Carbon Capture and Storage (CCS) reduces greenhouse gases by collecting them at factories or fossil fuel-burning power plants and transporting it to sites where its benefits can be utilized or stored permanently underground in porous rock formations.
Injection sites tend to be depleted oil and gas fields or deep saline aquifers. Basalt formations also have potential storage solutions through mineralization that would permanently trap CO2.
How CCS Works
Capturing carbon dioxide emissions from industrial processes and storing it underground permanently offers an effective means to lower greenhouse gas emissions while still producing energy. CCS technology is currently employed in industries with low costs for CO2 capture such as natural gas processing or ammonia or ethanol production.
Flue gases produced from these processes must pass through a solution of special chemicals called amines to capture CO2. The amines bind with CO2, leaving all other gases free to pass unimpeded.
CO2 can be transported long distances by pipeline or ship and stored at storage sites across long distances. Many types of geologic formations offer potential storage sites; the most promising in the US are deep saline aquifers which contain massive expanses of porous rock that hold salt water underground.
Regulation decisions at both state and federal levels will have a substantial effect on CCS technology’s future development. For instance, new rules limiting emissions from power plants could make CCS technology more appealing.
Capture
Carbon Capture refers to the process of collecting CO2 emissions from industrial processes such as power plants or steel and cement factories and then permanently storing it underground.
CCS can be applied to different sources of energy, from fossil fuels like coal and natural gas, as well as renewable sources like solar. Multiple capture technologies exist or are under development depending on your emissions source.
Some of these methods include post-combustion (separating CO2 from flue gases of fossil fuel plants), while others use oxyfuel technology, in which fossil fuel is burned with pure oxygen instead of air to increase carbon-dioxide concentration in its exhaust gasses.
Once captured, captured CO2 can be compressed into liquid form and sent through pipelines for storage in depleted oil and gas fields or deep geologic formations. There are currently more than 4,500 miles of CO2 transportation pipelines across the US for enhanced oil recovery applications.
Transport
Once carbon dioxide has been collected, it must be transported to an appropriate storage site – typically via pipelines already established to transport natural gas across the world.
Pipelines transport gas by increasing pressure inside them and pressurizing their contents, increasing density while simultaneously decreasing viscosity, making the substance behave more like liquid than gas. Before CO2 can be transported this way it must first be dehydrated so as not to react with other chemicals in the pipeline or cause corrosion issues.
Compressing CO2 reduces its volume significantly and is particularly helpful when transporting large volumes over long distances. Once compressed, CO2 can then be put into ships or road tanker trucks and delivered directly to its storage site, where it will eventually be safely and permanently stored within underground rock formations.
Storage
A key challenge of carbon capture and storage (CCUS) lies in how it stores captured carbon permanently; one solution could be transporting it deep underground via geological formations such as old oil and gas wells.
CO2 is compressed to liquid-like state before being transported by pipeline or ship (depending on local conditions) to its storage site, where it will then be injected deep below earth’s surface into rocks in an impermeable layer of cap rock, where it will become trapped over time; this process is known as structural trapping.
CCUS technology differs significantly from natural carbon sinks, which store carbon through decomposition or reentry into the atmosphere through erosion or forest fires, in that human-produced CO2 can be stored geologically for centuries or millennia compared to these processes.