![Carbon cycle](https://upload.wikimedia.org/wikipedia/commons/d/d5/Carbon_cycle.jpg)
A carbon sink is anything, natural or otherwise, that accumulates and stores some
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
-containing
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
for an indefinite period and thereby removes
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
() from the atmosphere.
Globally, the two most important carbon sinks are
vegetation
Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characte ...
and the
ocean
The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...
. Public awareness of the significance of sinks has grown since passage of the 1997
Kyoto Protocol, which promotes their use as a form of
carbon offset
A carbon offset is a reduction or removal of emissions of carbon dioxide or other greenhouse gases made in order to compensate for emissions made elsewhere. Offsets are measured in tonnes of carbon dioxide-equivalent (CO2e). One ton of carb ...
. There are also different strategies used to enhance this process. Soil is an important carbon storage medium. Much of the organic carbon retained in the soil of agricultural areas has been depleted due to
intensive farming
Intensive agriculture, also known as intensive farming (as opposed to extensive farming), conventional, or industrial agriculture, is a type of agriculture, both of crop plants and of animals, with higher levels of input and output per unit of ...
. "
Blue carbon" designates carbon that is fixed via the ocean ecosystems.
Mangrove
A mangrove is a shrub or tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in severa ...
s,
salt marsh
A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is domin ...
es and
seagrass
Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the or ...
es make up a majority of ocean plant life and store large quantities of carbon.
Many efforts are being made to enhance natural sequestration in soils and the oceans.
In addition, a range of artificial sequestration initiatives are underway such as changed building construction materials,
carbon capture and storage
Carbon capture and storage (CCS) or carbon capture and sequestration is the process of capturing carbon dioxide (CO2) before it enters the atmosphere, transporting it, and storing it (carbon sequestration) for centuries or millennia. Usually th ...
and geological sequestration.
General
![CO2 pump hg](https://upload.wikimedia.org/wikipedia/commons/f/fb/CO2_pump_hg.svg)
Increase in atmospheric
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
means increase in global temperature. The amount of carbon dioxide varies naturally in a dynamic equilibrium with photosynthesis of land plants. The natural sinks are:
*
Soil
Soil, also commonly referred to as earth or dirt
Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty.
Common types of dirt include:
* Debri ...
is a carbon store and active carbon sink.
*
Photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
by terrestrial plants with grass and trees allows them to serve as carbon sinks during growing seasons.
* Absorption of carbon dioxide by the oceans via
solubility
In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution.
The extent of the solub ...
and
biological pumps
While the creation of artificial sinks has been discussed, no major artificial systems
remove carbon from the atmosphere on a material scale yet.
Carbon sources include the combustion of fossil fuels (coal, natural gas, and oil) by humans for energy and transportation.
Kyoto Protocol
The Kyoto Protocol was an international agreement that aimed at reducing carbon dioxide () emissions and the presence of greenhouse gases (GHG) in the atmosphere. The essential tenet of the Kyoto Protocol was that industrialized nations needed to reduce their emissions.
Because growing vegetation takes in
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
, the
Kyoto Protocol allows
Annex I countries with large areas of growing forests to issue
Removal Units
A Removal Unit (RMU) is a tradable carbon credit or 'Kyoto unit' representing an allowance to emit one tonne of greenhouse gases absorbed by a removal or carbon sink activity in an Annex I country.
Removal Units are generated and issued by Kyoto ...
to recognize the sequestration of carbon. The additional units make it easier for them to achieve their target emission levels. It is estimated that forests absorb between each year, through photosynthetic conversion into
starch,
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell w ...
,
lignin, and other components of wooden
biomass. While this has been well documented for temperate forests and plantations, the
fauna
Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is ''funga''. Flora, fauna, funga and other forms of life are collectively referred to as ''Biota (ecology ...
of the tropical forests place some limitations for such global estimates.
Some countries seek to trade emission rights in carbon emission markets, purchasing the unused carbon emission allowances of other countries. If overall limits on
greenhouse gas emission
Greenhouse gas emissions from human activities strengthen the greenhouse effect, contributing to climate change. Most is carbon dioxide from burning fossil fuels: coal, oil, and natural gas. The largest emitters include coal in China and ...
are put into place,
cap and trade
Emissions trading is a market-based approach to controlling pollution by providing economic incentives for reducing the emissions of pollutants. The concept is also known as cap and trade (CAT) or emissions trading scheme (ETS). Carbon emission t ...
market mechanisms are purported to find cost-effective ways to reduce emissions. There is as yet no
carbon audit regime
A carbon audit regime is a means of accounting for quantifiable greenhouse gas control efforts. It establishes that the claimed reductions in emissions or enhancements of carbon sinks, has actually occurred and is stable.
See also
* Audit regi ...
for all such markets globally, and none is specified in the Kyoto Protocol. National carbon emissions are self-declared.
In the
Clean Development Mechanism
The Clean Development Mechanism (CDM) is a United Nations-run carbon offset scheme allowing countries to fund greenhouse gas emissions-reducing projects in other countries and claim the saved emissions as part of their own efforts to meet internat ...
, only
afforestation and
reforestation
Reforestation (occasionally, reafforestation) is the natural or intentional restocking of existing forests and woodlands (forestation) that have been depleted, usually through deforestation, but also after clearcutting.
