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The Mystery on Lake Kivu
Nature’s Fizzy Energy Drink
After a 10 year hiatus, I found myself back in (on) the Dead Sea this summer. Undoubtedly, one of the strangest bodies of water in the world. The beauty on the surface hides the unique chemistry secrets below - and keeps me floating above.
I thought the Dead Sea would hold the top spot in my list of “WTF Science” travels…but I would be wrong. We will come back to why very shortly…
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The 1960’s American TV show ‘The Beverly Hillbillies’ famously starts off with Jed Clampett seeing hydrocarbon (oil) emerging from his property. As the iconic theme song lyrics go: “And then one day he was shootin at some food, And up through the ground come a-bubblin’ crude”.
Between the US TV shows like Hillbillies and Dallas, all of this talk of oil. But what about a-bubblin’ gas? Maybe a 2020’s, “climate-sensitive” TV reboot would use a transition fuel like gas instead of oil? But, is it even possible that we could get this to occur naturally, gas seeping from the ground that we could capture?
Well, look no further than Africa’s own gem: Lake Kivu.
Lake Kivu lies on the border between the Democratic Republic of the Congo (DRC) and Rwanda, sitting above a tectonically-active region flanked by two volcanoes to the north: Mount Nyiragongo and Mount Nyamuragira. These volcanoes are some of the most active in the world, with a recent 2021 eruption of Mount Nyiragongo forcing the evacuation of nearly 500,000 people from the nearby town of Goma (Volcanic Eruption).
Deep within the lake at depths up to 480 meters, ~10 TCF (or, 10,000,000,000,000 ft3) of dissolved carbon dioxide (CO2) has seeped into the waters from the volcanic rock underneath. This geothermal activity also keeps the deep waters warm, with a temperature of 26°C (79°F). Unlike almost every other (non-frozen) lake, the seafloor temperature is similar - or warmer - to the surface temperature of 24°C (75°F).
Additionally, and important for this story, 2 TCF (2,000,000,000,000 ft3) of methane (CH4) is also trapped in the deep, a result of organic matter degradation via interaction with the CO2 in the warm waters. Of note, the dissolved gases (CO2 / CH4) do not mix along the water column, remaining trapped in the deeper sections (>300m) in a ‘stable stratification’ The shallower sections remain fresh and ripe with fish.
Fun Fact: Lake Kivu is the largest lake in Africa that does not have a single hippopotamus or crocodile. So, for all my friends afraid of being attacked by the Loch Ness Monster or a vicious whale shark - you are safe here.
Ticking Time Bomb?
As CO2 continues to seep into the waters, accompanied by continued degradation of bio-materials resulting in CH4 generation, the dissolved gas concentrations may be slowly increasing (the scientific community has shown mixed results related to key concentration variance over time).
In the event that the concentrations increase such that the partial pressures of these gases become greater than the pressure of the water column (~450 psi at depth), the gas may begin to evolve. Critical concentrations may be computed via Henry’s Law:
P = k * C (where P = partial pressure, k = Henry’s Law constant for each gas species, and C = concentration).
Once the concentration increases beyond the critical partial pressure, a dangerous situation, knowing as a limnic eruption, could occur. A limnic eruption (“lake overturn”) is a rare event in which the gases evolve (“erupt”), forming a gas cloud capable of asphyxiating all living things in the vicinity. Additionally, the sudden rise of CO2 from the deeper water could trigger flooding, as the evolved gas bubbles displaces the shallower fresh water, pushing this upwards as a pseudo-tsunami towards the shoreline.
The instances of limnic eruption are rare, with only a handful of known events. In 1986, more than 1,000 people died when Lake Nyos (Cameroon) released a cloud of CO2 that suffocated entire villages and surrounding livestock.
For Lake Kivu, the impact of a limnic eruption would be catastrophic. Not only is the lake much larger than the other known eruption sources (~1700x the size of Lake Nyos), the surrounding population (~2 million) in the area is also significantly higher. Add to this the potential for ignition from the CH4 and the results could be even more dire.
Rwanda: Where Environmentalism Meets Pragmatism
While perhaps not an imminent threat, the safe and effective management of the dissolved gases within Lake Kivu represents a prudent consideration for the surrounding communities. However, there is also the understanding that a 2 TCF methane gas “reservoir” - one that does not require further exploration and/or drilling - is a potentially valuable resource for the local communities.
Again, hydrocarbon production from lakes are not rare, with the most famous example likely being Lake Maracaibo (Venezuela). But, that involves drilling conventional production wells from the lake surface. What IS rare - and unique in the world for Lake Kivu - is that the hydrocarbon here is IN the water itself. Could this resource be harnessed with a limited footprint? Border country Rwanda thinks so.
Landlocked with no proven hydrocarbon reserves and a growing economy, Rwanda has embraced a diverse mix of solutions to address their own energy needs. Per the US Agency for International Development (USAID), approximately 50% of the installed generation capacity (~210 MW) is via hydroelectric power, with the balance coming heavily from renewable sources such as solar. These investments have led to a significant reduction in cost of electricity production.
With a stated goal to increase access to electricity to 100% of the population by 2025, additional (and affordable) options are being considered. The government of Rwanda continues to prioritize investment in energy infrastructure, including expanding the national grid and increasing capacity of existing plants.
