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Carbon capture, use and storage (CCUS) is an integrated suite of technologies that can capture up to 90% of the CO2 emissions produced from the use of fossil fuels in electricity generation and industrial processes, preventing the CO2 from entering the atmosphere.
Capture technologies allow the separation of CO2 from gases produced in electricity generation and industrial processes by one of three methods:
- Pre-combustion capture
- Post-combustion capture
- Oxyfuel combustion
CO2 is then transported for safe use or storage. Millions of tonnes of CO2 are already transported annually for commercial purposes by pipelines, ships and road tanker. The US has four decades of experience of transporting CO2 by pipeline for enhanced oil recovery projects.
Use and storage
CO2 can be used as a value-added commodity. This can result in a portion of the CO2 being permanently stored – for example, in concrete that has been cured using CO2 or in plastic materials derived from biomass that uses CO2 as one of the ingredients. The CO2 can also be converted into biomass. This can be achieved, for example, through algae farming using CO2 as a feedstock. The harvested algae can then be processed into bio-fuels that take the place of non-biological carbon sources.
Enhanced oil recovery
CO2 is already widely used in the oil industry for enhanced oil recovery (EOR) from mature oilfields. When CO2 is injected into an oilfield it can mix with the crude oil causing it to swell and thereby reducing its viscosity, helping to maintain or increase the pressure in the reservoir. The combination of these processes allows more of the crude oil to flow to the production wells. In other situations, the CO2 is not soluble in the oil. Here, injection of CO2 raises the pressure in the reservoir, helping to sweep the oil towards the production well. In EOR, the CO2 can therefore have a positive commercial value and can help support the deployment of CCUS and create a revenue stream for CCS projects, as the CO2 captured becomes an economic resource.
CO2 is stored in carefully selected geological rock formations that are typically located several kilometres below the earth’s surface. As CO2 is pumped deep underground, it is compressed by the higher pressures and becomes essentially a liquid. There are a number of different types of geological trapping mechanisms (depending on the physical and chemical characteristics of the rocks and fluids) that can be utilised for CO2 storage.
At every point in the CCUS chain, from production to storage, industry has at its disposal a number of process technologies that are well understood and have excellent health and safety records. The commercial deployment of CCUS will involve the widespread adoption of these CCUS techniques, combined with robust monitoring techniques and government regulation.
Posted by: The Global Compost Project
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