The New Scientist reports that a "gold rush" to extract valuable methane from the depths of lake Kivu in Rwanda may trigger an outburst of gas that could wash a deadly, suffocating blanket over the 2 million people who live around the lake's shores.
"The lake, which is almost half a kilometre deep in places, is on Rwanda's north-west border with the Democratic Republic of the Congo and contains a vast reservoir of dissolved methane. Many companies are extracting the gas to burn for electricity production, and the governments of both nations are aggressively courting further investment in extraction plants.
Now a group of biochemists warns that if unregulated extraction continues unabated, it could trigger a catastrophic outgassing of carbon dioxide - another dissolved gas abundant in the lake's depths. Such a disaster occurred at Lake Nyos in Cameroon in 1986, killing 1700 people. Kivu contains 300 times more CO2 than Nyos did, warns Alfred Wüest, a bio-geochemist based at the Swiss Federal Institute of Aquatic Science and Technology (Eawag).
Like Nyos, Lake Kivu is permanently stratified: a deep layer of dense water laden with CO2, methane, salt and nutrients is locked away beneath a surface layer of fresh water. Methane is generated by lake-bed bacteria that feed on a stream of dead algae sinking from the surface. The CO2 enters through volcanic seeps."