Carbon capture and storage (CCS) is one of the core technologies required for reaching net zero emissions, consisting of underground capture of fossil fuel emissions for long-term storage.
CO2 can then be injected into geological formations such as saline aquifers or depleted oil and gas reservoirs hundreds of feet underground, to make an environmental statement about global climate change.
Capture
Carbon Capture and Storage (CCS) technology aims to reduce greenhouse gas emissions from power plants and industrial processes by collecting CO2 at the point of emission, transporting it over distances, and depositing it permanently in deep geological formations.
Capturing CO2 involves various technologies, including post-combustion capture at coal and natural gas power plants, pre-combustion capture in industrial facilities and oxy-fuel combustion. Each has their own set of challenges; nonetheless they all advance rapidly towards meeting global climate goals.
Captured CO2 can be put to many uses, from enhanced oil recovery (EOR) and producing building aggregates, to providing enhanced oil recovery (EOR), but none provide net climate benefits after considering indirect and other effects – which explains why most CCS projects under development involve dedicated underground storage of captured CO2. However, some CO2 could also be utilized in ways which do have net climate benefits, such as manufacturing products and industrial materials using captured CO2.
Compression
Carbon capture and storage technologies allow power plants and industrial facilities to prevent the emission of new CO2, or remove older emissions, from polluting the atmosphere, while at the same time safely storing existing emissions into geological formations such as saline aquifers or depleted oil and gas reservoirs for permanent storage underground.
CO2 stream exiting CCS technologies must typically be compressed to supercritical state for transport and storage purposes; this incurs a significant energy penalty that adds significantly to overall costs of implementation.
CO2 is injected into rock formations like saline sandstone or basalt to be trapped between its pores, where it will remain safely contained within. Care is taken during injection so as to ensure no leakage back into the environment occurs; additionally it’s buried under an additional cap rock layer to further prevent surface migration – structural trapping being one of CCUS’ key elements.
Transportation
FECM projects establish networks to transport captured CO2 from power plants and industrial facilities (including legacy coal-fired power plants and direct air capture) to geologic formations where it can be safely and permanently stored underground. CO2 may also be utilized by manufacturing companies for creating fuels, chemicals, building materials or other long-lived products – known as utilization or CCUS – thus reducing emissions while still having climate benefits from permanent storage.
Even though pure carbon dioxide is non-corrosive, captured CO2 often contains impurities from combustion and other processes that may interact with other substances to form highly acidic acids that damage pipelines and tanks if stored incorrectly. Thus, its transportation infrastructure must be secure to ensure safe operations of CCUS facilities.
Storage
Once CO2 has been collected, it can be safely and permanently stored underground using geological storage technology. This involves injecting it under high pressure into a deep rock formation at high pressure while it’s in its supercritical state (dense like liquid but low viscosity like gas). There are various storage complexes including saline formations, depleted oil/natural gas reservoirs, unmineable coal areas and basalt formations as possible storage locations.
Before injection can take place, the subsurface must first be carefully evaluated. Rocks must be porous enough to accept carbon dioxide while having impermeable layers above for protection; additionally, storage sites must also be structurally sound.
Captured carbon dioxide has multiple uses, from building materials like concrete to oil recovery processes and as a water replacement in some chemical processes to use as biofuel. At present, however, such uses account for only a fraction of what would be required of CCUS capacity to meet climate goals.