According to so­me experts, global coal consumption is projected to incr­ease by nearly 60 per cent over the period 2005–2030 in nearly all large-scale stationary energy facilities. Coal is plentiful and is generally the least-cost option for base-load electricity generation. Every week, on an average, two new large coal power stations (each typically emitting two million tonnes of CO2 a year) are commissioned around the globe, each with an operational life of 30–40 years. They are very large investments (of the order of $1 billion), so once constructed, they lock in a pattern of emissions that are difficult to avoid. One option to keep a check on the CO2 emissions due to growth in coal-based power plants is carbon capture and storage (CCS). CCS refers to the process of capturing carbon dioxide (CO2) from large-scale emission point sources, for example, fossil fuel-powered electricity-generating stations or industrial plants, and depositing the gas in geological formations or the deep ocean for long-term storage.

The CCS technology appears to be promising. First, fossil fuels could be consumed on a large scale while emitting far fewer greenhouse gases. Second, the CCS technology can be integrated with existing electricity generation and distribution infrastructure. Third, the CCS technology has already been demonstrated to work in some applications. However, the CCS technology has also posed a number of challenges. First, the technology has yet to be deployed on a commercial basis at fossil fuel power stations. Second, it is likely to be relatively expensive and is unlikely to be adopted on a large scale, unless a significant CO2 cost penalty is introduced, particularly in relation to retrofitting existing plants. Third, it is a technology that has a relatively long time horizon before it could make a large contribution to mitigation efforts. Finally, the environmental risks of storing large quantities of CO2 in geological and ocean reservoirs have yet to be fully assessed.

CO2 capture can be done either prior to combustion or by separation from the industrial gas stream after combustion. Both pre- and post-combustion processes can remove about 85-95 per cent CO2 before it is released into the atmosphere; however, the removal process is energy intensive and thus presently costly. To a ballpark estimate, a standard coal-based power plant will consume 20–40 per cent more energy per unit of electrical output than a similar plant without the CCS. Based on the most recent IPCC analysis, the cost per unit of electricity generated from a standard coal-based plant fitted with CCS technology is expected to be 40–85 per cent higher than the same plant without CCS (this equates to a cost of $25–50 for each tonne of CO2 avoided).

Once the CO2 has been captured it needs to be transported to its storage site. There is a large variability in this cost depending upon the distance of the storage site from a power plant. For plants, which are located adjacent to a suitable storage site, the costs would be small, generally less than $1 per tonne. For distances of up to 1,000–1,500 km, pipelines are expected to be the most cost-effective option, costing approximately $10–15 per tonne of CO2 transported. Rail or road transport is technically possible, but would prove to be much more expensive than the pipeline option.

The third and final stage in the CCS is the actual long-term storage at a suitable site. The three principal storage options are: injection into suitable geological reservoirs (cost: $1–8 per tonne of CO2); storage in the deep ocean (cost: $6–30 per tonne of CO2 and still to be tried commercially); and, conversion of CO2 into stable mineral carbonates (cost: $50–100 per tonne of CO2). Thus, presently, the first option appears to be the most feasible.

The risks of leakage from well-managed geological storage sites are considered low in probability, probably less than 1 per cent over periods of up to 1,000 years where the cost of inspection and verification can be as low as $1 per tonne of CO2 stored. However, the risks of leakage from ocean storage are much more significant.

CO2 is not flammable and only becomes a health risk (from asphyxiation) when air concentrations exceed 10 per cent by volume. However, there could be local environmental hazards associated with su­dden large-scale releases, particularly from ruptured pipelines or well blow-outs. Again, with ocean storage, there are potential adverse ecological impacts. CO2 is a slightly acidic gas,

and injecting large volumes into the oceans would result in an increase in ocean acidity, which could adversely affect marine life.

The principal hurdle constraining the rollout of CCS technology is its high costs. Under best assumptions, the total estimated cost of CCS (including capture, transport, and storage) is in the range $30–70 per tonne CO2 for standard coal-based power plants. The additional cost per kilowatt hour for electricity generated by CCS-equipped plants would range from 2 to 5 cents. This would raise fossil fuel electricity costs to levels equal to or greater than several other alternative electricity-generating options, such as renewable energy. According to some studies, without a carbon-tax of at least $25–50 per tonne CO2, or the introduction of regulatory requirements for CCS technology to be fitted, CCS is unlikely to be adopted on a large scale. However, with further research into capture, transport, and storage, and “learning by doing”, the costs associated with CCS technology are expected to fall, making the technology a promising option in the future.