Carbon is the basis of all life but, as carbon dioxide (CO2), it is a major problem for our climate. Yet, only a small proportion is in the air at all. Much larger carbon storage mediums are forests, soils or oceans.
What is carbon storage?
Carbon (“C” as a chemical element) is present everywhere around us. Amongst other things, it is the basic element for sugars, fats, wood, proteins and much more. Therefore, wherever there is life, there is also a carbon store.¹
Where carbon occurs in chemical molecules, we usually speak of organic chemistry, because carbon is the basis of all life. As such, it is permanently transformed and goes through a continuous cycle, the carbon cycle.
Plants take up carbon from the atmosphere in the form of CO2 and convert it into sugar by means of photosynthesis, producing oxygen as a “waste product”, so to speak. The sugar either serves as an energy supplier for the metabolism or it is processed into other carbon-containing products.
These products are then absorbed again by us or other living creatures as food. Through our breathing or through the rotting of fallen leaves, for example, carbon is released again in the form of CO2.
Carbon is also released during fires, and in some conversion processes, methane is also produced. But, not all carbon is released again, some of it also remains bound in place – in the soil, in the trees or elsewhere. These are then carbon reservoirs in which the carbon dioxide remains, sometimes for decades or centuries.²
Soil as carbon storage
The soil is said to be the most important carbon store on our planet: about half of the soil consists of carbon bound in humus i.e. in dead and partially transformed plant remains.
According to the Heinrich Böll Foundation, our soils contain more carbon than all plants on earth and in the atmosphere combined. At the same time, soils are also major sources of CO2.
While part of the carbon remains in the soil for decades to millennia, microorganisms rapidly convert another part. In this way, part of the carbon is released back into the atmosphere in the form of carbon dioxide. Current measurements and forecasts indicate that global warming caused by the climate crisis will accelerate these conversion processes. This means that microorganisms will probably work more actively in the future and thus release more CO2, according to the Heinrich Böll Foundation.
Exactly how much carbon can be sequestered in the soil, and how long the carbon remains in the soil, is difficult to measure and therefore estimate. What is certain, however, is that agriculture is putting our soils at risk, for example through soil erosion, and is constantly losing soil fertility.³
Forests as carbon stores
Forests cover about 30 per cent of our land surface worldwide. In total, all plants worldwide store 700 billion tonnes of carbon.
According to the WWF, tropical rainforests store 50 per cent more carbon than other forests due to their large biomass reserves. Plants are particularly important, as thanks to photosynthesis, they are the only living creatures that can filter CO2 out of the air and absorb it again. They are the ones that make the formation of humus and peat possible in the first place.
The WWF points out another important function of forests, given that they essentially act as huge air conditioning systems. They participate in the water cycle by evaporating water through the sun and thus cooling the atmosphere. However, these two important functions are under immense threat worldwide due to mass deforestation.
Carbon storage in the sea
Large quantities of carbon are stored not only on land. According to studies, the world’s oceans absorb the largest amount of carbon where they provide 50 per cent of the oxygen on earth.⁵ Two key processes are involved in storing carbon in the sea:
- Phytoplankton, algae and seaweeds work very much like trees. They carry out photosynthesis and thus convert CO2 into organic compounds.
- The second process works entirely without plants. Carbon dioxide dissolves naturally in the oceans, and about 91 per cent is converted into hydrogen carbonate. There is a constant exchange between the atmosphere and the ocean, and whether the ocean absorbs CO2 depends on various factors, but primarily atmospheric pressure and temperature. If there is a lot of carbon dioxide in the air, it puts pressure on the water, so to speak, and the ocean absorbs more CO2. However, the warmer the oceans are, the less CO2 they can absorb.
The CO2 dissolved in the water is then transported by ocean currents into the depths of the ocean, where it remains for a prolonged period of time. However, this doesn’t come without problems. To convert CO2 into hydrogen carbonate, carbonate or water is needed. The carbonate therefore decomposes and is then no longer available to marine organisms such as corals, which need it to form shells and skeletal structures.
A natural factory
Our earth is an incredible natural factory, providing us with all that we need in order to thrive. However, through excess man-made carbon emissions, we are damaging our planet and causing irreversible change. Climate change is an extremely real threat to human existence, and everyone must play their part in stopping it or, at least, slowing it down.
¹ What is carbon?, https://www.theguardian.com/environment/2011/feb/03/carbon
² The Carbon Cycle, https://earthobservatory.nasa.gov/features/CarbonCycle
³ Soil as Carbon Storehouse: New Weapon in Climate Fight?, https://e360.yale.edu/features/soil_as_carbon_storehouse_new_weapon_in_climate_fight#:~:text=Scientists%20say%20that%20more%20carbon,in%20plant%20and%20animal%20life.
⁴ Forest carbon, https://www.nrcan.gc.ca/climate-change/impacts-adaptations/climate-change-impacts-forests/forest-carbon/13085
⁵ Ocean Storage of CO2, https://www.maritime-executive.com/features/ocean-storage-of-co2