Lake Kivu is filled with carbon dioxide and methane at its bottom layer to the extent that it could explode at any moment, threatening the lives of 2 million people living around the lake.
Lake Kivu is surrounded by towering cliffs, nestled within the valley that crosses Rwanda and the Democratic Republic of the Congo. On the lake, fishermen often navigate with small boats and catch fish.
Lake Kivu is a geological anomaly. The deep waters beneath this stratified lake are saturated with carbon dioxide and methane. Only two other lakes exhibit similar characteristics: Lake Nyos and Lake Monoun, both of which erupted in the last 50 years, releasing toxic gas clouds that suffocated any human or animal in their path. When Lake Nyos erupted in 1986, it caused nearly 2,000 deaths and wiped out four villages in Cameroon. Alarmingly, Lake Kivu is 50 times longer than Lake Nyos and over twice as deep. Millions of people live along its shores.
To address this threat and convert the gases in the lake into fuel, the Rwandan government has licensed a private company, KivuWatt, to extract methane from the lake and use it for the national power grid. However, some researchers warn that this effort could impact the lake’s structure, triggering an eruption. They propose safer alternatives to dilute the methane in the lake, but extraction is likely to be more costly and challenging over time.
Lake Kivu in Africa. (Photo: Africa Adventure).
The Process of Lake Kivu Becoming a “Ticking Time Bomb”
Lake Kivu is located along the East African Rift Valley, with several hot springs scattered around supplying carbon dioxide and methane to its deep waters. “Lake Kivu has a complex vertical structure”, explains Sergei Katsev, a lake researcher at the University of Minnesota Duluth. “While the upper layer (60 m) mixes frequently, the rest of the lake is stratified. Nearly 300 km3 of carbon dioxide and 58 km3 of methane are dissolved along with toxic hydrogen sulfide, still trapped at the bottom of the lake. They are located 259 m below the water surface.”
“These gases could explode above the water. When the lake reaches 100% saturation (currently over 60%), it will erupt immediately”, says Philip Morkel, an engineer and founder of Hydragas Energy, an organization seeking funding for a project to extract methane from the lake for electricity production. “It is like a quiet boiling kettle until it starts to bubble. The lake could also erupt if the water layers are disturbed, such as by earthquakes or extensive lava flows.” Just outside the rift area directly beneath the lake, there are two active volcanoes within a 24 km radius.
A potential eruption of Lake Kivu would be catastrophic. According to Morkel, the lake would release between 2 to 6 gigatons of carbon into the atmosphere in a single day. For comparison, the total global carbon emissions currently amount to approximately 38 gigatons per year. The released gas would linger above the lake in a fog cloud for several days to weeks. Creatures around the lake at the time of the eruption would perish due to the extremely toxic gases. Anyone caught in the cloud would die within just one minute.
Rwanda’s Efforts to Manage Lake Kivu and Extract Fuel
Lake Kivu straddles the border between Rwanda and Congo. (Photo: AFP).
Confronted with this looming disaster, the Rwandan government has allowed KivuWatt to extract methane from the lake and convert it into energy. “The mechanism is relatively simple”, explains Martin Schmid, an expert at the Swiss Institute of Water and Environmental Research. “You take water from a certain depth rich in gases, then separate the water from carbon dioxide and methane. Next, the degassed water is pumped back into the lake. So far, KivuWatt has supplied 26 MW of energy from the lake to Rwanda’s power grid, which currently has a total capacity of 300 MW.”
However, some experts argue that the current efforts to remove gases from the lake could trigger an eruption. “If you pump water back into the deep layers of the lake, you dilute the resource area for the future. But if you pump it from a higher elevation as KivuWatt is doing, the water will sink through the dense water layers, causing vertical mixing. The eruption risk is linked to this vertical movement,” Katsev notes.
While scientists can monitor the amount of gas trapped in the lake, estimating the risk of an explosion, many unpredictable factors could trigger an eruption. For example, earthquakes or sudden lava could stir up the water layers in the lake, causing an explosion. The risk may also arise from efforts to pump methane from the lake. Methane extraction began on the Rwandan side in 2016, aimed at reducing the risk of an explosion while providing energy to the national grid. However, some experts warn that this disturbs the lake’s structure, potentially triggering an explosion instead of preventing it.
