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Sequestering carbon dioxide from the atmosphere by enhancing the capacity of the oceans to act as a carbon sink Tim Kruger...
CaCO 3     CaO + CO 2 Thermally decompose (calcine) limestone at temperatures greater than 850C Δ H = +163kJ/mol * Assumi...
CaCO 3     CaO + CO 2 CaO + H 2 O    Ca(OH) 2 Ca(OH) 2  + 2CO 2     Ca(HCO 3 ) 2 Concept The calcium oxide generated fr...
CaCO 3     CaO + CO 2 CaO + H 2 O    Ca(OH) 2 Ca(OH) 2  + 2CO 2     Ca(HCO 3 ) 2 CO 2  + H 2 O  H 2 CO 3   H +  + HCO 3...
CaCO 3     CaO + CO 2 CaO + H 2 O    Ca(OH) 2 Options Ca(OH) 2  + 2CO 2     Ca(HCO 3 ) 2 CO 2  + H 2 O  H 2 CO 3   H + ...
CaCO 3     CaO + CO 2 CaO + H 2 O    Ca(OH) 2 Options Release Ca(OH) 2  + 2CO 2     Ca(HCO 3 ) 2 CO 2  + H 2 O  H 2 CO ...
CaCO 3     CaO + CO 2 CaO + H 2 O    Ca(OH) 2 Options Release Sequester Ca(OH) 2  + 2CO 2     Ca(HCO 3 ) 2 CO 2  + H 2 ...
CaCO 3     CaO + CO 2 CaO + H 2 O    Ca(OH) 2 Options Release Sequester Fuel Production Ca(OH) 2  + 2CO 2     Ca(HCO 3 ...
CaCO 3     CaO + CO 2 CaO + H 2 O    Ca(OH) 2 Options Release Sequester Fuel Production Reduce to Carbon Ca(OH) 2  + 2CO...
Concept CaCO 3     CaO + CO 2 CaO + H 2 O    Ca(OH) 2 Options Release Sequester Fuel Production Reduce to Carbon Growing...
Growing biomass in arid environments <ul><li>Little biomass  is generated in  arid environments  because there is  insuffi...
Burning methane to calcine limestone leads to a net reduction in carbon dioxide <ul><li>Energy required to drive calcinati...
Potential sources of energy <ul><li>Stranded gas </li></ul><ul><li>Solar irradiation </li></ul><ul><li>Geothermal heat </l...
Where this could be done <ul><li>The Nullarbor Plain is  the world's largest single piece of limestone, and occupies an ar...
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Cquestrate Presentation

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A presentation detailing the basis of the Cquestrate project and outlining the possible benefits.

