Image of a core from CarbFix site at CarbFix project, Orkuveita Reykjavikur
Carbon dioxide is a waste gas product produced by the burning of fossil fuels such as oil and coal that is contributing to the greenhouse effect and global warming. But Icelandic company Carbfix have developed a process to turn the waste gas from our atmosphere back into stone and bury it permanently underground. A solution that could be the answer to reaching climate goals set by the UN in the 2015 Paris Agreement.
Carbfix, a project started in 2006 by founding partners including the University of Iceland and the Earth Institute at Columbia University, offers storage potential on a global scale via carbon mineralization in rocks such as basalt that could potentially exceed anthropogenic emissions. The process involves taking carbon dioxide, dissolving it to a fluid in pressurized water and injecting it into underground rock formations where a chemical reaction will take place to turn up to 95% of the CO2 back into rock in under 2 years. Almost 87,000 tonnes of CO2 have been injected into the ground since 2014 with plans to develop the process globally and greatly increase this number in the not-too-distant future.
The science behind this process is relatively simple. The fluid containing dissolved carbon dioxide is injected into specific rocks such as basalt which contain metal ions that react with the fluid to form carbonate minerals. This is essentially nature’s way of storing carbon in rocks but accelerated, providing a safe method of permanent carbon storage. The geology required for this process is different for what is needed for conventional carbon capture and storage (CCS) methods meaning there is potential for development in places previously thought to be unfeasible for carbon storage. Basalt, the primary rock type used by Carbfix, is the most abundant rock type on the planet, being the primary constituent of oceanic crust. Basalts contains up to 25% calcium, magnesium, and iron (metal ions that react with the carbonated fluid to produce carbonate rocks) as well as often being fractured and porous allowing for storage space of the newly mineralized carbonates.
Carbonate rock storage of carbon dioxide has plenty of future potential to help us meet global climate goals but as with all developing technology there are other impacts that need to be considered. A large amount of water is required in order to dissolve and inject the carbon dioxide into the rocks as well as to facilitate the reactions that occur. This water is currently being sourced from the rocks that it will then be injected back into to so there is some extent of water recycling. However, to improve sustainability and limit water loss, tests are underway on using seawater instead of underground freshwater in the process. This could also enable storage in places where the geology does not contain sufficient amounts of freshwater. The potential of groundwater contamination is also a worry and with the process being relatively new this is needing to be carefully monitored. This being said, the carbon dioxide injected water is denser than typical groundwater so sinks down relative to the water table resulting in limited interaction between the two. This means that water contamination is not a prominent issue with the process. Another potential worry related to any ground injection based processes is seismic activity. Monitoring of the injection sites is taking places prior to, throughout and after the drilling and injection processes in order to locate and minimize any issues.
As with many chemical processes, the pressurisation of the carbon dioxide gas in order to dissolve it in water without any heating requires energy. About 75kWh is needed to dissolve 1 tonne of CO2, approximately the same amount needed to power a desktop computer for 20 days. At the Carbfix operations taking place in Iceland this energy is provided by geothermal power plants attached to the process, making the energy production a clean source (not emitting any carbon dioxide itself). This approach could potentially be replicated elsewhere in the world with other forms of renewable energy and a project funded by EU’s horizon 2020 programme is aiming to develop four more plants in Iceland, Turkey and Germany.
The future of Carbfix and carbonate based storage is looking bright and with the agreement that CCS is necessary to reach climate goals set by the UN in the 2015 Paris agreement it may be a large part of what is needed to limit global temperature rise. Potential for implementation of the process has been identified in over ten countries including the USA, Japan and the Philippines with a capacity of up to 400 billion tonnes theoretically available at the Icelandic oceanic rift zone alone. The capacity of storage world wide is far larger than what is needed to surpass climate goals and along with the potential use of a similar process to remove and store hydrogen sulphide from our atmosphere in the same way are meaning limiting global temperature rise is finally looking to be within our reach.
Source:
https://www.carbfix.com/ and associated research papers linked on the website
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