Rwanda is converting methane gas, known to erupt from the depths of volcanic lakes with deadly consequences, into electricity that powers nearby businesses, creates jobs, and may help avert future eruptions.
Located on the border between Rwanda and the Democratic Republic of Congo, the 1,040-square-mile Lake Kivu is considered a killer lake, Power Magazine reported.
It sits in a volcanic region of the western Great Rift Valley, where its deep bottom waters absorb high concentrations of carbon dioxide from magma-heated springs underground. Microbes convert much of the CO2 to methane. The dissolved gas is trapped in solution under pressure at the bottom of the lake but can emerge to the surface in large quantities — a process known as a limnic eruption, or “overturn.”
Because the region often has seismic activity and volcanic discharge, Lake Kivu is known to have violent overturns. Geologists believe they happen at Lake Kivu about every 1,000 years and another one is due, Power Magazine reported.
Similar eruptions of toxic gas occurred at much smaller lakes in Cameroon — Lake Monoun 1984 and Lake Nyos in 1986 — killing more than 1,700 people by suffocation. An overturn at Kivu could be catastrophic and endanger millions of lives on both sides of the border because it contains far more dissolved gases than those two lakes, experts say.
Some locals say Kivu has already claimed lives, Reuters reported.
“There are stories based on superstition that swimmers are taken away by demons,” said Eric Manywa, 20, who sometimes swims in the lake. “I don’t believe that. It might be due to methane gas.”
Rwanda wants to provide 70 percent of the country’s 11 million population with power from the grid or off the grid by 2018, up from 25 percent now. Much of it will come from renewable resources.
Rwanda’s KivuWatt plant opened in May, developed by U.S. company ContourGlobal. Jarmo Gummerus is country manager for the plant on the shores of Lake Kivu, where a hi-tech barge collects methane from the depths.
The gas in the lake contains combustible methane – extracted for the power plant – mixed with other gas that is highly toxic, Gummerus said. “It just kills almost immediately so it’s very dangerous.”
The gas can cause death by suffocation if it gets into contact with people because it displaces oxygen needed for breathing, said Ivan Twagireshema, a Rwandan scientist and energy extraction expert, SciDevNet reported.
“We don’t know to what extent Kivu’s eruption risks can be, but it’s important we mitigate the risk of gas eruption before it’s too late,” Twagireshema said.
There is an urgent need to degas the lake, a prospect both Rwanda and the DRC have long considered, said Germaine Kamayirese, Rwanda’s state minister for energy, water and sanitation.
Gummerus, a Finnish engineer, oversees KivuWatt, a US$200 million project by Contour Global, which was contracted by Rwanda government to conduct Phase 1 of the gas extraction.
Extraction began Sept. 1 and will be done in two phases over 25 years.
The government of the DRC is negotiating with an independent firm to extract the gas.
Nearly 80 percent of Rwanda’s 12 million people lack access to electricity, and business people who can afford or access power pay the highest electricity prices in East Africa, according to World Bank data.
About a third of Rwanda’s power comes from diesel and fuel oil imported through Kenya and Tanzania at high cost, Twagireshema said.
Rwanda’s first methane-extracting and power-producing plant, a 3-megawatt pilot project, started operating in 2008, Power Magazine reported.
Since then, the government has negotiated more methane gas concessions. In 2008, U.S.-based ContourGlobal entered into a partnership with the Rwandan government to transform the lake’s gas deposits into a 25-megawatt power plant — KivuWatt. ContourGlobal owns about 4,000 megawatts of capacity in 20 countries.
Financial backers for the KivuWatt project include African Development Bank, the Emerging Africa Infrastructure Fund, the Netherlands Development Finance Co., and the Belgian Investment Co. for Developing Countries, Power magazine reported. In 2011, ContourGlobal contracted Finnish energy technology firm Wärtsilä to supply an engine-based plant with engineering, procurement, and construction.
The plant relies on two processes: methane extraction and power production. Gas extraction is performed on a barge anchored 13 kilometers (8 miles) offshore in Lake Kivu. Gas-rich water is raised from 300 meters (984 feet) below and the pressure is reduced, with gas bubbles extracted from the water. Raw gas is then washed in four wash towers, according to ContourGlobal.
The clean gas is then transported to the power plant via pipeline, where three engines, optimized to run on Lake Kivu’s gas, use it as fuel. The engines have a lower heating value than standard natural gas. “This has helped to downsize the size of the extracting barge and optimize the costs of producing electricity,” ContourGlobal said in a statement.
The design and technology is performing “even better than expected,” according to ContourGlobal. The gas extraction facility is expected to support an additional 9 megawatts of power generation by the end of 2016.
ContourGlobal works with the local population, training and developing local workers to run KivuWatt and future installations. DRC is also considering a similar project, the government said.
Rwanda is planning a second phase that will involve two or three barges to generate an additional 75 megawatts, Power Magazine reported.
KivuWatt plant is already benefiting local businesses in the region of rolling green hills and volcanic peaks, which the government wants to promote as a tourist destination, Reuters reported.
“When I built this hotel in 2013, we could have power cuts every three hours, at least, but nowadays we have electricity 24/7,” said Jerome Musomandera, owner of the Kivu Plaza Hotel, one of a number of hotels next to the lake.
Some other hotels said they had yet to feel the benefit, but hope they will soon be able to unplug private stand-by generators and enjoy lower bills from grid power.
As it adds more supply, state-run Rwanda Energy Group wants to lower tariffs to help the poor and support industry, said CEO Jean Bosco Mugiraneza.
Rwanda charges 17 U.S. cents per kilowatt hour for industry and 21 cents for others.
The average price people in the U.S. pay for electricity is about 12 cents per kilowatt-hour, NPR reported.
Rwanda’s installed power capacity is now 190 megawatts. By the end of July that’s expected to increase to 205 megawatts after a new peat-burning plant is linked up. The aim is 583 megawatts by 2018.
KivuWatt was a pioneer in Rwanda, according to Reuters. It represented the country’s first private power purchase agreement, and helped pave the way for others.
