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Perhaps because of the lack of alternatives, the most commonly discussed solution to the 
problem of disposing of carbon dioxide is to pump the gas underground - a technique 
known as ‘geosequestration’. In this system, the CO2, for example, could be pumped into 
underground pockets within depleted oil wells, or disused coal tunnels. This carries, 
however, three serious disadvantages, namely: the risk of leaks, the considerable costs 
involved, and finally, the unproven effectiveness. Let us look at those three disadvantages 
in detail. 
Firstly, there is the risk of leaks. Although the gas would be deep and sealed over by 
masses of rock and earth, the huge pressures in these spaces would turn the gas into a 
liquid stale, capable of moving through rock fissures or faults. This could allow the gas to 
eventually be released to the surface. Since CO2 is heavier than air, and thus pushes 
oxygen aside, such leaks could result in the suffocation of thousands, or tens of thousands 
of people — certainly not a consequence to be taken lightly. Natural CO2 leakage from 
volcanic build-up has already witnessed such deadly events. 
The other problem of geosequestration is the cost. The time and effort spent on materials 
and construction, primarily the pipeworkthrough which the gas would travel, does not 
come cheaply. So, if this system were to be implemented in, say, coal-tired power plants, 
the extra cost would have to be paid by the electricity user, whose bills would almost 
double as a consequence. Few people are prepared to pay this much simply to make a 
small dent on the effects of global warming. And this leads to the final problem. 
The most basic question is whether geosequestration actually reduces global warming. 
The problem here is that the energy needed to create and drive the sequestration process 
would require approximately a quarter of a coal-fired electricity plant's output. In other 
words, the plant would have to burn one quarter more of its coal just to account for the 
sequestration of the carbon dioxide, and with coal producing other noxious pollutants, 
such as sulphur, ash, and heavy metals, the environment is hardly benefited at all. 
Nevertheless, there are many active experimental efforts underway, primarily in oil 
production sites. These are small but intensively monitored and analysed. All we can say 
now is that the jury is still out on whether underground carbon storage will one day be 
feasible.