Direct Air Capture + Storage

Many major scientific assessments have now concluded that the world will need large quantities of carbon dioxide removed from the atmosphere if we are to avoid the worst impacts of climate change. Direct Air Capture with geological storage is one of very few tools that can deliver permanent carbon removal at gigaton-scale.

About Geological Storage

Geological storage is the process of injecting and storing CO2 deep underground in geological reservoirs.

Geological carbon dioxide storage, also known as carbon sequestration, has been used safely and effectively by industry for decades, with more than 200 million tonnes of CO2 successfully stored in geological sites all over the world. Leading international bodies, such as the Intergovernmental Panel on Climate Change (IPCC), have assessed this practice and concluded that when storage sites are properly regulated, selected, and managed, CO2 can be stored permanently for millions of years with very low risk. Suitable locations for carbon storage exist in many regions around the globe and collectively have the capacity to store hundreds of years of CO2 emissions underground.

Pairing Direct Air Capture with geological storage is a logical, safe, and reliable way to permanently remove vast amounts of CO2 from the atmosphere. Traditional use of fossil fuels extracts carbon from underground geological reservoirs. When used in our cars, homes, or power plants, the carbon is released into the air in the form of CO2, thus driving climate change. Direct Air Capture with secure geological storage can do exactly the reverse. By capturing atmospheric CO2 and permanently storing it underground, this form of carbon removal, or negative emissions, can be used to counteract emissions that are occurring elsewhere.

How Geological Storage Works

The captured CO2 is compressed into a fluid almost as dense as water and injected deep underground to the geological reservoir through a secure and highly engineered well. At the top of the geological formation is a cap rock, an impermeable rock layer that acts as a permanent barrier so the CO2 cannot return to the surface.

Over time, the CO2 will interact with the water and rock within the reservoir, becoming trapped there through the following processes:

Solution Trapping: CO2 dissolves into saline water in the reservoir, becoming a part of the reservoir fluids trapped under the cap rock
Residual Trapping: CO2 is trapped in the millimetre-sized voids, or pore spaces
Mineral Trapping: CO2 interacts with the reservoir rocks to form new minerals, permanently trapping the CO2 in the rock
Key Features of DAC With Geological Storage
Permanent
Direct Air Capture with geological storage offers a permanent solution for removing CO2 from the atmosphere. When geological storage sites are properly regulated, selected, and managed, the CO2 injected can be stored permanently for millions of years (Source: IPCC).
Measurable and verifiable
The amount of CO2 captured by Direct Air Capture is precisely measured and a variety of monitoring technologies have been successfully deployed over decades of geological storage experience, ensuring the quantity of CO2 permanently stored is measured, monitored, and verified.
Safe
Geological storage is a safe and reliable form of storing CO2 deep underground. It is a well-established practice that is highly engineered and strictly regulated, and has been in safe, commercial operation for decades.
Types of Storage Options
01

Standalone Geological Storage

Captured atmospheric CO2 can be securely stored in saline formations or depleted oil and gas wells to deliver permanent carbon removal.

Saline Formations are large layers of rocks with porous spaces that are isolated deep underground and contain salt water. The practice of storing CO2 in saline formations has been examined extensively by industry, academics, and government agencies and has been found to present a long-term solution for CO2 storage with immense capacity.

Depleted oil and gas fields that are no longer productive also make ideal geological storage sites due to their established trapping and storage characteristics and the availability of extensive geologic data from when they were operational wells.

Permanently storing atmospheric CO2 in saline formations and depleted oil and gas wells allows us to achieve what is known as carbon dioxide removal, or negative emissions. A Direct Air Capture facility built this way has the sole purpose of removing CO2 from the atmosphere. Near-term, this will allow us to reduce the net amount of CO2 that is being released into the atmosphere and help us get to net zero much faster. In the future, once CO2 emissions have been reduced dramatically, these facilities could be used to reduce the overall level of CO2 in the air back to safe levels.

Standalone Geological Storage
02

Enhanced Oil Recovery

Atmospheric CO2 captured from DAC plants can be permanently stored in oil reservoirs during oil production.

Injecting CO2 into oil reservoirs is a common practice, known as enhanced oil recovery, that has been performed by the oil and gas industry since the 1970’s. While historically enhanced oil recovery was not performed to achieve environmental benefits, when the CO2 used has been removed from the atmosphere using Direct Air Capture technology, it can dramatically reduce the overall carbon footprint of the oil produced.

Additionally, new laws and regulations – such as California’s Low Carbon Fuel Standard – are now giving guidance and incentive to experienced operators to ensure the CO2 is stored permanently during the process. When performed this way, the permanent injection of atmospheric CO2 into the reservoir can partially or completely counteract the emissions from the oil produced. Or, if the quantity of atmospheric CO2 permanently stored is greater than what is produced through refining and use of the oil, this activity can produce fuels for transportation while also generating net negative emissions. For readers familiar with life-cycle analysis, this means that, depending on factors such as the pattern of the well and the operation of the oil reservoir, DAC with enhanced oil recovery can produce fuels with low, zero, or even negative life-cycle “carbon intensity”.

Enhanced Oil Recovery
If the amount of CO2 injected and stored is equal to the amount produced when the oil is refined and used, the full process is carbon neutral. If more CO2 is injected than what is produced, the process results in a net reduction of CO2 in the atmosphere.
Carbon Engineering's pilot DAC facility in Squamish, BC.

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