Using seawater doped with sodium bicarbonate and Celgard 2400 gas permeable membranes, bicarbonate ion disproportionates to carbon dioxide and carbonate when gaseous carbon dioxide is first removed from the seawater Solution by diffusion through gas permeable membranes at elevated water pressures. The permeability of CO2 by phase transition from bicarbonate Solutions at pressures above 100 psi is only possible due to the use of mulitple gas permeable membrane layers. The multiple layers minimize water permeability at pressures below and above the Young-Laplace bubble point of single membrane layers, however the gas permeability efficiency and rate are greatly decreased.