Management
A debat ...
are eligible to produce
certified emission reduction
Certified Emission Reductions (CERs) are a type of emissions unit (or carbon credits) issued by the Clean Development Mechanism (CDM) Executive Board for emission reductions achieved by CDM projects and verified by a DOE (Designated Operational E ...
s (CERs) in the first commitment period of the Kyoto Protocol (2008–2012). Forest conservation activities or activities avoiding
deforestation
Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated ...
, which would result in emission reduction through the conservation of existing carbon stocks, are not eligible at this time. Also, agricultural carbon sequestration is not possible yet.
Storage in terrestrial and marine environments
Soils
Soils
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ter ...
represent a short to long-term carbon storage medium, and contain more carbon than all terrestrial vegetation and the atmosphere combined.
Plant litter
Plant litter (also leaf litter, tree litter, soil litter, litterfall or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that have fallen to the ground. This detritus or dead organic material and its constitue ...
and other
biomass including
charcoal accumulates as
organic matter in soils, and is degraded by
chemical weathering
Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement ...
and biological
degradation
Degradation may refer to:
Science
* Degradation (geology), lowering of a fluvial surface by erosion
* Degradation (telecommunications), of an electronic signal
* Biodegradation of organic substances by living organisms
* Environmental degradatio ...
. More recalcitrant
organic carbon polymers such as
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell w ...
,
hemi-cellulose,
lignin, aliphatic compounds, waxes and
terpenoid
The terpenoids, also known as isoprenoids, are a class of naturally occurring organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeably with "terpenes" ...
s are collectively retained as
humus. Organic matter tends to accumulate in litter and soils of colder regions such as the
boreal forest
Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic and Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of pines, spruc ...
s of North America and the
Taiga
Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic and Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of pines, spruc ...
of
Russia
Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eig ...
. Leaf litter and humus are rapidly oxidized and poorly retained in
sub-tropical
The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° north a ...
and tropical
climate
Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...
conditions due to high temperatures and extensive leaching by rainfall. Areas where
shifting cultivation
Shifting cultivation is an agricultural system in which plots of land are cultivated temporarily, then abandoned while post-disturbance fallow vegetation is allowed to freely grow while the cultivator moves on to another plot. The period of cu ...
or
slash and burn
Slash-and-burn agriculture is a farming method that involves the cutting and burning of plants in a forest or woodland to create a field called a swidden. The method begins by cutting down the trees and woody plants in an area. The downed veget ...
agriculture are practiced are generally only fertile for two to three years before they are abandoned. These tropical jungles are similar to coral reefs in that they are highly efficient at conserving and circulating necessary nutrients, which explains their lushness in a nutrient desert. Much
organic carbon
Total organic carbon (TOC) is the amount of carbon found in an organic compound and is often used as a non-specific indicator of water quality or cleanliness of pharmaceutical manufacturing equipment. TOC may also refer to the amount of organic c ...
retained in many agricultural areas worldwide has been severely depleted due to
intensive farming
Intensive agriculture, also known as intensive farming (as opposed to extensive farming), conventional, or industrial agriculture, is a type of agriculture, both of crop plants and of animals, with higher levels of input and output per unit of ...
practices.
Grassland
A grassland is an area where the vegetation is dominated by grasses ( Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur na ...
s contribute to
soil organic matter, stored mainly in their extensive fibrous root mats. Due in part to the climatic conditions of these regions (e.g. cooler temperatures and semi-arid to arid conditions), these soils can accumulate significant quantities of organic matter. This can vary based on rainfall, the length of the winter season, and the frequency of naturally occurring lightning-induced
grass-fires. While these fires release carbon dioxide, they improve the quality of the grasslands overall, in turn increasing the amount of carbon retained in the humic material. They also deposit carbon directly to the soil in the form of
Biochar
Biochar is the lightweight black residue, made of carbon and
ashes, remaining after the pyrolysis of biomass. Biochar is defined by the International Biochar Initiative as "the solid material obtained from the thermochemical conversion of ...
that does not significantly degrade back to carbon dioxide.
Forest fires release absorbed carbon back into the atmosphere, as does deforestation due to rapidly increased oxidation of soil organic matter.
Organic matter in
peat
Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficient ...
bogs undergoes slow
anaerobic decomposition below the surface. This process is slow enough that in many cases the bog grows rapidly and
fixes more carbon from the atmosphere than is released. Over time, the peat grows deeper. Peat bogs hold approximately one-quarter of the carbon stored in land plants and soils.
Under some conditions, forests and peat bogs may become sources of , such as when a forest is flooded by the construction of a hydroelectric dam. Unless the forests and peat are harvested before flooding, the rotting vegetation is a source of and
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...
comparable in magnitude to the amount of carbon released by a fossil-fuel powered plant of equivalent power.
Regenerative agriculture
Current agricultural practices lead to carbon loss from soils. It has been suggested that improved farming practices could improve the capacity of the
soil carbon sponge Soil carbon sponge (or soil sponge) is porous, well-aggregated soil in good health, better able to absorb and retain water. Australian microbiologist and climatologist, Walter Jehne, articulated the concept of the soil carbon sponge in his 2017 ...
to hold carbon and water. Present worldwide practises of
overgrazing
Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, game reserves, or nature res ...
are substantially reducing many grasslands' performance as soil carbon sponges.
