Exploring Subsea Volcanoes: A Path to Net-Zero Carbon Emissions
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Subsea Volcanoes: A Potential Solution for Carbon Storage
Recent research indicates that underwater volcanoes could serve as significant reservoirs for carbon dioxide, potentially aiding in the quest for net-zero emissions. With billions of dollars being invested in carbon capture technologies, the critical question remains: where can we securely store this captured carbon? New findings suggest that dormant subsea volcanoes may hold the key to safely sequestering vast quantities of carbon dioxide for extended periods.
In particular, a study zeroed in on the Fontanelas volcano, located about 100 km off the coast of Lisbon, Portugal, with its summit resting 1,500 meters beneath the ocean's surface. This site was selected due to its rich existing data, its optimal geological structure for carbon storage, and its distance from densely populated regions.
Utilizing both 2D and 3D seismic imaging collected during prior oil exploration and data from a 2008 dredging project, researchers mapped the volcano's geological characteristics. Analysis of the dredged materials revealed a significant presence of carbonate minerals and confirmed that the igneous rock comprising the volcano has a porosity of 40%. This porosity indicates ample space within the structure to accommodate injected carbon dioxide. Additionally, the low-permeability layers surrounding the volcano serve as seals, keeping the carbon securely contained within the porous interior.
Based on their findings, the researchers estimate that this dormant volcano could potentially store between 1.2 and 8.6 billion tonnes of carbon dioxide. But how does this process work?
In Situ Mineral Carbonation Explained
Under specific conditions—particularly high pressure and temperature—certain rock types can react with carbon dioxide. This reaction occurs in environments akin to geological hot springs or volcanic regions. Rocks rich in calcium, magnesium, and iron bond with carbon dioxide to form stable carbonate minerals like calcite, dolomite, and magnesite. These minerals can remain intact for millions of years, effectively locking away the carbon dioxide.
The carbonate minerals discovered in the samples indicate that this mineralization process is already taking place naturally within the Fontanelas volcano. The porous nature of the rock allows for the injection of carbon dioxide, while the surrounding low-permeability layers act as barriers, ensuring the gas remains long enough to react and form stable minerals. Furthermore, as the volcano is extinct, it is unlikely that these minerals will degrade and release the sequestered carbon in the foreseeable future.
While this method is not new—companies like CarbFix and Climeworks are already employing it—most current practices involve injecting carbon dioxide into sedimentary basins, which tend to have lower pressure and temperature than volcanic environments. Consequently, the mineralization reaction is slower. However, studies have shown success, with CarbFix mineralizing 95% of the injected carbon dioxide within two years.
The Need for Faster, More Efficient Storage Solutions
Currently, we are only capturing approximately 0.0426 gigatonnes of carbon dioxide annually. To effectively combat climate change, we need solutions that can store billions of tonnes of carbon. The research underscores that extinct volcanoes could provide a viable alternative.
Interestingly, the Fontanelas volcano is not unique; similar geological structures are abundant. It is estimated that there are around 75,000 subsea volcanoes exceeding 1 km in height, the majority of which are dormant. Collectively, these volcanoes could potentially store up to 322,500 gigatonnes of carbon dioxide!
At present, humanity emits about 36 gigatonnes of carbon dioxide each year, which means theoretically, utilizing these underwater volcanoes could offset emissions for nearly 9,000 years. However, transitioning to low-emission technologies would likely reduce our annual need for carbon storage to around 10 gigatonnes, enabling us to achieve net-zero emissions for over 32,000 years.
Challenges Ahead
Despite this encouraging outlook, it remains uncertain whether all these volcanoes possess the same structural characteristics as Fontanelas, which are essential for effective carbon storage. Many may lack the necessary porosity, mineral composition, or sealing layers to prevent carbon dioxide from escaping.
Nonetheless, it is not essential for every volcano to meet these criteria; a sufficient number of suitable sites could enable us to reach net-zero emissions. However, scaling carbon capture technology to this extent presents significant challenges, as does the infrastructure needed to transport captured carbon to these volcanoes. This may involve developing extensive pipeline networks or innovative ocean-based carbon capture solutions.
In conclusion, this study illuminates a promising avenue for practical carbon capture, addressing previous uncertainties about secure long-term storage. By advancing carbon capture technology and significantly reducing emissions, we can work towards achieving net-zero emissions and potentially avert the climate crisis.
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