Carbon Sequestration - One of two student blogs

Carbon Capture

Dr. Watson
Earth and Environmental Science

1/22

For millennia, the earth  atmospheric  carbon has naturally cycled from 180 to 280 ppm. Right now it is beyond 380 ppm.  Carbon dioxide is 84.8 percent of all emissions.  We release so much that we measure it in teragrams. (10 to the 12th power)  Natural sources of carbon dioxide are forest fires and volcanoes. Other sources include fossil fuels, non-energy fuel use, iron and steel production, cement manufacture, natural gas systems, municipal solid waste consumption, petroleum, coal, etc. Electricity generation works mainly with coal, while petroleum is used for transportation and is used the most.  These are isotopically different than fossil fuels, so we can tell the source of carbon in the atmosphere.

Carbon Dioxide can be  captured by pulling it out of the atmosphere. This is not currently regarded as practical or economical CO2 can be captured or reduced by power plants and industrial facilities at the “point source”. Three approaches to do so are post-combustion capture, pre-combustion capture, and oxy-fuel combustion capture. Once captured, pure carbon dioxide can be stored geologically, in oceans, or through mineralization.

Terms:

• Geologic storage: place carbon dioxide into empty oil and gas wells
• Ocean storage: Large capacity to absorb carbon dioxide, but changes pH of ocean
• Mineral carbonation: make solid carbonates by essentially reversing the process used to make cement. CaO (lime) or MgO + CO2 à CaCO3 or MgCO3 + heat.  This is exothermic, so once started, the reaction should continue, but it’s hard to drive the reaction to completion.  Researchers are working to make this process efficient and successful.
• Post-combustion capture: waste gas is scrubbed of carbon dioxide
• Pre-combustion capture: fossil fuels oxidized in gasifier, take CO2 out and then burn the fuel in hydrogen. This is complex chemistry and currently expensive
• Oxy-fuel combustion capture: burned with oxygen rather than air so that the waste stream is pure CO2  which is easier to capture and store.
• Carbon carousel: a device with fiber mats that rotae and pull CO2 out of the air, making bicarbonate. The bicarbonate can then be made into a solid as benign as sodium bicarbonate.  Right now this is just a prototype.
• Sequestration:

Connections:

Katz- climate change

Ji- nuclear energy

Borton- solar energy