The Rodale Institute
Rodale Institute is a non-profit organization that supports research into organic farming. It was founded in Emmaus, Pennsylvania in 1947 by J. I. Rodale, an organic living entrepreneur. After J.I. Rodale died in 1971, his son Robert Rodale purcha ...
says that
regenerative agriculture
Regenerative agriculture is a conservation and rehabilitation approach to food and farming systems. It focuses on topsoil regeneration, increasing biodiversity, improving the water cycle, enhancing ecosystem services, supporting biosequestration, ...
, if practiced on the planet's tillable land of , could sequester up to 40% of current emissions. They claim that agricultural carbon sequestration has the potential to mitigate global warming. When using biologically based regenerative practices, this dramatic benefit can be accomplished with no decrease in yields or farmer profits. Organically managed soils can convert carbon dioxide from a greenhouse gas into a food-producing asset.
In 2006, U.S. carbon dioxide emissions, largely from fossil fuel combustion, were estimated at nearly . If a per year sequestration rate was achieved on all of cropland in the United States, nearly of carbon dioxide would be sequestered per year, mitigating close to one quarter of the country's total fossil fuel emissions.
Riverine transport
![Terrestrial carbon escaping from inland waters](https://upload.wikimedia.org/wikipedia/commons/3/35/Terrestrial_carbon_escaping_from_inland_waters.jpg)
Terrestrial and marine ecosystems are chiefly connected through
riverine transport, which acts as the main channel through which erosive terrestrially derived substances enter into oceanic systems. Material and energy exchanges between the terrestrial
biosphere
The biosphere (from Greek βίος ''bíos'' "life" and σφαῖρα ''sphaira'' "sphere"), also known as the ecosphere (from Greek οἶκος ''oîkos'' "environment" and σφαῖρα), is the worldwide sum of all ecosystems. It can also ...
and the
lithosphere as well as
organic carbon
Total organic carbon (TOC) is the amount of carbon found in an organic compound and is often used as a non-specific indicator of water quality or cleanliness of pharmaceutical manufacturing equipment. TOC may also refer to the amount of organic c ...
fixation and oxidation processes together regulate ecosystem carbon and
dioxygen
There are several known allotropes of oxygen. The most familiar is molecular oxygen (O2), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O3). Others are:
* ...
(O
2) pools.
Riverine transport, being the main connective channel of these pools, will act to transport
net primary productivity (primarily in the form of
dissolved organic carbon
Dissolved organic carbon (DOC) is the fraction of organic carbon operationally defined as that which can pass through a filter with a pore size typically between 0.22 and 0.7 micrometers. The fraction remaining on the filter is called partic ...
(DOC) and
particulate organic carbon
Particulate organic matter (POM) is a fraction of total organic matter operationally defined as that which does not pass through a filter pore size that typically ranges in size from 0.053 to 2 millimeters.
Particulate organic carbon (POC) is ...
(POC)) from terrestrial to oceanic systems. During transport, part of DOC will rapidly return to the atmosphere through
redox reaction
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
s, causing "carbon degassing" to occur between land-atmosphere storage layers. The remaining DOC and
dissolved inorganic carbon
Dissolved inorganic carbon (DIC) is the sum of the aqueous species of inorganic carbon in a solution. Carbon compounds can be distinguished as either organic or inorganic, and as dissolved or particulate, depending on their composition. Organic ...
(DIC) are also exported to the ocean.
Currently (2015) inorganic and organic carbon export fluxes from global rivers to the ocean amount to 0.50–0.70
Pg C y
−1 and 0.15–0.35 Pg C y
−1 respectively.
On the other hand, POC can remain buried in sediment over an extensive period, and the annual global terrestrial to oceanic POC flux has been estimated at 0.20
(+0.13,-0.07) Gg C y
−1.
Oceans
Enhancing natural sequestration
Forests
Forests can be carbon stores, and they are carbon dioxide sinks when they are increasing in density or area. In
Canada's boreal forests as much as 80% of the total carbon is stored in the soils as dead organic matter.
A 40-year study of African, Asian, and South American
tropical forest
Tropical forests (a.k.a. jungle) are forested landscapes in tropical regions: ''i.e.'' land areas approximately bounded by the tropic of Cancer and Capricorn, but possibly affected by other factors such as prevailing winds.
Some tropical fore ...
s by the University of Leeds showed that tropical forests absorb about 18% of all carbon dioxide added by fossil fuels. For the last three decades, the amount of carbon absorbed by the world's intact tropical forests has fallen, according to a study published in 2020 in the journal Nature.
![Proportion of carbon stock in forest carbon pools, 2020](https://upload.wikimedia.org/wikipedia/commons/9/90/Proportion_of_carbon_stock_in_forest_carbon_pools%2C_2020.svg)
The total carbon stock in forests decreased from 668 gigatonnes in 1990 to 662 gigatonnes in 2020. However, another study finds that the
leaf area index has increased globally since 1981, which was responsible for 12.4% of the accumulated terrestrial carbon sink from 1981 to 2016. The
CO2 fertilization effect, on the other hand, was responsible for 47% of the sink, while climate change reduced the sink by 28.6%.
