carbon sequestration

Carbon sequestration can be defined as the capture and secure storage of carbon from the atmosphere on a long term basis. In other words, C sequestration can be defined as net removal of atmospheric COinto long-lived pools such as terrestrial and oceans by the photosynthetic pathway of plants and micro-organisms. The main objective of the carbon sequestration is to reduce the atmospheric CO2 concentration to reduce the impact of climate change of global warming.

The balance between C additions of photosynthetic plant products to the soil and their losses via their subsequent decomposition and microbial respiration determines the amount of organic C present in the soil. Plant residues, manure, sewage sludge, and other organic C by-products are the major sources of C inputs in the terrestrial ecosystem.

Types of Carbon Sequestration

Above ground biomass carbon sequestration

The above ground biomass includes plant, animals, and litter from these. The proportion of carbon stored in these materials varies widely depending upon the species. In general, plants fix the carbon by consumption of COthrough the photosynthesis mechanism. In this atmospheric carbon is converted in to plant biomass and retained within it until it decays. Woods of trees contain about 25-48 percent by carbon based on its dry weight. So forest has a huge potential in carbon sequestration.

Approaches for above ground biomass carbon sequestration

  • Sustaining the forest cover
  • Decreasing deforestation
  • Regeneration of natural forests
  • Establishing tree plantations and agroforestry.
  • Improving management of agricultural soils and rangelands
  • Improve the fertilizer use efficiency
  • Improving the diet of ruminants

Below ground Carbon Sequestration

Below ground carbon sequestration includes carbon fixation by soil, soil microbes, etc. Carbon stocks in soil exceed the carbon stocks in the vegetation by a factor of two to five. The global soil holds twice as much as the atmosphere (1400-1500 Gt C). The soil carbon pool comprises two components. Soil and vegetation in together exchange 100 GT C per year. In India, the amount of carbon stored in the soil is 23.4-27.1 Gt which is 1.6-1.8% of the global reserve.

Soil Carbon sequestration

It generally refers to the medium and long term (10-15 years) storage of C in the terrestrial soil ecosystem through various physical, chemical biochemical and biological processes in soils. Soils have the capacity to accommodate a substantial amount of C from the atmosphere by photosynthesis and sequester it for a long. The soils have an inherent upper limit or “C saturation level” above which no additional C can be stored. The process controlling saturation limit can be modified and controlled to the soil C sink and the time period over which the soil can be exploited for C sequestration.

Mechanism of Soil carbon Sequestration

Physical Carbon Sequestration

In this soil organic carbon (SOC) is held with soil mineral matrix and aggregates which inhibit microbes accessibility and their enzymes. Secondly, SOC is adsorbed into the clay surfaces which is also not reachable by microbes. The penetration of SOC into interlayer spaces also does the same.

Chemical protection and stabilization mechanisms

In this mechanism, the SOC is converted into a nondegradable carbon material through various chemical processes such as charcoal burning and humification, etc.

Biological protection and stabilization mechanisms

Biological organism improves the soil aggregate formation and hence stabilizes the SOC indirectly. Certain microbial products are highly resistant to the degradation, E.g., Glomalin protein of VAM

Approaches for Soil Carbon Sequestration

  1. Restoration of degraded soils
  2. Improved management of grassland and forest soils
  3. Minimum or conservation tillage
  4. Water conservation
  5. Residue and manure management
  6. Mulching practices
  7. Management for reducing soil erosion

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