Carbon Capture, Utilization, and Storage

What is CCUS?

Carbon capture, utilization and storage (CCUS) is a process of sequestrating and recycling CO2 from emission sources and the atmosphere. CO2 is a major contributor to global warming and climate change. CCUS is just one of the many geoengineering ideas scientists are considering today. There are four stages in CCUS: capture, transport utlization and storage of carbon dioxide. Our research focuses on capturing CO2.

 

Capture Removal of carbon from the point source is the first step in CCS. An example of a point source is flue gas emitted from industrial plants. Capturing CO2 when it is in a concentrated stream is much easier than a dilute one; however, modern technology has enabled us to remove CO2 that is already in the atmosphere (the different capturing methods are described below). Industrial facilities are becoming more environmentally aware and are integrating carbon capture  technology within their operations.
Transport Carbon dioxide is compressed (turned into liquid form) and transported to storage sites via pipelines, ship or truck. Pipeline transport is the dominant method of transport but other methods may be chosen as seen appropriate with respect to health and safety.
Utilization This stage aims to make the most of this captured COby looking at opportunities like conversion into useful chemicals, enhanced oil recovery (EOR), recovering untapped oil, or alkaline remediation. This is done by taking the combustion exhaust stream as raw material.
Storage Carbon dioxide is permanently stored underground by injecting it into rock formations several kilometers below the surface. This process is called geosequestration. The storage sites are chosen based on the vast amount of porous rocks they have underground. The CO2 injected will fill the pores between these rocks and is kept there by an impermeable layer covering it from above. This process is almost identical to how oil and gas is naturally stored underground.

Process diagram for CO2 reactive absorption


What are the different capture methods?

Pre-Combustion Carbon dioxide is captured and removed before fuel combustion.
Post-Combustion Currently the most popular capture technology in CCUS. The CO2 is removed from the flue gas after a combustion process, for example from a coal-fired power plant, a cement plant, or a steel manufacturing plant.
Post-Production This is similar to Post-Combustion, but occurs when a desired product (e.g., H2 or ethanol) is produced, and the product stream contains CO2, which must be removed.
Oxy-Fuel Combustion Similar to the post-combustion process except the fuel is combusted in oxygen instead of air. This causes the flue gas to be more concentrated in CO2 which facilitates the purification process
DIrect Air Capture Unlike the other CCUS capturing methods, Direct Air Capture (DAC) does not require high concentrations of carbon dioxide to work. Simply put, DAC is like creating an artificial plant that is much more efficient at removing CO2 from the surrounding air than real plants.