Some have argued that because the ocean is the largest carbon reservoir on Earth, holding significantly more carbon than the atmosphere or terrestrial biosphere, deep sea mining would release carbon.
However, the reality is that less than 1% of the CO2 sequestered in the ocean’s upper layers reaches the deep sea floor annually. As the carbon-based organic matter sinks to the bottom of the ocean, much of it is processed before reaching the ocean floor. Due to lower productivity and reduced input of organic matter, deep-sea sediments have an overall low organic carbon content of approximately 0.05% of the dry weight of the sediment. Nodules do not sequester CO2 and do not contain a meaningful amount of carbon. Sediment disturbed by the collector vehicle has no pathway to the atmosphere. Local sediment disturbance has shown not to rise more than a few meters, many meters away from phytoplankton, which need light for photosynthesis. Impossible Metals has no riser system with a mid-column discharge plume, so this will not impact phytoplankton photosynthesis.
Any possible carbon sink impacts will be confirmed by scientists as part of the Environmental Impact Assessment (EIA) before permission is granted to start mining. See more details in the ISA Fact-check 2024/1 – The carbon cycle in the Area.
