Mineral CO2 storage in basalts: when deep underground bacteria get involved
At a time when alternative geo-engineering solutions are multiplying to offset the excessive emissions of carbon dioxide into the atmosphere as a result of the massive use of fossil fuels (coal, oil, gas), the natural ability of basalts to mineralize CO2 into solid carbonates has long been seen as an attractive and promising avenue for long-term storage of this greenhouse gas and limiting environmental risks.
Publication date: 20/10/2017
General public, Press, Research
Related teams :
Lithosphère Organosphère Microbiosphère (LOMs)
Related themes : Earth System Science
This CO2 mineralisation capacity was recently assessed in situ in deep basaltic flows as part of the CarbFix1 project carried out in Iceland at the pilot site associated with the Hellisheidi geothermal power plant, where two injections of acid gas (CO2± H2S) were carried out in 2012.
But low-temperature basalts (< 120°C) are now recognised as one of the most important microbial habitats on Earth and host abundant and diverse microbial communities, most of which are still poorly understood. They are therefore rarely taken into account in technologies that use the subsurface for geological storage.
Since 2008, the geomicrobiology team at the Institut de Physique du Globe in Paris has been monitoring the reactivity of deep-sea ecosystems during acid gas injections in Iceland. These researchers have shown that deep ecosystems respond very quickly (within a few weeks) to injections of CO2. The acidified groundwater first of all led to a marked reduction in microbial richness and stimulated the growth of chemolithoautotrophic (CO2-using) ferroxidant bacteria and degraders of complex aromatic compounds probably produced by the dissolution of the rock. In particular, they show that the dissolution of the basalt was key to this biological stimulation by releasing the nutrients and energy sources required for the growth of these microorganisms. In turn, these microbial activities affected the redox state of the aquifer, the availability of the elements needed for carbonation and the fate of the injected carbon, with probable consequences for the efficiency of mineral storage.
For more information:
- The article published in Nature Communication: High reactivity of deep biota under anthropogenic CO2 injection into basalt
