Lake Kivu is a scenic lake situated in Rwanda, Africa near the border with the Democratic Republic of Congo. Over two million people live on its shores and depend on fish from the lake for their food source. However, the lake itself is a ticking time bomb. A thousand feet underneath the surface lies massive amounts of dissolved gas- approximately 265 cubic kilometers of carbon dioxide and 65 cubic kilometers of methane (keep in mind that one cubic kilometer is 400 times the size of the Great Pyramid of Giza). 

The carbon dioxide comes from volcanic activity at the bottom of the lake. Combined with the low levels of light and oxygen-free environment, this creates the perfect ecosystem for bacteria that convert carbon dioxide to methane, leading to unusually high concentrations of both of these gases. The enormous pressures at those depths keep the gases dissolved in the water, but the saturation is getting to the point where a disturbance, such as an earthquake or landslide, can cause what is known as a limnic eruption.

A limnic eruption, also called a lake overturn, is similar to shaking up a bottle of soda and releasing the cap. All of the pressure is released, so the dissolved carbon dioxide fizzes out and explodes out of the bottle. The same thing happens in lakes with immense amounts of dissolved gas, just at a catastrophic level. Not only does the water shoot straight up out of the lake, but carbon dioxide clouds are released. Since carbon dioxide is more dense than air, it hugs the ground as it moves outward from the lake, essentially smothering and suffocating anyone living near the explosion.

This occurrence is not something straight out of a science fiction novel- it has actually happened in relatively recent history. In August of 1986, Lake Nyos, a small lake formed on top of a volcanic crater in Cameroon, underwent a limnic eruption. An estimated 1.6 million tons of carbon dioxide were released that moved at over 60 miles per hour into the surrounding area. 1,746 people and 3,500 livestock were almost instantly killed as the gas cloud deprived them of oxygen.

If the events at Lake Nyos seem horrific, a similar eruption at Lake Kivu would be even more deadly. Not only is Lake Kivu 3,000 times larger than Lake Nyos, but it contains 350 times more dissolved gas, and studies show that the gas concentrations are only increasing with time. More importantly, however, is the fact that the shores of Lake Kivu are densely populated with over 2 million people. If an eruption were to happen, it would occur so fast that all of these people would likely be killed on the spot without any warning.

Clearly, something needs to be done to minimize limnic eruption risks. At Lake Nyos, scientists found a way to install a tube that slowly releases carbon dioxide from the water into the air. However, things get a little more complicated in Lake Kivu because it also contains methane, a very valuable gas for energy production. Thus, scientists want to try to find a way to capture the methane, which would be an enormous economic boost for the country, while also minimizing the risk of eruption. The solution they came up with included a floating platform that would suspend a tube deep down into the water. Using pressure differences, they would get the water to start bubbling and drive the gases out of the lake. Since methane is less soluble in water than carbon dioxide, it would come out first and could be captured.

While this sounds like a good idea, there are a few major problems. Many scientists are wary to even attempt to extract the gas in the first place, because too much disruption can cause the lake to explode, which is what they are trying to prevent. There is also disagreement about what to do with the carbon dioxide. Some think that it should be removed from the water to reduce the risk of future eruptions, but others argue that there should be as little interference as possible so the extraction itself does not cause a disaster. On top of this, there are conflicts of interest because some of the scientists who started studying the dangers of Lake Kivu are now working on extracting methane for a profit.

Lake Kivu certainly provides an interesting conundrum between safety and profit, since extracting the gas could make the area more safe and benefit the local economy but could also trigger the lake to erupt itself. As Rwanda has become more politically stable in the past few years, more and more businesses are looking to work with the government to capture the methane. A month ago, Rwanda signed a $400 million deal to produce bottled gas from Lake Kivu, in hopes that the gas can be provided cheaply to the Rwanda citizens who currently rely on burning wood and coal for electricity. Hopefully the extraction will go well and lead to the disarming of one of Africa’s killer lakes.