are not yet fully mature” but “they are beginning to see experiences” that will condition the sector.

Given the boost that the EU wants to give to these technologies, the president of Ciment Català demands that the central government establish specific support programs to promote their progressive implementation. “The sector’s goal is to achieve a balance of zero net emissions in 2050, and in the period 2030-2050, most of the CO2 reductions will come from direct CO2 captures,” he tells this newspaper.

Leo Bejarano, director of the Catalan Office of Canvi Climàtic, explains that “the sector is working a lot” in the field of technology for capturing and using CO2. “They are researching and innovating a lot, they are getting their act together, there are prototypes, but there are still no larger-scale initiatives; We need to make the leap,” he explains to this newspaper.

“It is a technology that interests us to eliminate emissions from processes and there is no way to replace them by changing energy sources,” he adds. Bejarano maintains that in these cases “we should go to a system of capture and use of CO2”, although “that does not mean storage”, but reuse of this gas for other uses and processes.