Question

What are saline aquifers? Explain how they might be used to store carbon dioxide.

Short answer

Saline aquifers are saltwater-bearing rock formations used for storing CO2, achieved by injection and trapping through various mechanisms.

Step-by-step solution

Understanding Saline Aquifers

Saline aquifers are porous rock formations saturated with saltwater, located deep underground. They are distinct from freshwater aquifers due to the high salinity levels that make their water unsuitable for human consumption or agriculture.

Identify Attributes for Storage

These aquifers have significant storage potential due to their large volume and the ability of their porous rock to absorb and contain gases such as carbon dioxide (CO2).

CO2 Sequestration Process

The process involves capturing CO2 emissions at their source, usually from industrial processes. The CO2 is then compressed into a liquid and injected into the saline aquifer through wells.

Ensuring Long-Term Storage

Once injected, the CO2 is trapped in the rock formation through physical and chemical mechanisms such as dissolution into the saline water and mineralization, where CO2 reacts with minerals to form stable solid compounds, ensuring it does not escape back into the atmosphere.

Key concepts

Carbon Dioxide Storage

Carbon dioxide storage involves capturing CO2 emissions from sources like power plants and trapping them underground. One way to achieve this is by using saline aquifers. Saline aquifers are found hundreds to thousands of meters below the Earth's surface, where layers of porous rock are filled with saltwater.

The high salinity renders the water unsuitable for human consumption, but these formations are perfect for storing CO2. The porous nature of these rocks can hold a large amount of gas, providing a practical option for mitigating CO2 emissions.

• Saline aquifers are highly abundant globally, offering significant storage capacity.
• The geological properties of these aquifers make them an ideal option for safe and secure carbon dioxide storage.

CO2 Sequestration

CO2 sequestration is the process of capturing and storing carbon dioxide to prevent it from reaching the atmosphere. This process typically begins at the emission source, where CO2 is separated from other gases produced by industrial and energy-related sources.

Once captured, CO2 is compressed into a liquid form to facilitate its transport to storage sites. This compression contributes to the efficiency of transporting CO2, which is then injected into underground geological formations like saline aquifers.

• This method of sequestration helps reduce the carbon footprint of large emitters and combat climate change.
• Sequestration targets long-term storage solutions, ensuring trapped CO2 remains secure below the Earth's surface.

Geological Storage

Geological storage is integral to carbon capture and storage (CCS) efforts, involving the injection of captured CO2 deep underground. Saline aquifers, with their porous rock formations, serve as a promising site for geological storage.

Once CO2 is injected, several mechanisms help keep it in place. Physical trapping occurs when CO2 is confined by an impermeable layer above the aquifer, preventing it from rising back to the surface. Chemical trapping involves CO2 interaction with minerals, forming stable compounds that further secure the CO2 underground.

• Geological storage offers long-term containment, crucial for effective carbon management.
• It's a versatile solution that preserves the subsurface integrity, exploiting naturally occurring geological features.

Carbon Capture and Storage

Carbon capture and storage (CCS) is a comprehensive process involving the extraction of CO2 from emission sources and its subsequent storage in geological formations. CCS is viewed as a significant strategy in reducing greenhouse gas emissions and mitigating global warming.

The process involves three main steps: capturing CO2 emissions from industrial plants, transporting the CO2 to a storage location, and then securely storing the CO2 underground. Saline aquifers play a crucial role in the final step of this process.

• CCS helps meet the stringent emission reduction targets set globally under climate agreements.
• The technology supports industries that lack alternatives for immediate emission cuts while transitioning to cleaner energy sources.