For some time we have been led to believe that carbon capture and storage or sequestration (CCS) is a world saviour in the abatement of climate change. Lately, the enthusiasm was softened due to the multitude of problems that must be overcome for CCS to play its expected role.
That is not to say that current expectations are not strong. On the contrary they are still substantial. Energy related carbon dioxide (CO2) emissions in 2011 reached “a record high of 31.2 gega ton (Gt)” according to the International Energy Agency’s (IEA) World Energy Outlook 2012. If the world is to avoid a long term average temperature rise of 2 degrees centigrade above pre-industrial level, CO2 concentration in the atmosphere must be limited to 450 parts per million and emissions must be reduced to about 22 Gt by 2035. For this to happen, some drastic changes in energy consumption must take place such as improving end use efficiency, saving electricity, increasing renewable energy supply and CCS. Thus CCS is supposed to contribute 4 per cent by 2020 and 17 per cent by 2035 or about 2.5 Gt.
CCS has been practised for decades by injecting CO2 in mature oil fields to increase oil production. About 30 to 50 million tonnes a year of CO2 are injected in the US oil fields. But this looks like laboratory scale compared to the size demanded for climate change abatement. The process to be meaningful must be directed at capturing CO2 from power stations where the emissions are large. The flue gas is first treated to remove sulphur oxide then CO2 is absorbed by amine solvent and then released when the amine is recovered. The CO2 is then dried and compressed to some 100 bar ready for pipeline transport and injection in saline aquifers or depleted oil fields where supposedly it will not enter the atmosphere again.
All these stages are well known and some development projects here and there are underway to improve them. But a project with all the stages at a commercial scale does not yet exist in spite of government and UN funding to encourage companies in this direction. There are other methods of capture such as converting CO2 to carbonate or producing hydrogen by partial oxidation of coal but I will limit this column to after combustion capture.
The first problem with CCS is that it will increase coal use in a power station destined for CCS by about 25 — 40 per cent to cater for the energy requirement for all the stages. This means the CCS system will have to be bigger by the same percentage to take care of the additional CO2.
CO2 in the concentration found in the atmosphere is not harmful but at very high concentration it causes asphyxiation and death. No matter how secure the design might be the risk that CO2 might leak from the storage or the pipeline into the atmosphere will still be there. The danger is well documented where a modest release of CO2 from a fire suppression system in a large warehouse caused the collapse of 14 people. In 1986, a volcanic event caused a large leakage of naturally sequestered CO2 from Lake Nyos in Cameroon and asphyxiated 1,700 people. Therefore, safe and permanent storage of CO2 cannot be guaranteed and even a modest incident may undermine its use to mitigate climate change.
For companies to pursue vigorously CCS projects, a carbon price of $60 per tonne is required to make capture and storage competitive. This may double industrial electricity prices of 6 cents per KWh and double household consumer bills.
CCS costs are not little either. Storage in saline formations or depleted oil or gas fields may cost $0.60–8.30 per tonne of CO2 injected including monitoring costs.
In 2012 the Global CCS Institute identified 75 large-scale integrated projects where 16 of these projects are in operation or in construction capturing around 36 million tonnes of CO2 a year. For example, in Algeria, the In Salah project separates CO2 from produced gas and reinjects it back in the reservoir. One million tonnes of CO2 has been captured and since 2004 and the reservoir is expected to eventually store 17 million tonnes. CO2 injection in the Sleipner gas field in Norway has been in operation since 1996 and billions of CO2 tonnes can be stored there.
About 2.8 million tonnes a year of CO2 from a coal gasification plant located in North Dakota, USA is transported by pipeline 320 kilometres across the Canadian border and injected into depleting oil fields.
These projects are nowhere near the 2.5 GT that must be stored by 2035 and considering the additional problems cited above, CCS is a long way away before it can be relied upon for climate change mitigation or abatement.
The writer is former head of the Energy Studies Department at the Opec Secretariat in Vienna.