Science and Technology

Carbon dioxide to methane: TIFR develops a simple solution

M Ramesh | Updated on May 09, 2021


Besides cutting the greenhouse gas, the method’s use of magnesium makes it ideal for producing rocket fuel on Mars

Converting carbon dioxide, a problematic greenhouse gas, into useful fuels has been the holy grail of the scientific community for some years now.

The latest among the many pathways that scientists have come up with is from the Tata Institute of Fundamental Research (TIFR), the simplicity of which almost makes it look like some mumbo-jumbo. Mix carbon dioxide, water and magnesium, at room temperature and pressure, and lo and behold! you get methane, methanol, formic acid and some hydrogen.

Wow! How does this happen?

A paper by Vivek Polshettiwar, the leader of the team that developed the process,

in Chemical Science, published by the Royal Society of Chemistry, describes it step by step.

It is a nine-step mechanism, in which you get hydrogen in the first step, formic acid in the fourth, methanol in the sixth and methane in the last step. One can, of course, stop at methanol too.

Magnesium, an abundantly available metal, sells for ₹1,000-2,000 a kg. Polshettiwar’s paper says a kg of magnesium can produce 2.43 litres of methane, 940 litres of hydrogen and 3.85 kg of basic magnesium carbonate. Polshettiwar told Quantum that you could recover the magnesium, but you don’t have to. Magnesium carbonate is also an industrial product, used in the production of green cement and in the pharma industry.

Magnesium can be reacted with water to get hydrogen, but in the absence of carbon dioxide the hydrogen yield is extremely low — 2.24 litres per kg of magnesium. This is because the surface of the metal reacts with water and forms a layer of magnesium hydroxide.

Since magnesium hydroxide is not soluble in water, the layer prevents sub-surface magnesium from reacting with water. However, in the presence of carbon dioxide, the magnesium hydroxide immediately gets converted into carbonates, which are soluble in water, exposing more magnesium to water for more reactions.

The entire production of 940 litres of hydrogen takes just under a quarter of an hour, at room temperature, atmospheric pressure. Polshettiwar says the process is “exceptionally simple and safe”.

Is it economically viable? Polshettiwar says this is “the cheapest of any other reported carbon dioxide conversion protocols in the literature to date”, but notes that the methane or hydrogen is not cheaper than those produced from fossil fuels. But this is a pathway to use up carbon dioxide.

Made-in-Mars methane

Polshettiwar points to an interesting application of this process.

Currently, the world is grappling with ways to make fuels on Mars to fire a return journey to Earth. With this process, you can make methane on Mars. Methane is a rocket fuel.

Mars’s atmosphere is almost entirely comprised of carbon dioxide. The planet has water in the form of ice. Its soil contains an abundance of magnesium. There you are — you have all the three ingredients to make methane. Polshettiwar’s ‘magnesium-assisted carbon dioxide conversion at low temperature’ process cues “a step towards magnesium civilisation on Mars”.

Of course, more work is needed. Polshettiwar experimented at 26.5 degrees Celsius. The average temperature on Mars is minus 63 degrees Celsius. One has to see how the process works in cold. If it works better, it is a jackpot for Mars exploration.

Published on May 09, 2021

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