Engineered Bacteria Triple the Speed of Rock Weathering for Carbon Capture

Genetically modified marine bacteria can accelerate the natural breakdown of silicate rocks by a factor of 2.6, compressing a geological carbon-capture process into a timeframe that could meaningfully offset modern emissions. In a pilot-scale study published in August 2026, researchers demonstrated that the engineered microbe Alteromonas macleodii continuously weathered 4 kilograms of the mineral olivine in seawater bioreactors, removing 0.50 grams of carbon dioxide from the air per day. The findings establish a biological mechanism to fast-track one of Earth's oldest climate thermostats.[1][4][5]

The mechanism relies on overcoming a chemical bottleneck that normally halts rock dissolution. When silicate minerals like olivine interact with water and air, they dissolve and release magnesium, iron, and silicate, a reaction that converts dissolved carbon dioxide into stable bicarbonate. However, the released iron quickly oxidizes when exposed to the atmosphere, forming a rust-like crust over the mineral surface. This iron oxide layer acts as a physical barrier, severely slowing the rate at which the rock can continue to draw carbon from the water.[2][4]

To bypass this passivation layer, a collaborative team from the Wyss Institute at Harvard University, Harvard Medical School, and the Stanford Doerr School of Sustainability turned to siderophores. Siderophores are specialized molecules secreted by certain microorganisms to bind and extract iron from their environment. By capturing the oxidized iron and solubilizing it, these molecules effectively de-rust the mineral surface, exposing fresh olivine to the seawater and allowing the weathering cycle to continue uninterrupted.[1][3]

The researchers, led by chemical engineer Neil Dalvie alongside principal investigators Pamela Silver and Michael Springer, specifically targeted Alteromonas macleodii, a widespread ocean bacterium. While natural bacteria produce siderophores, they typically stop secreting them once they detect sufficient iron in their surroundings—a genetic regulation that prevents continuous rock weathering. The team edited the bacterium's genome to disable this feedback loop, forcing the microbes to overproduce siderophores regardless of ambient iron concentrations.[1][4][5]

"Some people describe rock weathering as a silver bullet for climate change. The problem is that it's too slow," said Dalvie, a synthetic biology fellow at Harvard Medical School. "We've found a way that it could work, and, maybe more importantly, now we have a model to calculate what it would look like to implement this at scale."[5]

The team validated the engineered strain in continuous-flow mineral bioreactors designed to mimic coastal deployment conditions. Untreated seawater was pumped through the system at a rate of 1.5 liters per day, alongside a renewable acetate feedstock to sustain the bacterial population. Over a 72-hour steady-state period, the modified microbes increased the dissolution rates of silicon, iron, and nickel from the olivine substrate by nearly threefold compared to control tanks containing unmodified bacteria.[4][5]

The resulting chemical shift directly impacts carbon sequestration capacity. As the olivine dissolves faster, it generates alkalinity in the seawater. This alkaline shift allows the water to absorb more carbon dioxide from the headspace of the reactor, trapping it as dissolved bicarbonate. In the pilot system, the 2.6-fold increase in weathering translated directly to the measured removal of 0.50 grams of atmospheric CO2 daily, proving that the biological intervention scales to actual carbon drawdown.[2][4]

Enhanced rock weathering is already being pursued by several climate technology companies, which typically scatter crushed silicate rocks over agricultural land or coastal waters. While the approach is considered safe and relies on abundant materials, the natural dissolution rate means it could take decades to see a return on the energy invested in mining and transporting the rock. By integrating synthetic biology, facilities could theoretically process the same volume of rock in a fraction of the time, requiring smaller physical footprints and generating faster carbon credits.[1][2]

Scaling the technology from a 4-kilogram laboratory reactor to an industrial facility will require addressing the logistics of microbial maintenance. The researchers' life-cycle analysis indicates that the system's net carbon benefit depends heavily on using renewable feedstocks to feed the bacteria and minimizing the need to continuously replenish the engineered cells. The pilot reactors demonstrated that the bacteria form stable biofilms on the olivine surfaces within three weeks, suggesting they can maintain themselves in a continuous-flow environment with minimal intervention.[4][5]

The next phase of development involves moving beyond controlled laboratory seawater to larger, open-system trials to assess ecological interactions. While Alteromonas macleodii is native to the ocean, deploying genetically modified strains at an industrial scale requires stringent containment protocols or built-in genetic kill switches to prevent unintended environmental consequences. The current bioreactor model keeps the process contained, offering a controlled environment where the accelerated weathering can be measured and verified before the alkaline water is released back into the ocean.[2][4][6]