A Picturesque But Lethal Lake
Goma sits on the shore of Lake Kivu, in the Democratic Republic of the Congo (DRC). A geological anomaly containing 300 cubic kilometers of dissolved carbon dioxide and 60 cubic kilometers of poisonous hydrogen sulfide-laced methane. The gorgeous lake, tucked between the DRC and Rwanda, has the potential to explode in a rare event known as a limnic eruption, releasing these gases explosively. This may release a massive amount of heat-trapping gases into the atmosphere: the lake contains the equivalent of 2.6 gigatonnes of CO2, or approximately 5% of world yearly greenhouse-gas emissions.
Even worse, such a catastrophe might suffocate and poison millions of people by filling the surrounding valley with stifling and poisonous gas. It might be one of the worst, if not the worst, natural humanitarian disasters in human history. Hydragas Energy in North Vancouver, Canada, is currently trying to raise funds for a project to extract and use gas from the lake.
The lake is currently stable. It contains a lot of gas, but to achieve saturation point, the concentration in the location with the greatest gas would have to double. A severe earthquake or volcanic eruption, on the other hand, may cause a gas release by disturbing the stratified structure of the lake or raising gas concentrations. Some scientists are also concerned that human activities may play a role in causing an environmental crisis.
The Current Situation
Most people believe that pumping methane from the lake’s depths and burning it to generate power is both a wise use of local natural resources and a means to make the lake safer by eliminating part of its gas. This is what is currently being done. The stakes are high: methane in Lake Kivu has been projected to be worth up to US $42 billion over the next 50 years, according to experts.
However, scientists are debating on which technique of gas extraction is optimal, and whether such attempts would disrupt the lake in ways that will exacerbate rather than mitigate the hazards. Even as attempts to capture methane develop — plans are in place to increase power output by more than fivefold in the next years or decades — the controversy continues. However, scientists are debating on which technique of gas extraction is optimal, and whether such attempts would disrupt the lake in ways that will exacerbate rather than mitigate the hazards. Even as attempts to capture methane develop — plans are in place to increase power output by more than fivefold in the next years or decades — the controversy continues.
Only a few lakes in the world are considered capable of limnic eruptions, and Lake Kivu is the biggest of them. Two considerably smaller similar lakes, one in Cameroon and the other in Italy, are thousands of kilometers west.
These lakes are all located near tectonically active areas, where volcanic gases like CO2 flow upwards from deep beneath the Earth. The lakes are deep, and seasonal temperature changes do not mix the waters from top to bottom. Instead, the dissolved gas collects in the denser bottom layers, which are then sealed by a ‘cork’ of pressure from the waters above. These lakes can really explode like a champagne bottle if the gases build up to the point where bubbles develop. A drought, for example, may drop lake levels and relieve pressure on the gassy waters below; a landslide, earthquake, or lava eruption at the lake’s bottom could rearrange the water layers or provide enough heat to induce gas to bubble out.
In August 1986, the destructive potential of these lakes was demonstrated when Lake Nyos in Cameroon erupted with a boom that some people mistook for a nuclear test. More than 1,700 humans and 3,500 animals died as 1 cubic kilometer of heavier-than-air CO2 inundated low-lying areas, smothering them.
Following the explosion, to ensure this event didn’t happen again, physicist and engineer Michel Halbwachs, then at the University of Savoie in Chambéry, France, and his colleagues put a pipe into the lake from a floating pier and sucked up deep, gassy waters in 2001. This resulted in a self-powered fountain that allowed gas to vent in a miniature, controlled limnic eruption. In 2011, the team installed two more pipelines, and by 2019, Halbwachs and his colleagues believed Lake Nyos had been “completely emptied of dangerous levels of dissolved carbon dioxide.”
Halbwachs next turned his attention to Lake Monoun, which had erupted at a much lesser scale in 1984. By 2009, the lake was considered degassed after the venting pipes were constructed. Halbwach’s firm, Limnological Engineering, recently won a $5 million contract to degas CO2 from the Gulf of Kabuno, a tiny tributary of Lake Kivu with significant CO2 concentrations at shallow depths. Since 2017, the firm has been running a trial project.
Despite the potential threat that Kivu poses, there is a lot of debate over the fundamentals, such as the source of the gases, whether they are rising, and even if Lake Kivu has ever erupted. Although there are 9 brown layers in the sediments showing that mixing events have occurred in the past 2,000 years, experts have found no evidence of any violent events in the past 12,000 years that could be called limnic eruptions. Others believe there was at least one eruption 4,000 years ago, based on the evidence.
What might be surprising to many is the abundance of life within such a potentially deadly lake. The surface waters of the lake are crystal clear, and abundant with fish. Thanks to hydrothermal springs, the water temperature and salinity dramatically change around 260 meters below the surface.
Tapping The Methane
For decades, people have been extracting methane from Lake Kivu on a modest scale in order to use it for energy. However, when KivuWatt, a London-based company, launched in 2016, efforts stepped up significantly. The $200 million facility currently generates 26 megawatts (MW) of electricity, with a commitment to extend that to 100 MW. This will significantly increase Rwanda’s installed grid capacity, which is now at 200 MW.
KivuWatt’s withdrawals are currently insignificant in terms of the lake’s stock: at present extraction rates, the business will remove less than 5% of the lake’s methane in 25 years. To truly reduce the risk of limnic eruption, they need to pick up the pace of gas extraction. But as always, it’s all about supply and demand. Whilst the supply is surplus, the electricity demand just isn’t there in Rwanda yet. Around two-thirds of Rwandan households have electricity, and use on average 30 kilowatt-hours (kWh). For comparison, an average American household uses 10,649 kWh.
Benefits of Degassing
KivuWatt is a critical source of renewable base-load electricity to 2.5 million Rwandans (approximately 20% of the country’s population). The project will reduce the risks connected with the discharge of CH4 and CO2 from the lake while also providing an environmentally benign and long-term power source. It would reduce the country’s reliance on fuel for energy generation, lower electricity costs, and help the government meet its goal of 563 MW of installed power capacity by 2017.
Rwanda has a 9 percent electrification rate and 68.4 MW of installed capacity as of 2011. The KivuWatt project will supply energy to 30 community power systems. Around 200 construction jobs and 60 permanent jobs are projected to be created.
But debates around safety of gas extraction rumble on. But the only way to settle the argument about how these operations may influence the lake is to monitor if and how the density strata change. The LKMP checks the depths and inspects gas-extraction firms, and claims that its weekly profiling demonstrates that the lake is now stable.
The monetary worth of Lake Kivu, its potential explosive capability, and the wide range of ideas about how to best deal with it, continues to lead to emotionally charged discussions between stakeholders. Whilst removing gas from the lake should make it safer, there are some things that no scientist, corporation, or regulatory authority can counter or avoid, such as a volcanic explosion. We just can’t fight Mother Nature.