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)
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)
Carbon dioxide uptake by forests, biomass plantations, and degraded mine lands that are restored Dispersed CO2 Carbon-based products(e.g. fuels, power, wood, plastics) Capture and Separation 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)
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!)