CONTROLLING CARBON DIOXIDE
Fossil fuels are all derived from trees and vegetation that grew millions of years ago and subsequently became buried beneath the surface of the earth. Without man’s intervention the carbon contained in these materials would have remained buried and removed from the carbon cycle. As a result of human activity they have been returned to the carbon cycle.
An immediate cessation of all combustion of fossil fuel would stabilize the situation. That is currently impossible. Too much global economic activity depends on burning coal and gas. As the figures in Table 1.2 showed, predic- tions suggest that the use of fossil fuels, particularly coal, will increase over the next decades, not decrease. The popular strategy in some regions of switching fuel from coal to gas reduces the amount of carbon dioxide generated but does not eliminate it.
One short-term measure would be to capture the carbon dioxide produced by a combustion power station and store, or sequester, it in a way that would pre- vent it from ever entering the atmosphere. Technologies exist that are capable of capturing the carbon dioxide from the flue gas of a power plant, and these are being developed for commercial deployment. Finding somewhere to store it poses a more difficult problem.
One solution is to pump it into exhausted oil and gas fields. There are other underground strata in which it might be stored. A third possibility is to store it at the bottom of the world’s oceans. The enormous pressures found there would solidify the gas and the solid would remain isolated unless disturbed. Whether this would be environmentally acceptable is another matter.
These solutions are all expensive and none is particularly attractive. How- ever, they may become necessary as short-term solutions. Over the longer term the replacement of fossil fuels with either renewable technologies that do not rely on combustion or with biomass-generated fuel that releases carbon dioxide when burned but absorbs it again when it is regrown, will be necessary if conditions are to be stabilized. That appears likely to take most of the coming century, at least.