Sequester CO2 and produce Natural Gas

Sequester CO2 and produce Natural Gas

Subject – Environment

Context – IIT-Madras professor finds a way to tackle climate change while, at the same time, secure our energy requirement

Concept –

• The professor has shown it is possible to first separate carbon dioxide, in an almost pure form, from the flue gases of industries, particularly coal-fired thermal plants.
• The next step is to inject the carbon dioxide into the gas hydrate zones, whereupon the carbon dioxide molecules push out the resident methane molecules and take their place. The methane can be tapped off.
• Hydrates are a mixture of water and a gas, defined as “a solid, ice-like form of water that contains gas molecules in its molecular cavities”.
• For separating carbon dioxide from flue gases— cool it to 1.5 degrees Centigrade and pressurise it to 30 bars, and let it react with water. Carbon dioxide will separate out to form carbon dioxide hydrates.
• Next, if you depressurise the chamber, (nearly) pure carbon dioxide will separate from the hydrates.
• India has mind-boggling amounts of natural gas in the form of hydrates — of the order of 2,000 trillion cubic feet. The Krishna-Godavari basin alone has about 134 tcft.
• Methane is the best among all fossil fuels — far better than coal. Carbon dioxide capture and storage is a costly affair.
• In a coal-fired thermal power plant, it could take up 25 per cent of the power produced by the plant.
• Methane mined from gas hydrates can pay for it. But, importantly, the net carbon dioxide emission will be less than the unabated emissions from thermal plants.
• The conventional way of carbon capture and sequestration has been through the use of chemicals called amines. The problem here is that you have to spend a lot of energy to recover the amines. In contrast, separating carbon dioxide from carbon dioxide hydrates costs practically nothing.