Wednesday, November 30, 2011

Lake Kivu in Africa in Danger of Exploding

Lava hitting Lake Kivu in January 2002 from the nearby erupting Nyiragongo volcano. Photo courtesy: bbcnews

The Rwandan government has a plan to reduce the risk of a lake erupting while at the same time producing energy.

Deep below the surface of Lake Kivu lies a major threat to the two million people who live around the perimeter.

At the bottom of the lake are dissolved gases including 256 cubic kilometres of carbon dioxide and 65 cubic kilometres of methane, meaning the lake could explode if provoked, reports BBC.

Lake Kivu, which is a shared resource between Rwanda and the Democratic Republic of Congo, is in a volcanic area and the CO2 enters the lake from the volcanic rock. The methane is created when bacteria in the lake mixes with CO2. The dangerous gases are kept at bay because they are deep below the surface and at high pressure, but if the lake is shaken, such as by an earthquake, the water would shoot upwards.

Photo courtesy: bbcnews

"Think of it like a bottle of fizzy drink," said Professor Brian Moss of the University of Liverpool to BBC. "The carbon dioxide has been dissolved in the drink. As long as it's under pressure, it doesn't bubble. But when you take the top off the bottle, the drink fizzes because you've reduced the pressure, and the gas is able to come out."

The presence of methane is even more of a concern than the build-up of CO2, because methane could ignite when exposed to air.

"The methane would not spontaneously cause an explosion on the surface." said Professor Robert Hecky from the Large Lakes Observatory at the University of Minnesota to BBC. "(But,) there are numerous possible ignition sources above and around the lake."

What people around Lake Kivu fear happened to two Cameroonian lakes in the 1980s. More than 1,000 people died in 1986 when one of the lakes released a cloud of CO2 that suffocated entire villages.

To decrease the impact if the lake does erupt, the Rwandan government has a plan to extract the dissolved gases from the lower levels of the lake.

ContourGlobal, the New York-based firm developing the project, will use what are basically four big straws to suck up water from the saturated zone. The methane will be separated and pumped ashore to a power plant and the water and CO2 will go back into the lake. The methane will be burned to generate energy.

Not only will this make the lake much safer, but Rwanda will be able to rely less on foreign fuel. Right now almost half of the country's electricity is generated from diesel fuel, which is imported.

However, the plan can be quite dangerous. Environmental consultants Sinclair Knight Merz told BBC if it is not done carefully, it could cause an explosion. They also fear the water may become more acidic and that would be bad news for the fish and the people who depend on it.

A pilot project is expected to start producing energy later this year.

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