Carbon Capture and Storage

How It Works


Potential Uses and Concerns


Carbon Capture and Storage in Iceland’s Basaltic Bedrock

Iceland is known for its renewable-based energy economy, partly derived from its proximity to the mid-Atlantic rift, which provides a source for geothermal energy (find out more here). Its geologic setting (read more here) also provides opportunity for another advance in sustainability: carbon capture and storage (CCS). Carbon capture and storage refers to the process of capturing carbon dioxide from the atmosphere or power plants and injecting it into rocks containing magnesium-, iron- and calcium-rich minerals (Fountain 2016). Iceland’s balsaltic rock formed by cooling of upwelled magma in the Atlantic spreading center is rich in these minerals, which mineralize carbon by reacting with CO2 to form carbonates. The process of CCS is considered a promising strategy for storing carbon dioxide produced by the burning of fossil fuels in order to curb greenhouse gas emissions and mitigate global climate change (Stephens 2009).

How it works

Matter et al. 2016 pioneered a method for CCS in 2012 involving the following steps:
1.    Collection. Carbon dioxide was collected from the geothermal power plant adjacent to the injection site.
2.    Dissolution. The captured CO2 was dissolved in water (similar to soda water) in order to aid the transfer of CO2 into the ground.
3.    Injection. In one experiment, 175 tons of pure CO2 gas was injected. In another experiment, a 73-ton mixture of CO2/H2S gas was injected. It is     important to understand how H2S gas affects the injection process because CO2 gas produced during fossil fuel combustion often contains H2S, which would be costly to remove from the captured CO2 gas.
4.    Target Rock. The oxygen-depleted water, which was 20-33˚C and pH of 8.4-9.4, had an intended target rock of basaltic lavas and hyaloclastites at 400-800 m depth.

This cross section shows the depth and bedrock type where CO2 and H2S were injected.

5.    Mineralization. The carbon dioxide then reacted with the Ca-Mg-Fe rich minerals to create carbonate rock, thereby mineralizing the carbon

The scientists used 14C to trace the amount of CO2 gas that was mineralized by measuring the 14C/12C ratio in the reservoir throughout the experiment.  They also used SF6CF3 and SF6 to monitor the movement of injected liquid through the reservoir: when these sulfur species were measured in a monitoring well, it was understood that the injected fluid had reached the well site (Matter 2014).


Analysis of these tracer concentrations showed that >95% of the CO2 was mineralized within two years, further confirmed by the clogging of the injection pump by carbonates and by analysis of altered basalt grains in the injection area, which show the formation of carbonate minerals, seen in figure 2.

The image on the left shows palogonite, which is an alteration product from the interaction of water with volcanic glass of chemical composition similar to basalt. In the second picture, calcite is visible, which shows that some of the carbon dioxide reacted with calcium-rich minerals to form carbonate rock.

Through this experiment, Matter et al. confirmed the possibility of using this site in Iceland to store CO2 and H2S through rapid mineralization (Matter 2014). A core of the bedrock near the injection site confirms the presence of the precipitated carbonates (Zielinski 2016):

This section of the rock core has mineralized carbon (the white carbonate) embedded in the basalt.

Potential Uses and Concerns

This method of carbon dioxide injection and mineralization could provide a method for the storage of anthropogenically emitted CO2, which would combat the continued warming of the climate due to increasing greenhouse gas emissions (Zielinski 2016). The conversion of CO2 to carbonate minerals is rapid and reliable, making the need for monitoring minimal in comparison to other CCS techniques (Stephens 2009).

Although the first experiment performed by Matter et al. was successful, the process would need to be performed on a much larger scale in order to impact global CO2 concentrations. Increasing the scale of this process causes several complications in the viability of the injection and mineralization. First, the process requires large quantities of water: every ton of carbon dioxide must be dissolved in 25 tons of water before injection (Gislason 2014). This problem can be minimized by the usage of seawater, which is viable according to the researchers, but it would still take ample resources to transport and inject 25 tons of the solution. Second, the process requires a specific kind of rock: the material receiving the injection must be a Ca-Fe-Mg rich basalt, which limits the possible injection sites to areas containing this form of bedrock. However, estimates of the amount of basalt in all of the mid-ocean ridges indicate that this could provide enough material to store an order of magnitude more carbon dioxide that has been emitted by fossil fuel burning (Gislason 2014). Thirdly, CCS is expensive: it costs about $17/ton of CO2 (Gislason 2014). Finally, in order to mitigate climate change caused by previously emitted fossil fuel carbon dioxide, a technology would need to be developed to capture enough carbon dioxide to contribute to reducing CO2 concentrations in the atmosphere to pre-anthropogenic levels. We currently do not have the technology to capture atmospheric carbon dioxide in an energy efficient and affordable way, which will limit the efficacy of the CCS technique tested in Iceland. However, if these obstacles can be overcome through new technologies and discoveries, then this method of CCS could provide a bridge between the current fossil fuel energy structure and the future of renewable energy (Zielinski 2016). It cannot be considered the silver bullet to solving climate change, but it can be part of a portfolio of solutions that will ultimately lead to a greener future (Stephens 2009).


Fountain, Henry. “Iceland Carbon Dioxide Storage Project Locks Away Gas, and Fast.” The New York Times, The New York Times, 9 June 2016,

Gislason, S. R., and E. H. Oelkers. “Carbon Storage in Basalt.” Science, vol. 344, no. 6182, 2014, pp. 373–374., doi:10.1126/science.1250828.
Matter, Juerg M., et al. “Rapid Carbon Mineralization for Permanent Disposal of Anthropogenic Carbon Dioxide Emissions.” Science, American Association for the Advancement of Science, 10 June 2016,

Matter, Juerg M., et al. “Rapid Carbon Mineralization for Permanent Disposal of Anthropogenic     Carbon Dioxide Emissions.” Science, American Association for the Advancement of     Science, 10 June 2016,

Stephens, Jennie. “Assessing Innovation in Emerging Energy Technologies: Socio-Technical Dynamics of Carbon Capture and Storage (CCS) and Enhanced Geothermal Systems (EGS) in the USA.” Energy Policy, Elsevier, 29 Dec. 2009,

Zielinski, Sarah. “Iceland Carbon Capture Project Quickly Converts Carbon Dioxide Into Stone.”, Smithsonian Institution, 9 June 2016,

By: Ursula Jongebloed