According to Sven Weidner, director of the Lägerdorf “Carbon2Business” project, the plant has already reduced emissions by sourcing electricity from windmills the company erected near its property, by replacing some of the fossil fuel used for heating the kiln with energy derived from burning biomass and nonrecyclable waste, and by bringing down the share of clinker in cement and replacing it with alternative materials. A German federal registry of emissions shows that the Lägerdorf plant has reduced about 20 percent of its CO2 emissions since 2010.

Still, the bulk of the plant’s emissions comes from the very process of turning limestone into clinker, which is all about extracting CO2 from the raw material itself. “The truth is that as long as we use chalk or limestone, there will be CO2,” Weidner says. To reduce those “unavoidable emissions,” he says, the plant’s carbon needs to be captured.

Starting in 2028, the Lägerdorf plant plans to collect up to 1.2 million tons of carbon dioxide a year, then compress and transport it by pipeline to a newly built “CO2 hub” in a chemical park on the banks of the Elbe River, in Brunsbüttel, about 20 miles away. From the hub, the gas could travel in two directions: One goes out to the North Sea by ship or pipeline, where the gas would be injected and stored, permanently, hundreds of feet below the seabed; the other direction involves reusing the gas.

The sequestration strategy is currently pursued by cement companies all over Europe and in the U.S. And while environmentalists warn about possible leaks, Susanne Buiter, chief scientist of the German Research Centre for Geosciences in Potsdam, says that “carbon capture and storage” (CCS) can be done safely in the saltwater and limestone pores at 600 to 1,200 meters below the seabed. “It will either dissolve as carbonic acid or bind with the limestone,” she says. Injection sites in the North Sea are the German government’s main solution for so-called “unavoidable emissions,” like those from the cement and other industries.