Carbon dioxide in Earth's atmosphere initial carbon dioxide in the atmosphere of the young Earth was produced by volcanic activity, modern volcanic activity releases only 130 to 230 megatonnes of carbon dioxide each year. These natural sources are nearly balanced by natural sinks, physical and biological processes which remove carbon dioxide from the atmosphere. For example, some is directly removed from the atmosphere by land plants for photosynthesis and it is soluble in water forming carbonic acid. There is a large natural flux of into and out of the biosphere and oceans. In the pre-industrial era these fluxes were largely in balance. Currently about 57%
Ocean storage of carbon dioxide hydrate. Two regions are defined for exploration: the negative buoyancy zone (NBZ), which is the region between liquid carbon dioxide denser than surrounding water and where liquid carbon dioxide has neutral buoyancy, and hydrate formation zone (HFZ), which typically has low temperatures and high pressures. Several research models have shown that the optimal depth of injection requires consideration of intrinsic permeability and any changes in liquid carbon dioxide permeability for optimal storage. The formation of hydrates decreases liquid carbon dioxide permeability, and injection below HFZ is more energetically favored than within the HFZ. If the NBZ is a greater column