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Tuesday 27 September 2022 09:59

Lake Kivu’s Great Gas Gamble

Lake Kivu’s Great Gas Gamble

In a first-of-its-kind endeavor, electricity-starved Rwanda and the Democratic Republic of Congo are trying to get power from a lake—and avert catastrophe.

It’s a Friday afternoon on the Rwandan side of Lake Kivu, and in what was once a quiet cove, a daring venture is taking shape

Floating just offshore, like a giant mechanical swan, is a nearly completed gas extraction platform: 3,000 tons of concrete and stainless steel that will soon begin capturing a resource not found at this scale in any other lake in the world. Dissolved within Kivu, which straddles the border of Rwanda and the Democratic Republic of Congo (DRC), are approximately 60 billion cubic meters of methane and 300 billion cubic meters of carbon dioxide. The gases, which come from nearby volcanic activity and bacteria decomposing organic material in the lake, represent both danger and economic potential.

If extracted, Kivu’s methane could be used to add up to 960 megawatts of electricity-generating capacity, more than six times what Rwanda has now. For both Rwanda and the eastern DRC, which face crippling power shortages and limited options for expanding their electric grids, that could be an economic game changer, supporting new industries and offering a chance to alleviate searing poverty. If the extraction is done properly and the countries can coöperate, it could even help improve their troubled relations and advance stability in a region long beset by turmoil.

A safety inspector examines the new barge on shore in Kibuye, Rwanda.

Just as critical, removing Kivu’s methane may prevent a possible catastrophe. With methane concentrations rising, scientists warn that Kivu will eventually experience a deadly phenomenon known as an overturn. Also known as a limnic eruption, an overturn can occur if the pressure of the gases in a lake exceeds the pressure of the water at a given depth, causing a chain reaction that releases them with violent results. Only two limnic eruptions are known to have occurred in recorded history—both in small lakes in Cameroon in the 1980s. In the deadlier of the two episodes, at Lake Nyos in 1986, more than 1,700 people were asphyxiated when a cloud of carbon dioxide, which burst from the lake along with a 100-meter fountain of water,spread as far as 25 kilometers from shore. Kivu contains a thousand times more gas than Nyos: if even part of it escaped this way, more than two million people living near its shores would be at risk.

In Kivu it’s the methane, rather than the carbon dioxide, that’s most likely to trigger a gas eruption. That adds urgency to the prospect of harnessing its energy potential, something both Rwanda and the DRC have long sought to do. After decades of little or no progress, gas extraction efforts in both countries have finally gained momentum. On my visit to the lake in February, more than a hundred orange-vested workers were putting the final touches on the first phase of KivuWatt, a $200 million project owned by the U.S. energy firm Contour Global. The lake’s first industrial-scale gas-fueled power project, it is expected to add 25 megawatts of generating capacity by the middle of this year and eventually scale up to 100. Another U.S. company, Symbion Power, is set to begin construction of a 50-megawatt project on the Rwandan side of the lake by the end of the year. In the DRC’s distant capital, Kinshasa, the Ministry of Hydrocarbons is now reviewing bids for that country’s first Kivu gas concession.

Getting the gas out correctly, however, will be tricky. Although the Rwandan government has operated a pilot gas-fired power plant at the lake since 2008, the process of extraction is novel and has been done only on a very small scale. While most experts agree that the lake’s methane should be kept from accumulating further in order to prevent a disaster by the end of the century, a few warn that certain extraction processes could disturb the natural stratification that keeps the bulk of the gases trapped in deep waters. Undertaking them could increase, rather than mitigate, the risk of gas eruption. Until a large-scale extraction operation has commenced, it also remains unclear how efficiently the technology will function and how much electricity Kivu will ultimately yield.

“We are very curious to see how our process works,” says Jarmo Gummerus, a Finnish engineer and KivuWatt’s Rwanda country manager. “Very soon we’ll have a much better idea of the potential of this lake.”

Boosting the grid

Three hours by car over winding roads from KivuWatt, the Rwandan capital, Kigali, does not appear to be a city in the midst of an energy crisis. In the 21 years since the Rwandan genocide, in which an estimated 800,000 people were killed, the city of a million has transformed from a corpse-ridden backwater into a tidy modern metropolis. Today, Kigali is a town of smooth tree-lined streets, sprouting office towers and American-style subdivisions that stretch to the surrounding hills. It’s also the engine of a Rwandan economy that’s grown at an average of 8 percent per year over the last decade—one of the highest rates in the world.

As Rwanda and its capital have developed, however, the country’s electricity grid has struggled to keep pace. Although installed capacity has doubled in the last five years, it remains a scant 156 megawatts. Today, nearly 80 percent of Rwanda’s 12 million people, including the vast majority of rural residents, still lack a connection to the grid. Families and business that do have power, meanwhile, face some of the highest electricity prices in the region—in part because nearly a third of the country’s power is generated from imported diesel and heavy fuel oil, which arrive by truck from Kenya and Tanzania. According to the World Bank, Rwandan companies pay an average of 24 cents per kilowatt-hour, compared with 15 cents in Kenya and 17 cents in Uganda. The average industrial user in the United States pays less than seven cents.Advertisement.

