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CO2 Sequestration
• Sequestration– To set off or apart; separate; segregate
• Why sequester CO2?
– Removal from atmosphere reduces the impact that anthropogenic CO2 emissions has on global warming.
Concerns with CO2
• Projections:– Population:
• 1950 - 2 billion• 2000 - 6 billion• 2050 - 10 billion
– Global Energy Consumption• 1950 - 15% based on electricity• 2050 - 70% based on electricity
– CO2 Emissions (in U.S.)• 32% generated from utilities (1995)
Sequestration by Conservation
• Carbon Dioxide Sinks– Forests (terrestrial sequestration via
photosynthesis)
• Carbon Dioxide Sources– Fossil fuel combustion– Deforestation
• Reallocation of agricultural land for residential uses
Non-carbon based energy
• Combustion based– Hydrogen as a fuel
• 2 H2 (g) + O2 (g) 2 H2O (g)
– Photoelectric
– Nuclear Power
• Costs:Time for research & development
Renewable Energy
• Solar
• Geothermal
• Hydroelectric
• Wind
• Ocean tides
• Cost:Altered ecology & biodiversity– Consider: Fossil fuels incur same costs
Iron Hypothesis• Seed oceans with ferrous ion (Fe2+)
– Phytoplankton growth kept in check due to iron deficiency (iron needed for synthesis of electron transport proteins and pigments)
– Iron promotes growth of phytoplankton
– Increase oceans’ ability to serve as CO2 sink
• Opposition over environmental tinkering– Excess growth may lead to decay of organisms
in absence of oxygen (forms methane - 21 times more powerful than CO2 as greenhouse gas)
http://www-personal.umich.edu/~rstey/Site%20files/science.html
REMOVAL OF CO2 BY BIOLOGICAL PUMP
• Phytoplankton would incorporate CO2 via photosynthesis
• Phytoplankton are consumed by other organisms and becomes part of organic carbon which sinks to ocean floor
Geological Sequestration
• Concentrate CO2 from emission sources
– Power plant CO2 emissions absorbed in
monoethanolamine (NH2CH2CH2OH)
– Thermally strip CO2 from absorbing solution
– Compress CO2 into a liquid
– Store in geological repositories• Depleted oil & gas reservoirs
• Porous strata (layers of sedimentary rock)
http://www.ornl.gov/ORNLReview/v33_2_00/research.htm
Carbon dioxide uptake by forests, biomass plantations, and degraded mine lands that are restored
Carbon-based products(e.g. fuels, power, wood, plastics)
Capture and Separation
Soil Amendments
Dispersed CO2
Geological Formations
Geological Sequestration
• Problems
– Costly to capture and separate CO2 ($65/ton)
– Difficult to predict CO2 movement underground
– Loss of CO2 to atmosphere???
Marine Sequestration
• Injection of liquefied CO2 deep into ocean
– Below 800 m (need high pressure)
• Ocean is good for CO2 sequestration
– Has large capacity for CO2
– Biological process may convert CO2 to organic
carbon compounds (such as alternative fuels)
http://www-esd.lbl.gov/DOCS/index2.html
Marine Sequestration
• Problems– Costly to separate and transport
– Local increase in acidity may be fatal to marine life
– Possible sudden release from oceans (blowouts)
Other Alternatives
• Sequestration of CO2 by converting
silicate based materials (quartz-bearing) to solid carbonates such as limestone (CaCO3) as an industrial process
• Creation of a biomimetic process– the enzyme carbonic anhydrase can
convert dissolved CO2 to solid carbonates,
analagous to marine life processes
– can be performed on-site (no transport!)