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Capture it,shut it,forget it

As long as the world continues to run on carbon-based fuels,CO2 emissions will be a worry. Countries are now experimenting on capturing this CO2 and storing it away. But there are concerns too....

In an ideal situation,the Copenhagen climate talks would have been a success and the world free of fossil fuels. But this isn’t an ideal world and to get rid of fossil fuels here would be just wishful thinking.

As long as the world continues to be dependent on carbon-based fuels,we will keep emitting carbon dioxide (CO2) and other greenhouse gases into the earth’s atmosphere with disastrous effects. How about a technology then that captures this CO2 and stores it away for good? Wishful thinking? Not quite. Nations are now taking a serious look at technology that will help harness fossil fuels while significantly reducing CO2 emissions with technology like CO2 capture and geological storage (CCS),or CO2 sequestration.

What is CCS?

This is a process by which CO2 is captured from gases produced by the combustion of fossil fuels or industrial processes,and is compressed,transported and injected into deep geological formations for permanent storage. CCS also involves processes where CO2 is stripped from a product to meet consumer specifications.

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CAPTURE: In the first stage,CO2 is isolated and captured,either before or after fossil fuels are combusted. For instance,in natural gas production,CO2 is removed from the gas stream to meet quality standards. In steel and cement production,the idea is to use post-combustion,pre-combustion or oxy-fuel combustion approaches. Ideally,the capture technique has to be tailored for the process involved.

TRANSPORTATION: In the second stage,the separated CO2 is compressed and transported to storage sites or reused for industrial purposes. CO2 is already being transported by road tankers and pipelines for use in industrial applications or to increase production in depleting oil and gas fields. However,the scale required for CCS will call for new infrastructure.

STORAGE: The final stage sees CO2 injected into and contained within subterranean geological structures,often below depths of one kilometre. As CO2 is present at these depths in a stable form,the chances of it escaping are negligible. Appropriate storage sites include depleted oil or gas fields or deep porous saline aquifers with impermeable rock above them. This ‘rock seal’ prevents CO2 from returning to the surface. Once injected,a range of sensing technology is applied to monitor the sites.

Researchers from around the world are working on the Otway Project in Australia’s south-western Victoria to develop and implement a rigorous monitoring and verification programme that complements the demonstration of the subsurface geosequestration technology. The project is also leading the way in defining regulatory requirements for geosequestration. About 100,000 tonnes of the greenhouse gas carbon dioxide will be injected and stored deep underground as part of the project.

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However,the prohibitive costs of capturing and storing CO2 have meant that while many projects have been announced,very few have progressed to an implementation stage. The four CCS projects currently underway have successfully stored millions of tonnes of CO2,but the total amount stored per year is less than what would be emitted by a medium-scale coal fired power plant.

Pushing for the worldwide development and adoption of CCS technologies is the Canberra-based Global CCS Institute,a multinational initiative formed earlier this year. Founding members of the institute,including India,agreed to work together to jointly promote CCS. “The institute is currently undertaking a comprehensive audit of CCS projects underway across the world. Once the audit is over,we will provide a suggested approach on how to overcome deployment gaps,” says Dale Seymour,Global CCS Institute’s senior vice-president.

The government of Australia too is throwing its weight behind the technology. Harinder Sidhu,Chief Adviser (International) of Australia’s Department of Climate Change,thinks only CCS can deal with the extent of the climate problem and help achieve targets. “As long as we are dependent on coal or other fossil fuel-based power,carbon capture seems to be the only answer. With so much sunken infrastructure,it will take longer for a country like Australia to completely shift to cleaner fuels,” she says.

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India is among the countries looking at the commercial adoption of CCS. In fact,there is a proposal to consider the Badarpur power plant in Delhi for the application of CCS technology. ONGC,too,is working with Norwegian oil and gas major StatoilHydro ASA to develop CO2 management projects. Recently,the PSU initiated a project by which CO2 generated during the processing of sour gas at its Hazira plant in Gujarat is to be captured and transported to nearby Ankleshwar where it will be used to enhance oil recovery from the depleted reservoir.

Is it safe?

There have been concerns about whether the large-scale transportation and storage of CO2 will be safe. In 1986,a large leakage of naturally sequestered carbon dioxide rose from Lake Nyos in Cameroon and asphyxiated 1,700 people. This incident has been raised by many as evidence for the potentially catastrophic effects of sequestering carbon. However,no incidents have yet been reported from the decade-old Sleipner gas field in Norway,the oldest plant that stores CO2 on an industrial scale. Studies in Canada have suggested that the likelihood of stored CO2 release is less than one per cent in 5,000 years.

First published on: 20-12-2009 at 21:16 IST
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