A CO2 scrubber is equipment or a machine that takes air in, absorbs carbon dioxide and releases clean air without carbon dioxide back into the local environment. CO2 scrubbers are essential for cleaning the air in submarines and spacecraft, but with the threat of global warning, the technology is also needed to reduce carbon dioxide emissions from coal-fired power plants. Using CO2 scrubbers to remove carbon dioxide from the atmosphere is controversial and awaits improvements in technology.
Carbon Dioxide Capture
Air is drawn into the CO2 scrubber at a relatively low temperature and is bound chemically to an absorber or solvent. About 90 percent of the carbon dioxide chemically binds to the absorber and the remaining air is released. The efficiency of carbon dioxide capture depends on the surface area of the absorber, with liquid mists being highly efficient. After carbon capture, the carbon dioxide-loaded liquid absorber is heated to release carbon dioxide for transport or storage. The absorber is then recycled to capture more carbon dioxide. However, absorber recycling is not forever -- at some point the absorber has to be replaced.
Storing and Using Removed Carbon Dioxide
The carbon dioxide captured by a CO2 scrubber is of great purity and after compression can be transported to an underground storage facility or an industrial site that needs carbon dioxide, such as an algae biofuel plant. Other potential industrial uses of captured carbon dioxide are in food processing, fire extinguishers and for plant growth in greenhouses. Some proposed uses, such as the synthesis of hydrocarbon fuel from carbon dioxide and hydrogen, are still on the drawing board.
CO2 Scrubbers for Coal-Fired Power Plants
Coal-fired power plants are a major source of carbon dioxide emissions globally and in the United States. About 2.8 billion tons of carbon dioxide from 8,000 coal-fired power plants in the United States alone enter the atmosphere yearly, according to the American Chemical Society. Chemicals used in CO2 scrubbers for capturing carbon dioxide are currently not efficient enough to be cost effective. However, developing new carbon dioxide capture technologies are promising to be more efficient and cheaper.
CO2 Scrubbers for the Atmosphere
Using large scale CO2 scrubbers to remove carbon dioxide from the air to prevent global warming is theoretically feasible, but analyses show that carbon capture with present day technology would be too costly. While the exhaust air from coal-fired power plants contains 10 percent carbon dioxide, carbon dioxide in the atmosphere constitutes only 0.04 percent. The large CO2 scrubbers would need too much energy to heat the absorber and to process the carbon dioxide.
- The Economist: Scrubbing the Skies
- RWE: CO2 scrubbing Process Overview
- American Chemical Society: New CO2 "Scrubber" from Ingredient in Hair Conditioners
- Midwest Energy News: Ohio State's Carbon-Capture Breakthrough Still Has Long Road to Adoption
- Proceedings of the National Academy of Sciences: Economic and Energetic Analysis of Capturing CO2 from the Ambient Air
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