An Introduction to CO2 Capture and Storage

It has become increasingly clear that reduction of the emissions of carbon dioxide arising from combustion of fossil fuels is needed. Replacement of fossil fuels for other energy sources and measures to reduce the primary energy demand are important paths of achieving this goal. A third path, which is beginning to receive recognition, is the capture and storage of the carbon dioxide formed from the combustion or conversion of fossil fuels. The purpose of this symposium is to give an overview of the status of the technology for capture and storage, and to highlight related work carried out in the Nordic countries. Below an introduction to the CO2 problem and to the status of CO2 sequestration is given. The CO2 problem The latest IPCC evaluation concludes that the temperature increase during the last century was 0.6±0.2oC (IPCC, 2001), and that it is "likely that, in the Northern Hemisphere, the 1990s was the warmest decade and 1998 the warmest year" during the last 1000 years. (However, "…less is known about annual averages prior to 1,000 years before present and for conditions prevailing in most of the Southern Hemisphere prior to 1861.") The estimated temperatures during the last thousand years are shown in Fig. 1. Although it would be difficult to prove, it is very likely that the noted temperature increase has been caused by the emission of greenhouse gases, of which CO2 released from fossil fuel combustion is the primary one. Today the concentration of CO2 in the atmosphere is about 370 ppm, which is 30% higher than the pre-industrial level of 280 ppm. The stabilisation of the CO2 level at twice the pre-industrial level, or 550 ppm, is estimated to require a gradual reduction of the average CO2 emissions per capita by a factor of two before the year 2100, see Fig. 2. The corresponding reduction in Europe would have to be much greater because of the higher emissions per capita, about 10 ton/year. Even with such measures the climate is expected to be dramatically affected, with an estimated average temperature rise of 1.5-4.5 degrees. These numbers are put in perspective by a comparison: the average world temperature during the last ice age was approximately 4 degrees lower than today. Although many uncertainties remain regarding greenhouse gas effects, it is clear that even a temperature increase of a few degrees would have enormous