Concrete is one of the world’s most important materials. But making the cement that binds it generates about 8% of anthropogenic carbon-dioxide emissions. This is not just because of the heat involved. That could, in principle, be supplied in environmentally friendly ways. It is, rather, embedded in the very chemistry of the process. The heat is applied to limestone, to break up its principal constituent, calcium carbonate, into calcium oxide (cement’s crucial ingredient) and CO2…

Intriguingly, this may be an area where microbes can come to the rescue….One proposal is to recruit the services of chlorophyll-laden, photosynthezing organisms called cyanobacteria. That has allowed Prometheus Materials, a firm in Colorado, to develop a cement-making process in which the energy comes not from heat but light—something easily generated from electricity that has, in turn, been provided by renewable sources. Moreover, and perhaps more importantly, photosynthesis subtracts CO2 from the atmosphere rather than adding it.…

Applications for biocement extend beyond conventional construction, too. America’s Department of Defense, for one, has shown interest. Its aim is to be able to build things in remote areas without having to hump in cement and other materials. That would be doubly valuable if the territory through which the humping would otherwise be happening were hostile. Indeed, it was the Defense Department that catalyzed the formation of Prometheus, by awarding the team at the University of Colorado which later founded the firm a grant of $1.8m back in 2017.

The department is also, in the guise of the Defense Advanced Research Projects Agency (DARPA) and the Air Force Research Laboratory, collaborating with Biomason to develop biocement sprays that can turn sand or loose soil into runways. Michael Dosier, Biomason’s chief technologist (and the boss’s husband), says the hardening involved could require less than 72 hours.

Kathleen Hicks, America’s deputy secretary of defense, during a talk at the DARPA Forward conference, outlined a goal that is literally out of this world: an ability to spray a bacterial liquid on lunar or Martian regolith, in order to “grow a landing pad”.

Excerpts Green Construction: Building with Bacteria, Economist,  Nov. 26, 2022