Carbon Sequestration
Ways to Store CO2
Rocks
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Carbon Sequestration Overview
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To put it simply, underground rock formations or structures with the right characteristics can be used to store carbon dioxide (CO2). This is called geologic sequestration. Many of these structures have already been storing carbon dioxide for millions of years.
For many years, CO2 has been injected into underground oil and gas formations because CO2 can push the oil and gas to the surface. The oil and gas industries use CO2 for this enhanced recovery as a standard business practice.
In the United States, enhanced oil recovery (EOR) operations inject up to 30 MtCO2 yr, according to the Intergovernmental Panel on Climate Change Special Report on Carbon Dioxide Capture and Storage At the Weyburn Project in Canada 1–2 MtCO2 are currently injected annually. The project combines EOR with a comprehensive monitoring and modeling to evaluate CO2 storage.
There are many options for geologic storage, including: depleted or depleting oil and gas formations, deep unmineable coal seams, and deep saline formations (layers of porous rock that are saturated with brine). In general, porous rocks surrounded by impermeable rock are ideal CO2 storage sites. Most reservoir rocks consist of limestone, dolomites, or sandstone. Research in this area seeks to understand the behavior of CO2 when stored in geologic formations and ensure that the storage is environmentally acceptable and secure.
Trees
Trees, shrubs, plants, grass, and even flowers are also storage sites for carbon. This is called terrestrial sequestration. As a part of the natural carbon cycle, carbon is stored in plants’ tissue above-ground and below-ground in the roots. In 2006, about 110 gigatons per year of carbon was absorbed by the atmosphere into plant life through the process of photosynthesis, according to the Center for Terrestrial Ecosystem Carbon. The United States has many acres of farmland and forests that naturally store carbon. Early terrestrial sequestration efforts include tree plantings, no-till farming, and forest preservation. More advanced research includes developing fast-growing trees and grasses, deciphering the genomes of carbon-storing soil microbes, amending mine lands and other damaged soils, analyzing various land management techniques, reforestation, rangeland improvement, wetlands recovery, and riparian restoration.
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Currently, terrestrial uptake offsets roughly 1/3 of global anthropogenic CO2 emissions. The uptake from domestic terrestrial ecosystems is expected to decrease 13% over the next 20 years unless forest lands are replenished. Other opportunities for enhanced terrestrial sequestration include 1.5 MM acres of land damaged by past mining practices, 32 MM acres of CRP farmland, and 120 MM acres of pastureland. |
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