Carbon Capture and Storage (CCS) is one of the many technologies being explored to mitigate greenhouse gas emissions from fossil fuels, with long-term disposal taking place underground in geologic formations.
CCUS involves extracting CO2 from power plants or industrial facilities, compressing it, transporting it to storage sites in porous rock formations such as depleted oil and natural gas reservoirs or saline aquifers and then storing it permanently there. At present, 29 CCS projects are operating, while another 143 are in various stages of development.
Capture
Carbon capture and storage technology provides one solution to curb greenhouse gas emissions from fossil fuel-fired power plants by collecting CO2, before it enters our atmosphere, for storage or incorporation into products.
CO2 can be extracted from fossil fuels both before and after combustion (pre- and postcombustion), using various processes involving chemical transformations to capture it for permanent storage at a CCS site.
CCS processes may use either biological or geological means of sequestering carbon dioxide, depending on how CO2 is collected and stored. For instance, biological carbon sequestration involves sequestering it in natural environments like forests, soils and oceans, often known as carbon sinks; while geological carbon sequestration involves burying captured CO2 deep underground.
Compression
At least 26 large scale carbon capture projects are operating worldwide today, while others are in early development or advanced front end engineering design stages. Once captured, CO2 captured by these systems is then transported via pipeline to storage sites for permanent storage.
Compressing CO2 into liquid form for transport requires significant energy inputs and requires large, costly facilities and equipment that must be constructed and operated in order to be successful.
Once at its storage site, CO2 is injected deep underground into geological formations such as old oil and gas reservoirs or saline aquifers – this process is known as utilization; hence CCUS stands for carbon capture, utilization and storage). Most current CCS strategies call for utilization as one approach, yet this poses risks associated with investing in emissions-intensive industries which displace other jobs while potentially creating greater harms than benefits to communities.
Transport
Existing facilities equipped with carbon capture can capture approximately 90% of the CO2 found in flue gas emissions.
Captured carbon can be put to use in various applications, including product formulation or long-term storage. One popular way of using captured CO2 is enhanced oil recovery (EOR), wherein CO2 injection increases pressure within aged oil reservoirs in order to extract more crude oil.
CO2 produced from emissions is compressed and then transported by pipeline, ship or rail to an appropriate storage site for long-term storage. Transportation costs depend on how far away from emission sources you are; designing optimal carbon capture supply chains to enable long-distance deployment is essential to make technology suitable for storage viable.
Utilization
Carbon capture and storage involves collecting relatively pure streams of CO2 from power plants or industrial facilities, transporting it long distances, and depositing it deep geological formations for permanent storage. This technology has proven particularly successful when applied to coal-fired power generation, ethanol production, natural gas processing, refinery hydrogen production, etc.
While carbon capture technology may help lower greenhouse gas emissions from polluting industries, it cannot be seen as an effective means of reducing global emissions. Instead, many view it as providing fossil fuel companies with the green light to keep operating and increase production.
Most CCUS projects utilize captured carbon dioxide for commercially viable purposes, such as producing concrete sand or chemicals such as methanol. Some large-scale projects also employ CO2 for enhanced oil recovery (EOR), though this strategy doesn’t count towards climate change mitigation.
Storage
Carbon capture and storage (CCUS) technologies capture CO2 from emissions sources before it enters the atmosphere, with captured CO2 either stored underground permanently or used as raw material for products like concrete and chemicals production.
At present, approximately 30 commercial CCS projects are in operation globally. Most use carbon dioxide injection into oil reservoirs to enhance oil recovery; after which, its carbon dioxide content is separated and pumped underground for permanent geologic storage in depleted oil fields, coal beds or saline aquifers.
CCUS systems can be costly and time-consuming to develop, with heavy upfront costs and risks making implementation more complex than other clean energy technologies. Yet despite these hurdles, CCUS can have substantial climate benefits by decreasing our dependency on fossil fuels.