Greenhouse gas emissions are the fundamental cause of Global warming. Greenhouse gases form a blanket-like structure in the atmosphere that prevents the escape of heat radiated on the earth, trapping the heat in the earth’s atmosphere and resulting in global warming. However, of all the greenhouse gases, Carbon dioxide remains in the atmosphere for an estimated 300 to 1000 years. This contributes to global emissions. Carbon is a composite of fossil fuels burned globally, from coal to crude, and is released into the atmosphere by various sectors. Carbon capture, use and storage technology is one of the technologies utilised in offsetting carbon emissions in the atmosphere. Industrial and power plants’ Carbon Capture Utilization and Storage (CCUS) technologies can effectively capture about 90 percent of CO2 emitted from the processes. Also, According to the IEA report, CCUS will account for about 15% of the cumulative emissions reduction needed by 2070.
CCUS entails capturing CO2 in concentrated streams from the atmosphere, industries, and power generation sources that utilise fossil or biomass fuels. The captured CO2 can be compressed for transportation, used on-site or stored underground. The captured CO2 can be used in enhancing oil recovery, in fertiliser production, in the production of building materials, as an additive to convert hydrogen to synthetic hydrocarbon fuel, for water treatment, etc. According to IEA reports, CCUS accounted for 44MT of CO2 in 2021. CCUS is used in areas where the generation of CO2 cannot be avoided.
Carbon storage is one of the ways of offsetting environmental carbon. It involves injecting the CO2 captured into porous rocks’ geological reservoirs underground; these rocks are overlaid by an impermeable rock that prevents the leakage of CO2 into the atmosphere by sealing the reservoir. The injected CO2 flows through the reservoir, usually at depths below 800 meters, filling the pore spaces. The reservoirs then retain the CO2 in dense liquid forms. There are two approaches to CCUS; Firstly, Direct Air Capture (DAC) involves capturing CO2 from ambient air. Carbon captured through this technique can be used as feedstock in synthetic fuels or permanently stored for carbon removal. Secondly, Bioenergy with Carbon Capture And Storage(BECCS) is a technology deployed in power stations fueled by biomass or in the conversion process of biomass to biofuels.
A brief highlight of CCUS project sites around the world:
- Boundary Dam carbon capture and storage: The first project capturing and storing CO2 from a coal-fired power plant at a commercial scale. It is located in Saskatchewan, Canada.
- Air Products steam methane reformer: This facility is located within the Valero Port Arthur refinery, Texas, US. It had CO2 capture units retrofitted in 2013. The CO2 is transported by pipeline for about 158Km to drive EOR
- Snøhvit CO2 Storage facilities: This is an offshore facility located in Norway. Here, Natural gas containing 5-6% CO2 is piped to shore from subsea production facilities to the Melkoya gas processing facility near Hammerfest. The CO2 is separated using amine capture and directed back to the Snohvit, where it is injected into the saline aquifer.
- Qatar LNG carbon capture and storage: This involves capturing CO2 from a Qatar gas liquified natural gas (LNG) facility. The CO2 captured is then used for enhanced oil recovery.
- Jilin oilfield CO2-EOR: This involves capturing CO2 from a natural gas processing plant at the Changling gas field. The CO2 is transported over 53km by pipeline and is injected into low permeability reservoirs of the Jilin oil field in northeast China for EOR.
With about 26 commercial CCUS projects and 34 undergoing construction, the use and storage of carbon can make an impact in reducing greenhouse carbon emissions around the world in areas where its use of fossil or heavy carbon-emitting fuels cannot be completely avoided. Like little drops of water that make a mighty ocean, fighting the global climate crisis will be won by taking different initiatives such as this.