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Cquestrate Presentation

  1. 1. Sequestering carbon dioxide from the atmosphere by enhancing the capacity of the oceans to act as a carbon sink Tim Kruger www.cquestrate.com
  2. 2. CaCO 3  CaO + CO 2 Thermally decompose (calcine) limestone at temperatures greater than 850C Δ H = +163kJ/mol * Assuming no recapture of heat, energy requirement is 2.669GJ/tonne of CaCO 3 * Reaction enthalpy calculated at 1000C Concept
  3. 3. CaCO 3  CaO + CO 2 CaO + H 2 O  Ca(OH) 2 Ca(OH) 2 + 2CO 2  Ca(HCO 3 ) 2 Concept The calcium oxide generated from the calcination of limestone is added to seawater At seawater pH, the calcium oxide will form a solution of calcium bicarbonate For each mol of CO 2 emitted during the calcination, almost two mols of CO 2 will be absorbed in the seawater Δ H = -65kJ/mol
  4. 4. CaCO 3  CaO + CO 2 CaO + H 2 O  Ca(OH) 2 Ca(OH) 2 + 2CO 2  Ca(HCO 3 ) 2 CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - 2H + + CO 3 2- Concept On addition of calcium oxide to seawater, the system of equilibria associated with the dissolution of CO 2 in water will be shifted to the right. This increases the capacity of the oceans to act as a carbon sink , whilst simultaneously mitigating the effects of ocean acidification caused by heightened levels of CO 2 in the atmosphere
  5. 5. CaCO 3  CaO + CO 2 CaO + H 2 O  Ca(OH) 2 Options Ca(OH) 2 + 2CO 2  Ca(HCO 3 ) 2 CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - 2H + + CO 3 2- Concept There are five potential ways in which to deal with the pure CO 2 produced in the calcination process
  6. 6. CaCO 3  CaO + CO 2 CaO + H 2 O  Ca(OH) 2 Options Release Ca(OH) 2 + 2CO 2  Ca(HCO 3 ) 2 CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - 2H + + CO 3 2- Concept Releasing CO 2 into the atmosphere may seem counterproductive – we are after all trying to remove CO 2 – but given that the process is net ‘carbon negative’ even if the CO 2 emitted is released, this may be the most economic route
  7. 7. CaCO 3  CaO + CO 2 CaO + H 2 O  Ca(OH) 2 Options Release Sequester Ca(OH) 2 + 2CO 2  Ca(HCO 3 ) 2 CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - 2H + + CO 3 2- Concept The cost for geologically storing pure CO 2 has been estimated to be USD0.5 – 8 per tonne of CO 2 . In comparison sequestering carbon dioxide from the flue gases of a conventional fossil fuel power plant, where the CO 2 concentration is typically in the region of 10% , costs in the region of USD47 per tonne of CO 2
  8. 8. CaCO 3  CaO + CO 2 CaO + H 2 O  Ca(OH) 2 Options Release Sequester Fuel Production Ca(OH) 2 + 2CO 2  Ca(HCO 3 ) 2 CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - 2H + + CO 3 2- Concept With the addition of more energy , pure CO 2 can be used as a feedstock for the production of hydrocarbons
  9. 9. CaCO 3  CaO + CO 2 CaO + H 2 O  Ca(OH) 2 Options Release Sequester Fuel Production Reduce to Carbon Ca(OH) 2 + 2CO 2  Ca(HCO 3 ) 2 CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - 2H + + CO 3 2- Concept With the addition of more energy, pure CO 2 can be reduced to carbon. If CO 2 emissions are no longer a problem, carbon is an excellent energy vector , with 6000 times the energy per unit volume of unpressurised hydrogen
  10. 10. Concept CaCO 3  CaO + CO 2 CaO + H 2 O  Ca(OH) 2 Options Release Sequester Fuel Production Reduce to Carbon Growing Biomass in Arid Environments Ca(OH) 2 + 2CO 2  Ca(HCO 3 ) 2 CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - 2H + + CO 3 2-
  11. 11. Growing biomass in arid environments <ul><li>Little biomass is generated in arid environments because there is insufficient water </li></ul><ul><li>One way of growing biomass in an arid environment is to stop water escaping by using a sealed greenhouse </li></ul><ul><li>Unfortunately, when plants grow they rapidly use up the available carbon dioxide in the greenhouse. If you change the air to allow more carbon dioxide to enter the system, you lose moisture </li></ul><ul><li>Alternatively, have a sealed tank of water with algae in it and into it add pure carbon dioxide . You have everything you need for photosynthesis. </li></ul><ul><li>Water requirements to produce biomass are reduced a thousand-fold in comparison to conventional irrigation techniques </li></ul><ul><li>This reduced water requirement allows for biomass production in even the most arid environments without the need for irrigation </li></ul>
  12. 12. Burning methane to calcine limestone leads to a net reduction in carbon dioxide <ul><li>Energy required to drive calcination of limestone: 2.669GJ/tonne of CaCO 3 </li></ul><ul><li>The released carbon dioxide can be used for preheating the limestone feed, lowering the external heat requirements to 2.244GJ/tonne of CaCO 3 </li></ul><ul><li>The enthalpy change of reaction of calcium oxide with water to yield calcium hydroxide is -65kJ/mol. This could further reduce the external heat energy requirements </li></ul><ul><li>The combustion of methane is an exothermic reaction with an enthalpy change of 890kJ/mol at stp. The combustion of 0.3mols of methane provides sufficient heat energy to calcine one mol of CaCO 3 </li></ul><ul><li>Thus 1.3mols of CO 2 are generated and 1.8mols are captured, a net sequestration of 0.5mols . If the CO 2 generated from the calcination is sequestered a net 1.5mols of CO 2 will be sequestered </li></ul>
  13. 13. Potential sources of energy <ul><li>Stranded gas </li></ul><ul><li>Solar irradiation </li></ul><ul><li>Geothermal heat </li></ul><ul><li>Biomass </li></ul><ul><li>Nuclear processes </li></ul>
  14. 14. Where this could be done <ul><li>The Nullarbor Plain is the world's largest single piece of limestone, and occupies an area of about 200,000 km² </li></ul><ul><li>With an average thickness of 50m, there is 10,000km 3 of limestone </li></ul><ul><li>To sequester 1 billion tonnes of carbon (GtC) would require the excavation of 1.5km 3 of limestone </li></ul><ul><li>Between 1750 and 2003 humankind has emitted 305 GtC. Current emission rates are about 7 GtC per year. </li></ul><ul><li>Thus employing this process on 500km 3 of limestone (about 5% of the limestone in the Nullarbor Plain) would return carbon dioxide levels to pre-industrial levels </li></ul>

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