Skip to main content.
Enviropaedia Sponsors and Supporters

Carbon storage/ Sequestration

Author: Robyn Ferrar - Living Wealth

( Article Type: Explanation )

Carbon sequestration is the process by which carbon is removed (naturally or artificially) from the atmosphere and effectively placed in storage. The field has received a lot of attention recently due to its potential for mitigating or deferring climate change.
Most atmospheric carbon is derived from the breakdown of biological tissue, mainly plants and micro-organisms.
Biosequestration is essentially a component of photosynthesis, or nature’s age-old ability to absorb atmospheric carbon dioxide and convert it into organic compounds, with oxygen produced as a waste product. The net effect is that carbon is locked away in the soil or biomass where it cannot contribute to anthropogenic global warming. Certain types of plants are more efficient or more desirable for the purposes of bio-sequestration, than others. Spekboom, a large shrub indigenous to South Africa, has recently been shown to sequester comparatively large amounts of carbon for its class (~0.42kg C/m2/yr).
Although the rate of sequestration is comparable to many temperate and tropical forest plants, this semi-arid succulent shrub is water-wise, easily propagated and beneficial to the biodiversity of its native region. Ocean iron fertilization, a method of artificially enhancing the natural process of carbon sequestration, involves the intentional introduction of iron to the iron-scarce regions of the ocean to stimulate a phytoplankton bloom. Plankton generate calcium or silica carbonate skeletons and when the organisms die, their skeletons sink and form a major component of the carbon-rich deep sea precipitation known as marine snow, contributing to carbonate rich sediments and eventually rocks.
Twenty to thirty percent of the carbon rich biomass generated sinks below 200 meters into the coldwater strata, some of which settles as sediment on the ocean floor where it is finally isolated. However, experiments have shown that sustained high concentrations of CO2 in the ocean would lead to ocean acidification, which would be detrimental to marine life and eventually contribute to increased CO2 levels in the atmosphere.

Artificial methods of carbon sequestration are numerous, and all amount to geo-engineering. This is essentially the deliberate manipulation of the Earth’s environment in order to counteract the effects of global warming. Geosequestration is the process of capturing and injecting carbon dioxide directly into underground geological formations in a way that does not allow it to escape back to the surface. Trials have been carried out in various locations and formations worldwide, including mined oil fields where results have shown an improvement in the quality of the oil yield.
These artificial methods, especially the bolder ones such as geo-sequestration, have raised fundamental ethical concerns regarding the continued manipulation of the natural environment, as well as fears of the unintended, long-term knock-on effects. Other concerns exist around the transportation, storage and leakage of CO2, as well as the potential for accidents.
Clarification is also required as to the energy cost of such practices and whether this has been offset against potential benefits. Constant monitoring of CO2 reserves will be required and the cost and responsibility of such monitoring will be ongoing forever, and some argue that carbon cannot be considered sequestered if it depends on human agency. These issues remain the subject of much debate whilst projects, trials and experiments forge ahead worldwide.

Associated Topics:

Afforestation , Biomass , Eco-taxes , Kyoto Protocol , Carbon