Biosequestration is the capture and storage of the atmospheric greenhouse gas carbon dioxide by biological processes.
This may be by increased photosynthesis (through practices such as reforestation / preventing deforestation and genetic engineering); by enhanced soil carbon trapping in agriculture; or by the use of algal bio sequestration (see algae bioreactor) to absorb the carbon dioxide emissions from coal, petroleum (oil) or natural gas-fired electricity generation.
Biosequestration as a natural process has occurred in the past, and was responsible for the formation of the extensive coal and oil deposits which are now being burned. It is a key policy concept in the climate change mitigation debate. It does not generally refer to the sequestering of carbon dioxide in oceans (see carbon sequestration and ocean acidification) or rock formations, depleted oil or gas reservoirs (see oil depletion and peak oil), deep saline aquifers, or deep coal seams (see coal mining) (for all see geosequestration) or through the use of industrial chemical carbon dioxide scrubbing.
After water vapour (concentrations of which humans have limited capacity to influence) carbon dioxide is the most abundant and stable greenhouse gas in the atmosphere (methane rapidly reacts to form water vapour and carbon dioxide). Atmospheric carbon dioxide has increased from about 280 ppm in 1750 to 383 ppm in 2007 and is increasing at an average rate of 2 ppm pr year. The world's oceans have previously played an important role in sequestering atmospheric carbon dioxide through solubility and the action of phytoplankton. This, and the likely adverse consequences for humans and the biosphere of associated global warming, increases the significance of investigating policy mechanisms for encouraging biosequestration.