India has potential to store at least 395Gt of carbon dioxide

The geological formations under India have potential to store at least 395 giga-tonnes (Gt) of carbon dioxide, recent research says.

The results of the research, conducted by Dr Vikram Vishal, Yashvardhan Verma, Debanjan Chandra and Dhananjayan Ashok, all of the Department of Earth Sciences, IIT Bombay, have been published as an article titled ‘A systematic capacity assessment and classification of geologic CO2 storage systems in India’ in the latest issue of the International Journal of Greenhouse Gas Control.

“India has diverse rock formations, and we set out looking where exactly carbon dioxide could be stored,” Vishal, one of the authors, told Business Line.

Carbon dioxide capture, separation and storage have acquired utmost importance in the international goal of limiting the rise of global warming to 1.5 degrees (by 2100, over the average temperatures during 1850-1900).

Capturing carbon dioxide as it comes out in the flue gases in factories is hard enough, but, how do you dispose of it off even if you do?

Storage

Carbon dioxide can be stored permanently in saline aquifers (porous rocks holding saltwater), depleted oil and gas fields, in coal seams and basalt rocks. Each of these has a different mechanism of holding the carbon dioxide, such as adsorption, compression and mineralisation, Vishal said.

The researchers examined all the 26 sedimentary basins of India and determined that the country’s potential, across the entire landmass, holds anywhere between 395 Gt to 614 Gt of carbon dioxide. India is estimated to emit around 2.7Gt of carbon dioxide every year. (One giga-tonne is one billion tonnes.)

Coal seams are a good place to put back the CO2. Coal holds methane (also a greenhouse gas) -- hence coal-bed methane projects. But “coal has  upto ten times more affinity for CO2 than for methane,” Vishal said.

Also, basalt rocks, which essentially have silicates of elements like iron, magnesium, calcium and sodium, can easily take in CO2. The elements become their respective carbonates and remain there permanently – a mineralisation process.

Used in oil fields, CO2 can help push more oil or gas out of the ground.

Vishal said that the authors ruled that outputting CO2 into gas hydrates, an iced mixture of water and methane, was not practical with the present technology in field conditions. This contrasts with the view of some other scientists, such as Dr Rajnish Kumar of the Department of Chemical Engineering, IIT-Madras, who backs CO2 injection and storage in the abundant gas hydrate formations under the Indian seas.

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