In 2019 they took up a third less carbon than they did in the 1990s, due to higher temperatures, droughts and deforestation. The typical tropical forest may become a carbon source by the 2060s. Truly mature tropical forests, by definition, grow rapidly, with each tree producing at least 10 new trees each year. Based on studies by
FAO
The Food and Agriculture Organization of the United Nations (FAO)french: link=no, Organisation des Nations unies pour l'alimentation et l'agriculture; it, Organizzazione delle Nazioni Unite per l'Alimentazione e l'Agricoltura is an intern ...
and
UNEP
The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on ...
, it has been estimated that Asian forests absorb about 5 tonnes of carbon dioxide per hectare each year. The global cooling effect of carbon sequestration by forests is partially counterbalanced in that reforestation can decrease the reflection of sunlight (
albedo
Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refl ...
). Mid-to-high-latitude forests have a much lower
albedo
Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refl ...
during snow seasons than flat ground, thus contributing to warming. Modeling that compares the effects of albedo differences between forests and grasslands suggests that expanding the land area of forests in temperate zones offers only a temporary cooling benefit.
In the United States in 2004 (the most recent year for which EPA statistics are available), forests sequestered 10.6% (637
megatonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton (United States c ...
s)
of the carbon dioxide released in the United States by the combustion of fossil fuels (coal, oil, and natural gas; 5,657 megatonnes
). Urban trees sequestered another 1.5% (88 megatonnes).
To further reduce U.S. carbon dioxide emissions by 7%, as stipulated by the
Kyoto Protocol, would require the planting of "an area the size of Texas
% of the area of Brazilevery 30 years".
Carbon offset
A carbon offset is a reduction or removal of emissions of carbon dioxide or other greenhouse gases made in order to compensate for emissions made elsewhere. Offsets are measured in tonnes of carbon dioxide-equivalent (CO2e). One ton of carb ...
programs are planting millions of fast-growing trees per year to reforest tropical lands, for as little as $0.10 per tree; over their typical 40-year lifetime, one million of these trees will fix 1 a million tons of carbon dioxide. In Canada, reducing timber harvesting would have very little impact on carbon dioxide emissions because of the combination of harvest and stored carbon in manufactured wood products along with the regrowth of the harvested forests. Additionally, the amount of carbon released from harvesting is small compared to the amount of carbon lost each year to forest fires and other natural disturbances.
The
Intergovernmental Panel on Climate Change concluded that "a sustainable forest management strategy aimed at maintaining or increasing forest carbon stocks, while producing an annual sustained yield of timber fibre or energy from the forest, will generate the largest sustained mitigation benefit". Sustainable management practices keep forests growing at a higher rate over a potentially longer period of time, thus providing net sequestration benefits in addition to those of unmanaged forests.
Life expectancy of forests varies throughout the world, influenced by tree species, site conditions and natural disturbance patterns. In some forests, carbon may be stored for centuries, while in other forests, carbon is released with frequent stand replacing fires. Forests that are harvested prior to stand replacing events allow for the retention of carbon in manufactured forest products such as lumber. However, only a portion of the carbon removed from logged forests ends up as durable goods and buildings. The remainder ends up as sawmill by-products such as pulp, paper and pallets, which often end with incineration (resulting in carbon release into the atmosphere) at the end of their lifecycle. For instance, of the 1,692 megatonnes of carbon harvested from forests in
Oregon
Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idaho. T ...
and
Washington
Washington commonly refers to:
* Washington (state), United States
* Washington, D.C., the capital of the United States
** A metonym for the federal government of the United States
** Washington metropolitan area, the metropolitan area centered o ...
from 1900 to 1992, only 23% is in long-term storage in forest products.
Oceans
One way to increase the carbon sequestration efficiency of the oceans is to add micrometre-sized iron particles in the form of either
hematite (iron oxide) or
melanterite
Melanterite is a mineral form of hydrous iron(II) sulfate: FeSO4·7H2O. It is the iron analogue of the copper sulfate chalcanthite. It alters to siderotil by loss of water. It is a secondary sulfate mineral which forms from the oxidation of pri ...
(iron sulfate) to certain regions of the ocean. This has the effect of stimulating growth of
plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
. Iron is an important nutrient for
phytoplankton, usually made available via upwelling along the
continental shelves, inflows from rivers and streams, as well as deposition of dust suspended in the
atmosphere. Natural sources of ocean iron have been declining in recent decades, contributing to an overall decline in ocean productivity.
Yet in the presence of iron nutrients plankton populations quickly grow, or 'bloom', expanding the base of
biomass productivity throughout the region and removing significant quantities of from the atmosphere via
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
. A test in 2002 in the
Southern Ocean
The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-small ...
around
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
suggests that between 10,000 and 100,000 carbon atoms are sunk for each iron atom added to the water. Application of iron nutrients in select parts of the oceans, at appropriate scales, could have the combined effect of restoring ocean productivity while at the same time mitigating the effects of human caused emissions of carbon dioxide to the atmosphere.
