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

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. 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. 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. 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. 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. 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. 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. 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. 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. 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-