In 2019, a $400MM deal between the Rwanda Development Board (RDB) and Gasmeth Energy was struck to extract and process the methane reserves in Lake Kivu. At the time, RDB Chief Executive Officer, Clare Akamanzi, noted:
“Natural gas is the most environmentally friendly fossil fuel. The natural gas produced by the plant will help reduce the use of wood and charcoal as a cooking fuel as well as diesel fuel in the automotive industry.
The deep water of Lake Kivu contains dissolved methane and carbon dioxide. These gases pose a serious risk to all the oxygen dependent life in the vicinity of the lake as they continue to build up. However, methane gas also provides an energy resource valued at billions of dollars for the Kivu region.
We therefore welcome the Gasmeth Energy project because not only will it reduce the risk of a methane gas explosion, it will also provide jobs, reduce Rwanda’s natural gas import bill, increase gas exports and provide cleaner cooking fuel for Rwandans”
How will this be accomplished? In 2012, the BBC generated this fairly high-level schematic of the technology. Using “straws” to draw up the gas-saturated deep waters, the gases are extracted from the water and sent via pipeline to shore, where they are converted to power (or compressed natural gas, CNG, as the case for the Gasmeth project).
The process on Lake Kivu involves a similar method:
Dissolved gas-rich waters are drawn up to the surface via piping conduits to offshore floating barges.
As the water ascends and the pressure is reduced, the gas begins to evolve (a very similar process to what scuba divers experience, where gas expansion can lead to ‘the bends’).
At the surface, the gas is recovered and sent through extraction membranes to purify the methane (CH4) and remove/capture the carbon dioxide (CO2).
CO2 is re-injected back into the lake waters, while the CH4 is sent to shore via pipeline.
Onshore, the methane is converted into compressed natural gas (CNG)
The project was successfully commissioned and hooked-up of the the Shema Power Lake Kivu (SPLK) methane plant in early 2023. Currently operating at ~37.5 MW, the facility plans to expand to 56 MW in 2024.
Subsequent to Rwanda’s steps to extract methane, additional projects have been undertaken on Lake Kivu. Most recently, the Democratic Republic of Congo (DRC) commissioned US-based Symbion Power to develop a similar gas-to-power project on the north side of Lake Kivu
Despite the novelty of the application, the gas-to-power project on Lake Kivu has many similarities to traditional hydrocarbon production that may benefit from shared lessons learned:
“Reservoir” Surveillance - one of the key aspects of the project’s long-term success will be careful monitoring and surveillance of the lake waters. Similar to a traditional (subterranean) reservoir, understanding compositional changes over field life and how differences may impact the “topsides” process will be critical. The extraction process could disturb the lake’s layers and may increase the risk of gas eruption. To avoid this risk, “tank models” may be used to predict the acceptable depths to extract and release the deep water.
Environmental - as the composition of the lake could change over time, careful consideration of the impact on the lake’s ecosystem must be accounted for. The deep water contains much more nutrients than the surface water and releasing it into the surface could have catastrophic consequences for the biodiversity, from algae to fish. Nutrients could generate a high production of algae that deteriorate the water quality and the food chain. Understanding ecological impact and any overboard discharge requirements are critical.
Production Chemistry - with a relatively high pH (8.6), the surface waters contain a high concentration of dissolved minerals. As a result rocks around the shores are generally covered in a mineral scale. While not an issue for the gas-to-power production, monitoring changes in water chemistry and CO2 (acid gas) levels will be an ongoing balance. At least there are no hydrate concerns (due to warm water temperature…the hydrate formation temperature at-depth is ~35°F)
By expanding the electricity generation of the country, Rwanda is continuing a global trend of increasing access to energy. Rwanda’s success in providing affordable electricity to its citizens has had a significant impact on the country’s economy and social development.
Moreover, households have been able to access electricity for lighting, cooking, and powering appliances, which has improved their quality of life. CNG has replaced traditional fuels such as diesel, peat, coal and wood.
Pontem Power (?)
Embracing the ethos of ‘All Energy is Good Energy’, perhaps its time to consider Pontem Power. As the world moves towards a more electrified future, the importance of ‘gas-to-power’ and similar projects will only increase. In the United States alone, $3.5B was approved recently (Oct ‘23), focusing on strengthening electric grid reliance.
And developing novel technologies that can harness our natural resources in the most cost-efficient and environmentally-conscious ways will demand all of us to think outside the box.
Similar to ‘The Mystery on Lake Kivu’, Pontem Power may be a little too Scooby-Doo, despite being on-brand with our other Pontem verticals. Perhaps we should lean into more conventional names, taking from the likes of market-leaders such as NRG, GE, AES, or LS Power. Hmm, TG Power has a nice ring to it….
Either way, as we expand offerings within the energy space - particularly within emerging markets such as Africa - projects like those in Lake Kivu will become more common and undoubtedly uncover new challenges to be solved. We look forward to collaborating with our partners in these areas and bringing affordable energy to all.
Drawing inspiration from the US version of ‘The Office’ (“Threat Level Midnight” episode): “I bet you're wondering why do I know so much about Lake Kivu. Well because I AM Lake Kivu”. I’m off to go for a swim in those non-croc infested waters…
To learn more about the science beyond Lake Kivu, check out some of these interesting articles:
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