Because the effect of periodic small scale phytoplankton blooms on ocean ecosystems is unclear, more studies would be helpful. Phytoplankton have a complex effect on cloud formation via the release of substances such as
dimethyl sulfide (DMS) that are converted to sulfate aerosols in the atmosphere, providing
cloud condensation nuclei, or CCN.
Other nutrients such as nitrates, phosphates, and silica as well as iron may cause ocean fertilization. There has been some speculation that using pulses of fertilization (around 20 days in length) may be more effective at getting carbon to ocean floor than sustained fertilization.
There is some controversy over seeding the oceans with iron however, due to the potential for increased toxic phytoplankton growth (e.g. "
red tide
A harmful algal bloom (HAB) (or excessive algae growth) is an algal bloom that causes negative impacts to other organisms by production of natural algae-produced toxins, mechanical damage to other organisms, or by other means. HABs are sometimes ...
"), declining water quality due to overgrowth, and increasing anoxia in areas harming other sea-life such as zooplankton, fish, coral, etc.
Soils
Since the 1850s, a large proportion of the world's grasslands have been tilled and converted to croplands, allowing the rapid oxidation of large quantities of soil organic carbon. However, in the United States in 2004 (the most recent year for which EPA statistics are available), agricultural soils including pasture land sequestered 0.8% (46 megatonne)
as much carbon as was released in the United States by the combustion of fossil fuels (5,988 megatonne).
The annual amount of this sequestration has been gradually increasing since 1998.
Methods that significantly enhance carbon sequestration in soil include
no-till farming
No-till farming (also known as zero tillage or direct drilling) is an agricultural technique for growing crops or pasture without disturbing the soil through tillage. No-till farming decreases the amount of soil erosion tillage causes in certai ...
, residue mulching,
cover cropping, and
crop rotation
Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. It reduces reliance on one set of nutrients, pest and weed pressure, and the probability of developing resistant ...
, all of which are more widely used in
organic farming
Organic farming, also known as ecological farming or biological farming,Labelling, article 30 o''Regulation (EU) 2018/848 of the European Parliament and of the Council of 30 May 2018 on organic production and labelling of organic products and re ...
than in conventional farming. Because only 5% of US farmland currently uses no-till and residue mulching, there is a large potential for carbon sequestration. Conversion to pastureland, particularly with good management of grazing, can sequester even more carbon in the soil.
Terra preta
''Terra preta'' (, locally , literally "black soil" in Portuguese) is a type of very dark, fertile anthropogenic soil ( anthrosol) found in the Amazon Basin. It is also known as "Amazonian dark earth" or "Indian black earth". In Portuguese its f ...
, an
anthropogenic, high-carbon soil, is also being investigated as a sequestration mechanism.
By
pyrolysing biomass, about half of its carbon can be reduced to
charcoal, which can persist in the soil for centuries, and makes a useful soil amendment, especially in tropical soils (''
biochar
Biochar is the lightweight black residue, made of carbon and
ashes, remaining after the pyrolysis of biomass. Biochar is defined by the International Biochar Initiative as "the solid material obtained from the thermochemical conversion of ...
'' or ''agrichar'').
"For most of human history, permafrost has been Earth's largest terrestrial carbon sink, trapping plant and animal material in its frozen layers for centuries. It currently stores about 1,600 billion tonnes of carbon—more than twice the amount in the atmosphere today. But thanks to rising temperatures, permafrost is fracturing and disappearing".
Sergey Zimov
Sergey Aphanasievich Zimov (russian: Сергей Афанасьевич Зимов; b. 18 July 1955) is a Russian geophysicist who specialises in arctic and subarctic ecology. He is the Director of Northeast Scientific Station (a research institut ...
has proposed to restore and protect this major carbon sequestration mechanism via restoration of grassland and large arctic mammalian herbivores.
Savanna
Controlled burns on far north Australian
savanna
A savanna or savannah is a mixed woodland- grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...
s can result in an overall carbon sink. One working example is the West Arnhem Fire Management Agreement, started to bring "strategic fire management across 28,000 km
2 of Western Arnhem Land". Deliberately starting controlled burns early in the dry season results in a mosaic of burnt and unburnt country which reduces the area of burning compared with stronger, late dry season fires. In the early dry season there are higher moisture levels, cooler temperatures, and lighter wind than later in the dry season; fires tend to go out overnight. Early controlled burns also results in a smaller proportion of the grass and tree biomass being burnt.
[ ] Emission reductions of 256,000 tonnes of have been made as of 2007.
[ ]
Artificial sequestration
For carbon to be sequestered artificially (i.e. not using the natural processes of the carbon cycle) it must first be captured, ''or'' it must be significantly delayed or prevented from being re-released into the atmosphere (by combustion, decay, etc.) from an existing carbon-rich material, by being incorporated into an enduring usage (such as in construction). Thereafter it can be passively stored ''or'' remain productively utilized over time in a variety of ways. For instance, upon harvesting, wood (as a carbon-rich material) can be immediately burned or otherwise serve as a fuel, returning its carbon to the atmosphere, ''or'' it can be incorporated into construction or a range of other durable products, thus sequestering its carbon over years or even centuries.
