Carbon sequestration

o Also known as carbon captureo A geo engineering technique for the long term

storage of carbon dioxide for the mitigation of global warming

o Carbon can be stored by the following ways -Terrestrial sequestration -in plants and soil - Geological sequestration – underground - Ocean sequestration – deep in ocean

About CarbonPlants and trees absorb carbon from the atmosphere by the process photosynthesis. 

Carbon is returned to the atmosphere through respiration of plants, microbes, and animals and by natural and human-induced disturbances, such as fire. 

Carbon is also released to the atmosphere as Carbon Dioxide (CO2) upon combustion of fossil fuels.

Global warming•Global warming is increase of Earth’s

average surface temperature due to a build up of green house gases in the atmosphere.• Effects of Global warming are Rising sea

level, increased temperature, Habitat damage and species affected, changes in water supply.

Green house effect

oIt is a natural process that permits the earth to retain some of the heat from the sun.

oThe energy from the sun passes through the atmosphere.

oThe gases present in the atmosphere trap energy from the sun.

oSome Infrared rays are absorbed, then emitted back to the atmosphere.

oThe greenhouse gases capture these rays and return them to the earth.

oThis energy is then used in a number of processes, including the heating of the ground surface; the melting of ice and snow and the evaporation of water; and plant photosynthesis.

Photosynthesis in mitigating CO2 levels• Photosynthesis is a natural way of recycling carbon dioxide which

helps in maintaining the CO2 level in the atmosphere. The reduction of emission alone cannot reduce the increased levels of CO2; there is a need to develop technologies for carbon dioxide capture and sequestration which helps in minimizing of greenhouse gas emission to acceptable levels.

• The process involving carbon dioxide capture and storage (CCS) is gaining attention as an alternative reducing CO2 in the atmosphere. Biological capture of CO2 using microalgae is a promising technology and has many advantages over plants.

In comparison with most of the terrestrial plants, the photosynthetic efficiency rate of microalgae is high (10-20%). The efficiency of carbon fixation through microalgae is 10 times greater than that of terrestrial plants.

Microalgae in Carbon Sequestration

• Microalgae are uni or multicellular photosynthetic organisms, either eukaryotes (green algae) or prokaryotes (cyanobacteria).• Importance of microalgae in sequestration is its

high growth rate, minimal resource requirement, high photosynthetic efficiency.

•Microalgae can tolerate • a very high concentration of CO2,

• low light intensity • saline environment

•Growth rate of microalgae is higher and has the ability of carbon fixation using solar energy•Upto 70% of the algal biomass is usable.

• Synechococcus sp. Strain PCC8806, a cyanobacterial strain is able to remove the carbon dioxide present in its growth environment either by fixation into biomass or via precipitation of CaCO3 (Carbon dioxide sequestration by Synechococcus sp. Strain PCC8806

• Synechococcus sp. Strain PCC8806, a cyanobacterial strain is able to remove the carbon dioxide present in its growth environment either by fixation into biomass or via precipitation of CaCO3 (Carbon dioxide sequestration by Synechococcus sp. Strain PCC8806

• Photosynthetic accumulation of carbon storage compounds under CO2 enrichment by the thermophilic cyanobacterium Thermosynechococcus elongatus, Jed O. Eberly and Roger l. Ely, 2012)

• Thermosynechococcus elongatus strain was able to grow on up to 20% CO2 with maximum productivity and CO2 fixation rates .