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
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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)
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
http://www-personal.umich.edu/~rstey/Site%20files/science.html
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)
Dispersed CO2
Carbon dioxide uptake by forests, biomass plantations,
and degraded mine lands that are restored
Capture and
Separation
Carbon-based
products(e.g. fuels,
power, wood, plastics)
Soil
Amendments
Geological
Formations
http://www.ornl.gov/ORNLReview/v33_2_00/research.htm
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!)