A very carefully designed and durable, energy-efficient and energy-capturing building has the potential to sequester (in its carbon-rich construction materials), as much as or more carbon than was released by the acquisition and incorporation of all its materials and than will be released by building-function "energy-imports" during the structure's (potentially multi-century) existence. Such a structure might be termed "carbon neutral" or even "carbon negative". Building construction and operation (electricity usage, heating, etc.) are estimated to contribute nearly ''half'' of the annual human-caused carbon additions to the atmosphere.
Natural-gas
Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbon di ...
purification plants often already have to remove carbon dioxide, either to avoid
dry ice
Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily ...
clogging gas tankers or to prevent carbon-dioxide concentrations exceeding the 3% maximum permitted on the natural-gas distribution grid.
Buildings
![Mjøstårnet](https://upload.wikimedia.org/wikipedia/commons/3/30/Mj%C3%B8st%C3%A5rnet.jpg)
According to an international team of interdisciplinary scientists in a 2020 study, broad-base adoption of
mass timber and their substitution for steel and concrete in new mid-rise construction projects over the next few decades has the potential to turn
timber buildings into a global carbon sink, as they store the carbon dioxide taken up from the air by trees that are harvested and used as mass timber. Noting the demographic need for new urban construction for the next thirty years, the team analyzed four scenarios for the transition to mass-timber new mid-rise construction. Assuming business as usual, only 0.5% of new buildings worldwide would be constructed with timber by 2050 (scenario 1). This could be driven up to 10% (scenario 2) or 50% (scenario 3), assuming mass timber manufacturing would increase as a material revolution replacing cement and steel in urban construction by wood scales up accordingly. Lastly, if countries with current low industrialization level, e.g., Africa, Oceania, and parts of Asia, would also make the transition to timber (including bamboo), then even 90% timber by 2050 (scenario 4) is conceivable. This could result in storing between 10 million tons of carbon per year in the lowest scenario and close to 700 million tons in the highest scenario. The study found that this potential could be realized under two conditions. First, the harvested forests would need to be sustainably managed, governed, and used. Second, wood from demolished timber buildings would need to be reused or preserved on land in various forms.
Direct air capture
Oceans
Another proposed form of carbon sequestration in the ocean is direct injection. In this method, carbon dioxide is pumped directly into the water at depth, and expected to form "lakes" of liquid at the bottom. Experiments carried out in moderate to deep waters () indicate that the liquid reacts to form solid
clathrate hydrates, which gradually dissolve in the surrounding waters.
This method, too, has potentially dangerous environmental consequences. The carbon dioxide does react with the water to form
carbonic acid, ; however, most (as much as 99%) remains as dissolved molecular . The equilibrium would no doubt be quite different under the high pressure conditions in the deep ocean. In addition, if deep-sea bacterial
methanogens that reduce carbon dioxide were to encounter the carbon dioxide sinks, levels of
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...
gas may increase, leading to the generation of an even worse greenhouse gas.
The resulting environmental effects on
benthic life forms of the
bathypelagic,
abyssopelagic
The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. "Abyss" derives from the Greek word , meaning bottomless. At depths of , this zone remains in perpetual darkness. It covers 83% of the total area of the ocean ...
and
hadopelagic zones are unknown. Even though life appears to be rather sparse in the deep ocean basins, energy and chemical effects in these deep basins could have far-reaching implications. Much more work is needed here to define the extent of the potential problems.
Carbon storage in or under oceans may not be compatible with the
.
An additional method of long-term ocean-based sequestration is to gather
crop residue
Crop residues are materials left in an agricultural field after the crop has been harvested. These residues include stalks and stubble (stems), leaves and seed pods. Good management of field residues can increase efficiency of irrigation and c ...
such as corn stalks or excess hay into large weighted bales of biomass and deposit it in the
alluvial fan
An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but a ...
areas of the deep
ocean basin
In hydrology, an oceanic basin (or ocean basin) is anywhere on Earth that is covered by seawater. Geologically, ocean basins are large geologic basins that are below sea level.
Most commonly the ocean is divided into basins fol ...
. Dropping these residues in alluvial fans would cause the residues to be quickly buried in silt on the sea floor, sequestering the biomass for very long time spans. Alluvial fans exist in all of the world's oceans and seas where river deltas fall off the edge of the
continental shelf such as the
Mississippi alluvial fan in the
gulf of Mexico
The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...
and the
Nile alluvial fan in the
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...
. A downside, however, would be an increase in aerobic bacteria growth due to the introduction of biomass, leading to more competition for oxygen resources in the deep sea, similar to the
oxygen minimum zone
The oxygen minimum zone (OMZ), sometimes referred to as the shadow zone, is the zone in which oxygen saturation in seawater in the ocean is at its lowest. This zone occurs at depths of about , depending on local circumstances. OMZs are found worl ...
.
