Carbon sinks are natural locations that absorb carbon dioxide from the atmosphere to dilute the concentration of carbon in the air. Carbon sinks can be both natural such as oceans and soil as well as artificial like chemicals and technologies that sequester carbon and make it possible to store it away from the open atmosphere. After the passage of Kyoto Protocol that recognizes the importance of carbon sinks in offsetting the rise of greenhouse gas (GHG) emissions, there has been special focus on carbon sinks.
The importance of carbon sinks as a solution to rising levels of GHG emissions is today well-recognized and now the governments and organizations are making efforts to create new carbon sinks while increasing the efficiency of the existing ones. The latest to provide momentum to the carbon sink drive are some very promising technologies that promise to remove carbon from the atmosphere and store it in a safe manner.
Oceans as carbon sinks
Oceans are the biggest carbon sinks having absorbed half of the CO2 emissions since the industrial revolution. Oceans readily absorb carbon dioxide from the atmosphere as well as sequester and store carbon in its ecosystem. They are the largest storehouse of carbon.
The oceanic system across the globe represents a continuous process of equilibration between the CO2 in oceanic waters and the atmosphere. The Oceans’ surface releases 88,000 million tons of carbon and absorbs 90,000 million tons of carbon every year. So, the oceans represent the uptake of about 2,000 million tons of carbon each year.
Woodland/grassland soil and plants
Woodland or grassland is another major carbon sink. Here, plants and trees absorb a great deal of carbon dioxide from the atmosphere through the process of photosynthesis. They retain much of the carbon in their leaves and branches while releasing oxygen back to the atmosphere. After maturing, their leaves and branches fall to the ground and decay into the soil, depositing much of the carbon content in the soil.
In this process, the entire plant life cycle is engaged in carbon sequestering. In a natural woodland or grassland, there is little harvesting of wood or leaves and that makes them a net carbon sink that does not send back any carbon in the atmosphere. On the contrary, it releases clean oxygen that is critical for the existence of humans and animals.
Wetlands and peat bogs
Wetland soil is rich in carbon as these are one of the most efficient carbon sinks available on the earth. About 15% of the soil carbon in the world is stored in wetland soils while their area is limited to only 6% of the world’s total land. Wetlands near the sea covered under mangroves are very efficient natural carbon sinks.
Peat bogs found inside the marshy land near the sea is another great carbon sink. Peat bogs are partly -decomposed biomass that would have become totally decayed or decomposed. Though there is a difference of opinion about how much of the peat bogs act as carbon sink and how much of it act as a source of carbon around the world in different periods of time. However, on the whole, by increasing the area under peat bogs, a good deal of carbon can be stored.
Farm soil in regenerative agriculture
Agricultural activities act both as the source and the storage of carbon. When the soil is dug up for farming, carbon stored in the soil gets released. But when the plants come up, the process of photosynthesis begins which in turn absorbs carbon dioxide from the atmosphere and gives back fresh oxygen. This dilutes the concentration of carbon in the atmosphere and helps bring down the temperature.
In particular, regenerative agriculture is good for removing carbon from the atmosphere and storing them in plants and soil. It’s a farming technique that aims to regenerate the topsoil, increase biodiversity, and improve water cycle. The objective of regenerative agriculture is to stop land degradation by inadequate land use and management.
Carbon farming (bamboo, seaweed)
Bamboo and seaweed sequester carbon from their atmosphere and use up to create huge amounts of biomass. They enrich the environment by removing carbon and releasing oxygen into it. They also deposit and store carbon in the soil in significant quantities. They have the ability to remove carbon from the air faster than any other plant.
Bamboo can grow and thrive on degraded and inhospitable lands. It brings the benefits of photosynthesis in areas where the plant life is not as robust and varied as it can be elsewhere. Its concentration of carbon can be gauged from the fact that the bamboo has strength and tensile of concrete and steel respectively. Bamboos can grow to their full size in one season. After that, these can be harvested or left to mature.
Similarly, seaweed consumes a lot of carbon to create an all pervasive biomass in the shallow ocean. It also undergoes the process of photosynthesis that releases oxygen. Seaweeds host a range of marine life and are an important part of its ecosystem..
Composting & mulching soil with compost
An important method of increasing farm productivity is the use of compost and mulching of soil with compost. Preparing compost itself is a useful way of storing carbon in the soil. When we put biomass in the earth and leave it decompose, much of the carbon in it gets stored in the soil. When we use compost in the topsoil, it transfers much of the carbon in it to the soil, thereby, increasing the health of the topsoil. This boosts the yield and the plant health.
A stronger and robust plant would engage in a more vigorous process of photosynthesis and, thereby, consume more carbon from the atmosphere and increase its biomass. Composting is an effective way to stop GHG emission from the biomass. It also helps store and transfer its carbon content to the topsoil and in turn increase the fertility of the land.
