Options for permanent CO2 storage
Permanently storing captured CO2 is a key element of carbon management strategies. There are several established and emerging methods to sequester CO2 for long durations.
Geological storage
- Saline aquifers: deep underground rock formations filled with salty water can hold large volumes of injected CO2 and are widely available globally.
- Depleted oil and gas reservoirs: these formations have geological seals and infrastructure knowledge, and they can store CO2 safely when monitored.
- Basalts and other reactive rocks: CO2 injected into reactive rock formations can mineralize more quickly into stable carbonates.
Mineralization
- In-situ mineralization: CO2 reacts with subsurface minerals to form solid carbonates, locking carbon into rock.
- Ex-situ mineralization: CO2 is mineralized into building materials or industrial products like cured concrete or aggregates.
Marine and other methods
- Sub-seabed storage: using offshore geological formations similar to onshore saline aquifers in suitable locations.
Key considerations for permanent storage
- Integrity and monitoring: sites are selected for geological stability and capped by impermeable layers; continuous monitoring ensures CO2 remains contained.
- Capacity and longevity: many formations offer gigaton-scale capacity, but proper assessment and regulation are essential.
- Environmental risks: site characterization and best practices minimize risks of leakage and other impacts.
Regulatory and social aspects
Regulations, liability frameworks, and community engagement are critical for public acceptance and long-term stewardship of storage sites. Clear rules for monitoring, reporting, and verification (MRV) ensure environmental safety.
Conclusion
Geological storage in saline aquifers and depleted reservoirs, along with mineralization into stable materials, are the primary pathways for permanent CO2 sequestration. Proper site selection, engineering, and monitoring are essential to ensure permanence and safety.