Geological sequestration
The method of ''geo-sequestration'' or ''geological storage'' involves injecting carbon dioxide directly into underground geological formations. Declining
oil fields, saline
aquifer
An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials ( gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characteris ...
s, and unmineable
coal seam
Coal mining is the process of extracting coal from the ground. Coal is valued for its energy content and since the 1880s has been widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron fro ...
s have been suggested as storage sites. Caverns and old mines that are commonly used to store natural gas are not considered, because of a lack of storage safety.
has been injected into declining oil fields for more than 40 years, to increase oil recovery. This option is attractive because the storage costs are offset by the sale of additional oil that is recovered. Typically, 10–15% additional recovery of the original oil in place is possible. Further benefits are the existing infrastructure and the geophysical and geological information about the oil field that is available from the oil exploration. Another benefit of injecting into oil fields is that is soluble in oil. Dissolving in oil lowers the viscosity of the oil and reduces its interfacial tension which increases the oils mobility. All oil fields have a geological barrier preventing upward migration of oil. As most oil and gas has been in place for millions to tens of millions of years, depleted oil and gas reservoirs can contain carbon dioxide for millennia. Identified possible problems are the many 'leak' opportunities provided by old oil wells, the need for high injection pressures and acidification which can damage the geological barrier. Other disadvantages of old oil fields are their limited geographic distribution and depths, which require high injection pressures for sequestration. Below a depth of about 1000 m, carbon dioxide is injected as a supercritical fluid, a material with the density of a liquid, but the viscosity and diffusivity of a gas.
Unmineable coal seams can be used to store , because absorbs to the coal surface, ensuring safe long-term storage. In the process it releases methane that was previously adsorbed to the coal surface and that may be recovered. Again the sale of the methane can be used to offset the cost of the storage. Release or burning of methane would of course at least partially offset the obtained sequestration result – except when the gas is allowed to escape into the atmosphere in significant quantities: methane has a 80-fold higher
global warming potential
Global warming potential (GWP) is the heat absorbed by any greenhouse gas in the atmosphere, as a multiple of the heat that would be absorbed by the same mass of carbon dioxide (). GWP is 1 for . For other gases it depends on the gas and the time ...
than (during the first twenty years).
Saline aquifers contain highly mineralized brines and have so far been considered of no benefit to humans except in a few cases where they have been used for the storage of chemical waste. Their advantages include a large potential storage volume and relatively common occurrence reducing the distance over which has to be transported. The major disadvantage of saline aquifers is that relatively little is known about them compared to oil fields. Another disadvantage of saline aquifers is that as the salinity of the water increases, less can be dissolved into aqueous solution. To keep the cost of storage acceptable the geophysical exploration may be limited, resulting in larger uncertainty about the structure of a given aquifer. Unlike storage in oil fields or coal beds, no side product will offset the storage cost. Leakage of back into the atmosphere may be a problem in saline-aquifer storage. However, current research shows that several ''trapping mechanisms'' immobilize the underground, reducing the risk of leakage.
A major research project examining the geological sequestration of carbon dioxide is currently being performed at an oil field at
Weyburn
Weyburn is the eleventh-largest city in Saskatchewan, Canada. The city has a population of 10,870. It is on the Souris River southeast of the provincial capital of Regina and is north from the North Dakota border in the United States. The n ...
in south-eastern
Saskatchewan
Saskatchewan ( ; ) is a province in western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on the south by the U.S. states of Montana and North Dak ...
. In the
North Sea
The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea, epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the ...
, Norway's
Equinor
Equinor ASA (formerly Statoil and StatoilHydro) is a Norwegian state-owned multinational energy company headquartered in Stavanger. It is primarily a petroleum company, operating in 36 countries with additional investments in renewable energy. I ...
natural-gas platform
Sleipner strips carbon dioxide out of the natural gas with amine solvents and disposes of this carbon dioxide by geological sequestration. Sleipner reduces emissions of carbon dioxide by approximately one million tonnes a year. The cost of geological sequestration is minor relative to the overall running costs. One of the first planned trial of large-scale sequestration of carbon dioxide stripped from power plant emissions in the
Miller oilfield
The Miller oilfield is a deep reservoir under the North Sea, 240 kilometres north-east of Peterhead in UKCS Blocks 16/7b and 16/8b. It was discovered in 1983 by BP in a water depth of 100 metres. Production from Miller field started in June 1992 ...
as its reserves are depleted by
BP was not funded.
In October 2007, the
Bureau of Economic Geology at
The University of Texas at Austin
The University of Texas at Austin (UT Austin, UT, or Texas) is a public research university in Austin, Texas. It was founded in 1883 and is the oldest institution in the University of Texas System. With 40,916 undergraduate students, 11,075 ...
received a 10-year, $38 million subcontract to conduct the first intensively monitored, long-term project in the United States studying the feasibility of injecting a large volume of for underground storage. The project is a research program of th
Southeast Regional Carbon Sequestration Partnership (SECARB) funded by the
National Energy Technology Laboratory
The National Energy Technology Laboratory (NETL) is a U.S national laboratory under the Department of Energy Office of Fossil Energy. NETL focuses on applied research for the clean production and use of domestic energy resources. NETL perform ...
of the
U.S. Department of Energy (DOE). The SECARB partnership will demonstrate injection rate and storage capacity in the
Tuscaloosa
Tuscaloosa ( ) is a city in and the seat of Tuscaloosa County in west-central Alabama, United States, on the Black Warrior River where the Gulf Coastal and Piedmont plains meet. Alabama's fifth-largest city, it had an estimated population of ...