Underground injection of CO2 at hydrocarbon refining plants
Another very interesting and productive way of getting rid of carbon dioxide from the atmosphere is using it in enhanced oil recovery (EOR). At hydrocarbon refining units, carbon is either captured or produced to use it in EOR activities. It is compressed and transported to oil rigs where it is strategically injected into the underground. The compressed CO2 mobilizes and drives the underground oil and gas reserves to come out faster through the outlet well. Oil extraction companies both capture and produce CO2 onsite for this purpose. According to EPA, most of the CO2 (64%) captured at industrial facilities was used in EOR activities.
CO2 is also used in the manufacturing of some kinds of food and beverages as well as in metal fabrication, fire-fighting equipment, and manufacturing of pulp and paper.
Natural gas, ethanol, and ammonia production facilities are the top three industries that capture CO2 for supplying it back into the economy.
Artificial formation of carbon-containing rocks
Limestone gets formed over a long period when calcium from a diverse range of marine life such as mollusks, foraminifera, and coral stays together and sticks into a rock formation. This way, all the carbon gets stored and converted into rocks. Now, the same process is being used to commercially produce usable products from carbon dioxide. Carbonate rocks created from CO2 can be used instead of natural limestone for some concrete mixes.
In this process, CO2 is converted to CO3 (carbonate) by mixing CO2 gas in a capture solution made with water. This results in a carbonated solution that leaves a coat of carbonate on substrate or nucleus. This is a carbonate mineral form of the synthetic limestone. This is a permanent way of sequestering captured CO2 into CO3, which can be produced in sand to gravel sizes.
How can carbon sinks be revived and restored?
Now lets look at some ways to support existing carbon sinks.
Over the last few thousands of years, the forest cover on the planet earth has been drastically reduced to create farmland, residential space and more recently for different development projects. This has impaired its capacity to absorb all the CO2 emissions that we see today. To make our forests more capable of handling global warming issues, we need to rapidly increase the forest cover.
Reforestation to make up for the depleted forest cover is an urgent need to rein in greenhouse gas effects and global warming. Besides, existing forest cover needs to be protected and rejuvenated. More managed forests where trees are grown for commercial use on a sustainable basis is also urgently called for. Instead of keeping the fields bare, it is more useful to keep them planted.
Nearly 70% of carbon on the land is stored in the soil. In this light, it makes sense to use the soil more carefully so that we don’t end up releasing the carbon from the soil without any associated benefit. Soil management is, therefore, a combination of various applications, practices, methods and treatments in the field of agriculture that enhances its health, mechanic and productivity.
We know for both agriculture and carbon storage, the topsoil is of critical importance. The soil management ensures that the carbon content in the soil remains high in the natural way. This can be achieved through proper planning of the crop, water management, and the fertilizers. There are a number of ways by which adequate soil management can be achieved. These measures include plant pest management such as crop isolation, crop rotation, tillage, planting time, mixed farming, organic soil, and mulching.
The ecosystem of a wetland makes it a more effective carbon sink than any other on the land. Of all the carbon stored in the land, wetlands account for nearly 15% while in terms of area they are only 6% of the total land mass. In recognition of its ability to sequester carbon and store it in its ecosystem, restoring wetlands should be a priority area.
Like forests, wetlands have also seen large-scale intrusion and depletion. Wetlands along the sea covered with mangroves are an important part of the marine ecosystem that also helps mitigate the effects of GHG and global warming. But, a large part of the mangrove and wetlands on which they stand in different parts of the world have been destroyed in favor of modern development and infrastructure projects. This must be reversed.
Protecting coral reefs
Coral reefs that dominate the seashore up to a depth of 30 meters are not only massive in number and proportions but they are also very effective as carbon storage systems. Coral reefs have numerous nooks and crevices that host a range of marine life. In the process, they offer a stable storage for a huge amount of carbon.
Due to rapid commercialization of the ocean resources, coral reefs are under attack from various quarters. Pollution, tourism, fishing, commercial operations of sea transport and all such activities damage the fragile ecological balance that is necessary for the maintaining and protecting the coral reef reserves.
Much like the coral reefs, seaweeds are also pervasive along the shallow waters of the sea. Seaweeds engage in photosynthesis and, therefore, absorb significant amounts of carbon dioxide from the atmosphere and release oxygen. They also host a diverse range of marine life besides playing an important role in the overall marine ecosystem.
Seaweeds are harvested for commercial use and along with other factors this is leading to imbalance and depletion of seaweeds from the sea in some of the ecologically more sensitive regions. It is important that this extremely useful carbon sink is protected and regenerated so that they can do their job more effectively and save the planet earth from GHG effects.
Carbon sinks as a mitigation for the greenhouse gas effect
Carbon sinks are an important factor that has kept global warming from going through the roof. They have absorbed significant amounts of greenhouse gases and saved the planet earth from excessive heat. However, these sinks need to be revived, rejuvenated, and restored so that they can keep working to offset the GHG emissions. The world has become more aware of their role in maintaining ecological balance in recent years. Now, this increased awareness needs to be followed up with actions.