A soil-dwelling microbe has shown a surprising ability to trap carbon dioxide and turn it into rock. Scientists have discovered that Bacillus megaterium, a common bacterium long known for its role in biotechnology, can convert CO₂ gas into solid calcium carbonate with an efficiency rarely seen in either nature or industry. The process, recently detailed in a study led by researchers at the Swiss Federal Institute of Technology Lausanne (EPFL), could change the future of carbon capture and help reduce emissions from major industrial sources.
Limestone Made By Microbes In Pressure Chambers
Inside pressurized laboratory flasks—holding CO₂ gas at more than 470 times atmospheric pressure—Bacillus megaterium formed calcium carbonate crystals by pulling more than 94 percent of the carbon directly from the gas. According to lead author Dimitrios Terzis of EPFL’s Soil Mechanics Laboratory, this performance outpaces most engineered carbon-sorbing materials.
The microbe’s impressive efficiency makes it a strong candidate for point-source carbon capture, especially at polluting facilities like cement kilns and steel plants. Because the bacterium uses a biological pathway that avoids toxic byproducts, it may offer a more sustainable alternative to current technologies.
Bypassing Ammonia With A Cleaner Process
Bacillus megaterium usually works with a pathway called ureolysis, which splits urea to raise pH and drive calcite formation—but this route produces ammonia, a compound requiring expensive treatment. In this study, scientists observed that at high CO₂ concentrations, the bacterium switched to a different enzyme: carbonic anhydrase.
This enzyme hydrates carbon dioxide to form bicarbonate, which reacts with calcium to produce solid rock without ammonia. The study confirmed that only six percent of the carbon in the calcite came from urea, indicating a nearly complete shift to the cleaner route. Researchers believe this “metabolic flip” could serve as a biological shut-off valve for ammonia emissions.
Since both urease and carbonic anhydrase sit in the periplasm—the space between the bacterial membranes—carbon dioxide and urea don’t need to enter the cells, speeding up the process and allowing fine control of the reaction through gas or nutrient flow.
How Bacteria Could Transform Cement for Good
The cement industry is a major carbon emitter, responsible for around 8 percent of global CO₂ emissions—nearly three billion tons each year. Finding low-carbon alternatives to traditional cement is one of the toughest challenges in climate mitigation.
The idea of partially replacing cement with bio-grown calcite has become more attractive in this context. Not only does the process remove CO₂ from the air, but the resulting mineral is durable and stable over geological timescales. That makes it suitable for construction and long-term carbon storage.
Pilot studies in Denmark showed that concrete fortified with this microbial calcite retained more than 98 percent of its compressive strength after 300 freeze-thaw cycles. These durability benchmarks are critical as building codes increasingly prioritize materials with both low emissions and long service lives. Regulatory agencies in California and the European Union are already moving toward performance-based codes.
From Lab To Large-scale Carbon Storage
The startup Medusoil—involved in the study—has already built pilot bioreactors that inject Bacillus megaterium into crushed rock to produce load-bearing blocks. The company says its system captures several pounds of CO₂ per cubic foot of treated material, creating stone from gas within hours.
At Newcastle University, researchers recently inserted the carbonic anhydrase enzyme from B. megaterium into another species, Bacillus subtilis, and achieved a nearly 80 percent CO₂ reduction in flue gas tests. This suggests that modular biological components could be plugged into different microbial hosts for varied industrial settings.
Cost estimates suggest that when powered by renewable electricity, these microbial systems could remove carbon for less than $50 per metric ton—competitive with traditional chemical scrubbers. Calcium, needed for the reaction, could come from waste sources like mine tailings, recycled concrete, or desalination brines, easing the environmental burden of raw material extraction.
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