-
Woodbine geologic system that stretches from Texas to Florida. Beginning in fall 2007, the project will inject at the rate of one million tons per year, for up to 1.5 years, into brine up to below the land surface near the
Cranfield oil field about east of
Natchez, Mississippi. Experimental equipment will measure the ability of the subsurface to accept and retain .
Mineral sequestration
Mineral sequestration aims to trap carbon in the form of solid
carbonate
A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate ...
salts. This process occurs slowly in nature and is responsible for the deposition and accumulation of
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
over geologic time.
Carbonic acid in groundwater slowly reacts with complex
silicates to dissolve
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
,
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
,
alkalis and
silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
and leave a residue of
clay minerals. The dissolved calcium and magnesium react with
bicarbonate
In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula .
Bicarbonate serves a crucial biochem ...
to precipitate calcium and magnesium carbonates, a process that organisms use to make shells. When the organisms die, their shells are deposited as sediment and eventually turn into limestone. Limestones have accumulated over billions of years of geologic time and contain much of Earth's carbon. Ongoing research aims to speed up similar reactions involving alkali carbonates.
Several serpentinite deposits are being investigated as potentially large scale storage sinks such as those found in NSW, Australia, where the first mineral carbonation pilot plant project is underway. Beneficial re-use of magnesium carbonate from this process could provide feedstock for new products developed for the built environment and agriculture without returning the carbon into the atmosphere and so acting as a carbon sink.
[
One proposed reaction is that of the olivine-rich rock ]dunite
Dunite (), also known as olivinite (not to be confused with the mineral olivenite), is an intrusive igneous rock of ultramafic composition and with phaneritic (coarse-grained) texture. The mineral assemblage is greater than 90% olivine, with ...
, or its hydrated equivalent serpentinite
Serpentinite is a rock composed predominantly of one or more serpentine group minerals, the name originating from the similarity of the texture of the rock to that of the skin of a snake. Serpentinite has been called ''serpentine'' or ''se ...
with carbon dioxide to form the carbonate mineral magnesite, plus silica and iron oxide (magnetite
Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With th ...
).
Serpentinite sequestration is favored because of the non-toxic and stable nature of magnesium carbonate. The ideal reactions involve the magnesium endmember components of the olivine
The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...
(reaction 1) or serpentine (reaction 2), the latter derived from earlier olivine by hydration and silicification (reaction 3). The presence of iron in the olivine or serpentine reduces the efficiency of sequestration, since the iron components of these minerals break down to iron oxide and silica (reaction 4).
Serpentinite reactions
Zeolitic imidazolate frameworks
Zeolitic imidazolate frameworks is a metal-organic framework carbon dioxide sink which could be used to keep industrial emissions of carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
out of the atmosphere.
Trends in sink performance
One study in 2009 found that the fraction of fossil-fuel emissions absorbed by the oceans may have declined by up to 10% since 2000, indicating oceanic sequestration may be sublinear.[''Earth Institute News''](_blank)
Columbia University, 18 November 2009 Another 2009 study found that the fraction of absorbed by terrestrial ecosystems and the oceans has not changed since 1850, indicating undiminished capacity.
One study in 2020 found that 32 tracked Brazilian non-Amazon seasonal tropical forests declined from a carbon sink to a carbon source in 2013 and concludes that "policies are needed to mitigate the emission of greenhouse gases and to restore and protect tropical seasonal forests".
The IPCC has noted that oceans and vegetation will progressively absorb a smaller fraction of emissions and, in return, create a larger absorption shortcoming.
An emerging trend is the use of conservative or regenerative agriculture. According to Project Drawdown, regenerative agriculture could sink 9.43 to 13.4 gigatons of between 2020 and 2050. This will be a huge contribution to sink performance.
See also
* Azolla event
The Azolla event is a scenario hypothesized to have occurred in the middle Eocene epoch, around , when blooms of the freshwater fern ''Azolla'' are thought to have happened in the Arctic Ocean. As they sank to the stagnant sea floor, over a per ...
* Biochar
Biochar is the lightweight black residue, made of carbon and
ashes, remaining after the pyrolysis of biomass. Biochar is defined by the International Biochar Initiative as "the solid material obtained from the thermochemical conversion of ...
* Bio-energy with carbon capture and storage
Bioenergy with carbon capture and storage (BECCS) is the process of extracting bioenergy from biomass and capturing and storing the carbon, thereby removing it from the atmosphere. The carbon in the biomass comes from the greenhouse gas carbon ...
* Carbon capture and storage
Carbon capture and storage (CCS) or carbon capture and sequestration is the process of capturing carbon dioxide (CO2) before it enters the atmosphere, transporting it, and storing it (carbon sequestration) for centuries or millennia. Usually th ...
* Carbon cycle
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Carbon is the main component of biological compounds as well as a major componen ...
* Carbon sequestration in terrestrial ecosystems
* Carbon sinks and removal for climate change mitigation
* Fluxnet-Canada Research Network, research initiative on post forest disturbance carbon sinking
Sources
References
External links
Carbon Capture and Sequestration Technologies Program at MIT
{{DEFAULTSORT:Carbon Sink
Carbon dioxide
Carbon dioxide removal
Photosynthesis
Gas technologies