Carbon capture and storage (CCS) is an increasingly important technology to address greenhouse gas emissions that contribute to global warming. But how exactly does CCS work?
CO2 can be stored permanently underground in geological formations like natural gas reservoirs, saline aquifers or unmineable coal beds – typically without risking leakage into shallower formations or the atmosphere. Frequent monitoring must take place to ensure the CO2 does not escape and return into shallower layers or the atmosphere.
What is Carbon Capture and Storage?
Carbon Capture and Storage (CCS) technology captures CO2 before its release into the atmosphere from industrial flue gases, before it’s stored permanently away in geological formations like saline aquifers or depleted oil and gas reservoirs for long-term removal from the carbon cycle.
CCS technology can be applied to both fossil and renewable energy production processes to reduce greenhouse gas emissions and achieve their common goal of reduced emission levels.
Presently, five CCS facilities are operating worldwide on a commercial scale; two use post-combustion capture while others use precombustion or oxy-fuel capture methods.
Bioenergy with Carbon Capture and Storage (BECCS) combines CCS with biomass energy production in order to remove CO2 from the atmosphere while producing renewable power, while at the same time providing net zero carbon electricity. It operates similarly to a coal-fired power plant but may differ due to differences in biomass composition and properties.
Why is Carbon Capture and Storage Important?
CCUS technology helps power plants and industrial facilities prevent their carbon dioxide (CO2) emissions from being released into the atmosphere, as well as mitigate historical CO2 emissions by capturing and storing CO2 through point source technologies such as direct air capture and storage (DACCS) or bioenergy with carbon capture and storage (BECCS).
CCS systems can be complex, and each step in their creation — such as collecting, transporting and storing — often is owned and run by different entities, making coordination challenging.
CCUS is costly, energy intensive and limited in scale; many community organizations and advocates view it as an expensive band-aid for polluting industries that pose health and environmental risks to marginalized communities. Furthermore, at a time when renewables such as wind and solar are becoming cheaper still, CCUS serves to secure fossil fuel production – an obstacle to rapid decarbonization goals of our generation.
What are the Solutions to Carbon Capture and Storage?
There are various technologies that could aid carbon capture and storage efforts. Post-combustion carbon capture utilizes chemical solvents that separate CO2 from flue gases at fossil fuel power plants or other point sources of emissions, often as part of retrofit projects at existing plants. Oxyfuel carbon capture requires burning fossil fuel in pure oxygen in order to facilitate separation of the CO2.
Captured carbon dioxide must then be purified and liquefied prior to transport. Over 4,500 miles of pipelines already carry CO2 for enhanced oil recovery in the United States alone, yet this technology could easily scale to larger capacities.
Once liquefied, carbon dioxide can be safely stored underground for long-term storage. The United States has over four decades of experience using this technique for oil and gas field EOR operations and new projects can build on that knowledge base.
Carbon dioxide can also be utilized for other uses, including manufacturing and industrial processes. This practice, known as carbon dioxide utilization, may reduce greenhouse gas emissions if they replace other forms of energy such as fossil fuels.
What are the Challenges to Carbon Capture and Storage?
Carbon Capture and Storage involves complex engineering to prevent CO2 emissions from power plants and other industrial sources from being released into the atmosphere. Once captured, CO2 is transported via pipeline or ship to sites where it will be permanently stored within deep geological formations such as depleted oil fields or saline aquifers for permanent storing; all while being closely monitored to prevent it leaking into shallower formations or the atmosphere.
Compressing and chilling the CO2 requires considerable energy consumption, making this form of carbon capture and storage (CCS) less sustainable as an approach to climate change mitigation.
Recent permit rejections for two high-profile pipeline projects in the US Midwest signal growing public opposition to carbon capture and storage (CCS), due mainly to its need for additional infrastructure to transport and store CO2. It would also not align with environmental justice principles as it would pose additional risks and hazards on communities already burdened by fossil fuel pollution.