Using bacteria to decrease CO2 levels
Carbon capture and storage (CCS) is a promising method to reduce CO2 levels in the atmosphere, and scientists are looking at different approaches for achieving this. One possibility is to use the natural ability of certain bacteria to convert calcium and CO2 to CaCO3. Scientists initiated the EU-funded CO2SOLSTOCK (Biobased geological CO2 storage) project to find ways of using bacteria to precipitate carbonates, in order to store CO2 in a solid form. CO2 sequestration in the form of CaCO3 would also free CCS from the current restrictions to deep underground storage. Scientists explored several pathways for achieving CaCO3 precipitation using bacteria. The most promising was the oxalate-carbonate pathway, in which bacteria use the chemical oxalate from trees (e.g. Iroko tree) to increase soil pH and precipitate CaCO3. In addition, they showed that the pH shift in soil required for precipitation of CaCO3 depends on the simultaneous presence of fungi, bacteria and oxalate. This system occurs naturally in dry areas of western Africa, Bolivia and India and has been trialled successfully as part of agro-forestry projects in Haiti. Another approach used industrial by-products (wastewater with desalination brine or silicate rocks) as carbon and calcium sources. CO2SOLSTOCK found some success with this approach, but further work is needed to optimise the process. CO2SOLSTOCK results demonstrate the promise of bio-based carbon sequestration through the use of carbonate-forming bacteria. Combining CCS with reforestation efforts offers an exciting new approach to climate change mitigation.
Keywords
Bacteria, calcium carbonate, carbon capture and storage, geological, CO2 storage