Kivu, 1,460 meters above sea level, is part of a system of lakes along the Great Rift Valley.

Hoping to reduce its widespread poverty and boost its small industrial base, Rwanda has set ambitious electrification targets. The country’s second Economic Development and Poverty Reduction Strategy, launched in 2013, assumed a nearly fourfold expansion of the power grid, to 563 megawatts, by the end of 2017. Given financial constraints and limited domestic energy resources, however, this will be difficult to pull off. Aside from KivuWatt, the only significant power project nearing completion is a 15-megawatt plant that will burn peat. Although work has begun on another 80-megawatt peat facility, and financing is being arranged for two large-scale regional hydroelectric projects, it’s not clear if any will be on the grid by the 2017 target. Rwanda might also have significant geothermal resources, if preliminary surveys are correct, but two exploratory wells drilled in 2013 came up empty. And although Rwanda recently inaugurated East Africa’s first utility–scale solar field and authorities are working to bring off-grid solar installations to rural homes, schools, and hospitals, it’s unlikely that solar will be able to meet a significant portion of industry’s demands. Out of desperation, Rwanda could soon become a significant electricity importer. According to the Ministry of Infrastructure, arrangements are in the works to purchase 30 megawatts from Kenya this year and, eventually, up to 400 megawatts from Ethiopia.

Across the border in the eastern part of the Democratic Republic of Congo (formerly known as Zaire), the power crisis is even more acute. The DRC, a country of 77 million people in a territory roughly the size of Western Europe, contains extensive hydroelectric resources. If fully tapped, the Congo River’s Inga Falls could yield an estimated 40,000 megawatts, nearly twice the capacity of the world’s largest power station, the Three Gorges Dam in China. Today, however, the DRC’s aging grid has an installed capacity of just 2,400 megawatts, roughly half of which is routinely unavailable because the transmission infrastructure is in such poor shape. In the war-torn east, power is particularly limited. Goma, the largest city on Lake Kivu, has an available capacity of less than five megawatts—a meager amount for a town of a million residents and a situation, some argue, that helps promote conflict. If boosting eastern Congo’s grid can spur the development of industries, says Bantu Lukambo, an environmental activist based in Goma, that would reduce the appeal of the region’s dozens of armed groups, which are magnets for youth with no other employment prospects. In addition, he says, more development could weaken the market for illicit charcoal, a trade that generates millions of dollars per year for local militias and leads to extensive deforestation.

Gases from the lake will enter the gray stainless-steel tube to be separated.

The volcanoes responsible for much of Kivu’s gas loom over Goma and its environs. In 2002, an eruption of Nyiragongo, a volcano located 20 kilometers north of town, destroyed a fifth of the city, leaving tens of thousands of people homeless and depositing lava that’s still being used as a building material. On a drive west from town, Mathieu Yalire, chief geochemist at the government-run Goma Volcano Observatory, shows me several depressions known to contain lethal seepages of carbon dioxide that are concentrated near the ground at the edges of past lava flows and occasionally asphyxiate children. At Kasinga Primary School in the town of Sake, 25 kilometers west of Goma, principal Batchoka Lubungo shows us a photo, displayed on the wall of his office, of a young victim.

“One morning we found the boy dead over there,” he says, pointing to a known danger zone just outside his window. “We keep this picture here as a warning to the students.”

The presence of mazuku is a reminder of Lake Kivu’s potential to sow disaster. But the carbon dioxide is not the only danger. The lake’s geochemistry is unusual, largely as a consequence of local subaquatic springs that absorb carbon dioxide from the region’s volcanic soil and feed the gas into Kivu’s deepest waters. Much of the methane comes from decomposing organic matter; the rest comes either from the volcanic soil or from bacteria converting the carbon dioxide to methane. Critically, these springs are saline, while the water sources feeding the lake’s upper layers are fresh. Since saline water is much denser than fresh water, this creates density gradients that prevent the gases from diffusing upward and into the atmosphere. Although this stratification is stable at present, the gas accumulation it makes possible has apparently led to limnic eruptions in the distant past. If nothing is done, it is likely to do so in the future.

Top: Women dry tiny sambaza, or sardines.
Bottom: A sign in Kibuye explains KivuWatt.

Still, much about this risk remains uncertain. Studies of Kivu’s sediment record suggest that the lake has experienced at least five overturns in the last 6,000 years. It’s not clear, however, whether these events involved all the lake’s layers of water, thus releasing all its gas, or just portions of its upper layers. In addition, though recent measurements have found that the concentration of methane is increasing—at a rate that could bring the gas close to saturation by the end of the century—it’s not yet known why this is happening or whether it will continue. Complicating matters, Kivu consists of five different basins of varying depths, each with distinct physiochemical properties.

It is clear, though, that an eruption in Kivu’s main basin could cause a disaster of apocalyptic proportions. If all the methane and carbon dioxide currently dissolved in Kivu were released into the atmosphere, they would cover the entire lake in a cloud of gas more than 100 meters thick. If even a small fraction of the gas were to get out, it could suffocate entire towns along the lake shore. This can happen if water at a given depth becomes fully saturated with gas and is lifted by a big earthquake, a volcanic eruption, or another external disturbance to a depth where the water pressure is not great enough to keep the gas dissolved. |

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