Carbon Sequestration Frequently Asked Questions
What is carbon sequestration?
Carbon sequestration is the capture and storage of carbon dioxide and other greenhouse gases that would otherwise be emitted to the atmosphere. Greenhouse gases can be captured at the point of emission or they can be removed from the air. The captured gases can be stored in underground reservoirs, dissolved in deep oceans, converted to rock-like solid materials, or absorbed by trees, grasses, soils, or algae.
What capture technology can be used at my local power plant?
In the future, emerging R&D will provide numerous cost effectives technologies for capturing carbon dioxide from power plants. At present, however, state-of-the-art technologies for existing power plants are essentially limited to “amine absorbents.” Such amines are used extensively in the petroleum refining and natural gas processing industries. The process works as follows. Flue gas that would normally go out the stack is bubbled through a solution of water and amines. The amines in the water react with the carbon dioxide in the flue gas to form an intermediate chemical called a rich amine. The rich amine is soluble and stays in the water solution. Some of the flue gas bubbles out of the top of the amine solution and is emitted to the air just like the flue gas was before, but a portion of the carbon dioxide has reacted with the amines and remains in solution. The rich amines are pumped to another vessel where they are heated to make them decompose back into regular (lean) amines and carbon dioxide gas. The pure carbon dioxide gas is collected from this vessel and the regular amines are recycled to the flue contactor gas vessel.
Once you capture the carbon dioxide from a power plant, what can you do with it?
Generally speaking there are three possibilities: (1) Use the carbon dioxide as a value added commodity; (2) store the carbon dioxide, such as in underground formations; or (3) convert the carbon dioxide to methane, biomass, mineral carbonates, or other substances. Some of the uses for commodity carbon dioxide result in a portion of the carbon dioxide being sequestered, a double benefit. Most notable among these is enhanced oil recovery. Oil companies currently inject over 30 million tons of carbon dioxide per year in depleting oil formations to enhance the production of crude oil. A portion of this carbon dioxide remains underground. A similar carbon dioxide use/storage application is in the enhancing of methane production from coal seams that are too deep to be mined. Concepts for converting carbon dioxide to other chemicals, especially fuels, are in the very early stages of research.
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