Carbon capture and global warming

Human activities often result in emissions of carbon dioxide. Often, in order to stop or reduce the emissions we have no option but to stop or reduce the activity itself. For example, if somebody is using a wood-fired cook-stove, she can shift to a gas-fired stove to reduce emissions.

However, in some cases, the emitted carbon dioxide can be ‘captured’, so that the gas doesn’t rise up in the atmosphere and cause (further) global warming. For example, it is possible to collect the fumes coming out of the chimneys of coal-fired power plants and ‘box’ them up. ‘Carbon capture’ refers to the techniques used to gather carbon dioxide emissions and put them away so that they don’t cause harm.

There are essentially two ways of approaching carbon capture and storage, or CCS. One, technology-based solutions and, two, nature-based solutions — though when people speak of CCS, they usually refer to the first. Technology solutions entail putting up machinery to capture fumes (such as from factories, large engines, etc) and removing carbon dioxide from them. The next step is, of course, to figure out a way of disposing of the carbon dioxide.

The most basic way to do this is to bury the gas underground — in pores of sedimentary rock formations, or in dead oilfields, that is, in sands that once held oil or gas, or in underground coal seams.

This works if you don’t have to transport the carbon dioxide over large distances to the burial ground. The captured carbon dioxide could be injected into living oil and gas wells so as to push out the hydrocarbons.

Scientists have also suggested that the carbon dioxide could also be injected into gas hydrates (frozen gas-water mixture), whereupon the carbon dioxide will push out the gas in the hydrate and take its place.

Nature-based solutions do not ‘capture’ carbon dioxide but offset the emissions by sucking up the gas from the atmosphere — whether these should really come under ‘carbon capture and storage’ is a moot question. Nature-based solutions essentially involve growing trees. Mangroves are said to have an enormous potential to suck up carbon dioxide and are, therefore, in the limelight today.

If done on the scale required, it would definitely help reduce global warming. In 2019 (the pre-pandemic year), the world emitted 36.7 billion tonnes of carbon dioxide. Today, CCS projects are negligible in comparison with the emissions.

The earliest CCS projects are believed to be Sleipner and Snovhit projects in Norway, which have captured and sequestered about 24 million tonnes of carbon dioxide in their 23 years of operations. In 2014, the Boundary Dam project in Canada was built to capture and bury around six million tonnes of carbon dioxide a year, but the project has been experiencing some problems.

A few more projects have come up since then. According to the Global CCS Institute as of 2018, there were 43 large-scale facilities — 18 in commercial operation, five under construction and 20 in various stages of development.

CCS is costly. Typically, if you want to do CCS in a thermal power project, the process would take away between 6 per cent and 10 per cent of the power generation for itself. Then, there are capital and maintenance costs. Until now, there was no great urgency to do CCS projects.

The government’s own plans are more in the realm of ‘nature-based solutions’. It is very difficult to see technology CCS coming up in India, unless financially supported by the developed countries.

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