In 1986 a large leakage of naturally sequestered carbon dioxide rose from Lake Nyos (external - login to view)
in Cameroon (external - login to view)
and asphyxiated 1,700 people. While the carbon had been sequestered naturally, some point to the event as evidence for the potentially catastrophic effects of sequestering carbon artificially. (external - login to view)
The Lake Nyos disaster resulted from a volcanic event, which very suddenly released as much as a cubic kilometre of CO2 gas from a pool of naturally occurring CO2 under the lake in a deep narrow valley. The location of this pool of CO2 is not a place where man can inject or store CO2, and this pool was not known about nor monitored until after the occurrence of the natural disaster.
The use of CCS can reduce CO2 emissions from the stacks of coal power plants by 85-90% or more, but it has no effect on CO2 emissions due to the mining and transport of coal. It will actually "increase such emissions and of air pollutants per unit of net delivered power and will increase all ecological, land-use, air-pollution, and water-pollution impacts from coal mining, transport, and processing, because the CCS system requires 25% more energy, thus 25% more coal combustion, than does a system without CCS". (external - login to view)
Another concern regards the permanence of storage schemes. It is claimed that safe and permanent storage of CO2 cannot be guaranteed and that even very low leakage rates could undermine any climate mitigation effect. (external - login to view)
The IPCC concludes, however,, that the proportion of CO2 retained in appropriately selected and managed geological reservoirs is very likely to exceed 99% over 100 years and is likely to exceed 99% over 1,000 years. (external - login to view)
Finally, there is the issue of cost. Greenpeace (external - login to view)
claims that CCS could lead to a doubling of plant costs. (external - login to view)
CCS though may remain economically attractive in comparison to other forms of low carbon electricity generation. (external - login to view)
It is also claimed by opponents to CCS that money spent on CCS will divert investments away from other solutions to climate change.
IPCC has provided estimates of air emissions from various CCS plant designs (see table below). While CO2 is drastically reduced though never completely captured, emissions of air pollutants increase significantly, generally due to the energy penalty of capture. Hence, the use of CCS entails a reduction in air quality.
Carbon capture and storage - Wikipedia, the free encyclopedia (external - login to view)