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!)