Carbon sequestration refers to the process of removing carbon from the atmosphere and depositing it in a reservoir. In simple language, Carbon Sequestration encompasses all forms of carbon storage such as oceans, plants, soil and underground geologic formations. On this basis, Carbon sequestration is of three types as follows:
Terrestrial Carbon Sequestration
- Indirect sequestration whereby ecosystems (e.g., forests, agricultural lands, and wetlands) are maintained, enhanced or manipulated to increase their ability to store carbon.
Geologic Carbon Sequestration
- CO2 can be stored, including oil reservoirs, gas reservoirs, unminable coal seams, saline formations and shale formations with high organic content.
- These formations have provided natural storage for crude oil, natural gas, brine and CO2 over millions of years. Geologic sequestration techniques would take advantage of these natural storage capacities.
Ocean Carbon Sequestration
- Oceans absorb, release and store large amounts of CO2 from the atmosphere.
- There are two approaches for oceanic carbon sequestration which take advantage of the oceans’ natural processes. One approach is to enhance the productivity of ocean biological systems (e.g., algae) through fertilization. Another approach is to inject CO2 into the deep ocean.
Soil Carbon and Carbon sequestration
Soil carbon refers to the carbon held within the soil, mainly as organic content. Soil carbon is the largest terrestrial pool of carbon ( around 2,200 Gigatonnes). Soil carbon plays a key role in the carbon cycle and thus is important in global climate models. It has been shown that 1kg of carbon released from the soil constitutes 3.64kg of Co2 in the atmosphere.
The exchange of carbon between soils and the atmosphere is a significant part of the world carbon cycle, which is extensive both spatially and temporally. Carbon, as it relates to the organic matter of soils, is a major component of soil and catchment health.
With reference to Carbon sequestration, the soil is one of the largest reservoirs, where carbon could be restored.
What are the Farming Practices that help in Carbon sequestration?
- Mulching →because it helps to retain moisture and organic matter
- Zero Tillage → Does not help directly in carbon sequestration but helps in stopping release of soil Carbon
- Crop Rotation → Helps by increasing soil organic content, so foster Carbon sequestration
- Strip Cropping and Contour Bunding → Increase carbon inputs so help in carbon sequestration
- Switching from Field to Tree crops → Helps to retain carbon and nutrients in soil
- Rotational Grazing and Pasture Management
- Intercropping
Can Organic Farming help in Carbon Sequestration?
Organic Farming is supportive for Carbon Sequestration. One example is Organic Mulch. Organic mulch is basically a type of compost made from decaying plants or trees. It can be one of the ways of sequestering carbon. Organic mulching refers to covering the soil with any organic matter such as applying compost or farm yard manure over the soil surface followed by adding a layer of dry organic matter over it.
Here, the compost contains an array of beneficial microbes, where the dry matter is rich in carbon and the green matter is rich in nitrogenous substances. When decomposition of these components takes place the carbon nitrogen ratio in the soil becomes 10:1, ideal for the proliferation of microbes.
How dumping of Iron can Induce Carbon Sequestration?
Dumping of Iron to the upper ocean can significantly induce the Carbon sequestration in Oceans. This is because introduction of iron to the upper ocean will stimulate phytoplankton bloom. This is due to a phenomena called “Iron fertilization”, whereby introduction of iron to the upper ocean to stimulate a phytoplankton bloom is adopted. Like all plants, phytoplankton takes up C02from air and converts it to carbon compounds like carbohydrates. The plant quickly dies and starts sinking, taking the carbon with it. What happens thereafter is the key to the technique’s efficacy: If it sinks well below the ocean surface, the carbon would effectively have been put away for a long period (Carbon sequestration). This has led to several experiments in recent times.