Project KivuWatt: Turning an explosion risk into a power source
02 May 2012
Naturally occurring methane was discovered in Rwanda's Lake Kivu in 1936, as researchers attempted to understand why it was home to so few fish. Now, a New York-based company is steering a project to develop methane-powered generating capacity on the shores of the lake
Lake Kivu is in a highly volcanic area and much of the CO2 enters the lake from the volcanic rock beneath, with bacteria deep in the lake transforming the CO2 into methane
The lake is located at an altitude of 1,462m, is 485m deep and has a surface area of 2,400 sq.km. In 1976, studies determined it contained approximately 250-300 cu.km. of dissolved carbon dioxide and 55-60 cu.km. of methane gas – both trapped at significant depth and continuing to increase on a daily basis.
Lake Kivu is a highly volcanic area and much of the CO2 enters the lake from the volcanic rock beneath, with bacteria deep in the lake transforming the CO2 into methane over time.
Scientists estimate Lake Kivu contains around 1,000 times more gas than the two Cameroonian lakes, Lake Monoun and Lake Nyos, which both erupted in the 1980s. In 1984 gas from Lake Monoum killed 37 people, while two years later an eruption at Lake Nyos suffocated 1,700 people and 3,500 livestock in nearby towns and villages.
The dissolved gases are kept in the water by the high pressure at such depths. The higher the pressure, the more gas can be dissolved in the water. Landslides and volcanic events are thought to change the density of the gas in the water at depth, causing eruptions to bubble to the surface.
In Lake Kivu the gas saturation of the deep water is now so high that if the lake is disturbed, a huge gas eruption may be in store with unthinkable consequences for the two million people who live around its shores.
The project includes barge-mounted gas extraction and treatment facilities, submerged floating gas pipelines and an onshore gas receiving facility
If the build-up of CO2 is a concern, so too is the presence of methane, which could ignite once exposed to the air given the numerous possible ignition sources around and on the lake, including fishing boats.
Project KivuWatt, which is being led by New York-based ContourGlobal, will develop the methane resources contained in the lake and, at the same time, reduce the risk of a potentially serious environmental incident.
In the project’s first phase, processed methane will power three gas engine generator sets to produce approximately 25 MW of electricity for the local grid. Phase 2 is expected to add another 75 MW of capacity, employing nine additional sets to expand KivuWatt to 100 MW of power for Rwanda’s citizens.
The gas production facility will include: a platform- or barge-mounted gas extraction and treatment facility for every 25 MW of power capacity, a submerged, floating pipeline to transport the fuel gas ashore from each barge and an onshore gas receiving facility.
Rwanda’s level of electrification is very low, and the economy currently only has access to very expensive liquid fuels. By tapping the indigenous methane, Project KivuWatt will play a significant role in advancing the country’s development and improving its socio-economic prospects. The full realisation of Phase 2 also could provide the potential for exporting electricity to neighboring countries, according to ContourGlobal, with Uganda as the most likely purchaser.
The first barge is located eight miles from the shore, and has already lowered four risers to the gas-rich layers 350m below
The first barge is located eight miles from the shore, and has already lowered four risers to the gas-rich layers 350m below. If all goes to plan, there should be four barges or platforms on the lake when methane production is at its planned maximum.
The methane will be piped to the Rwandan shore, where it will be used to fuel a new power plant. The CO2, however, will be reinjected into the lake, partly to avoid releasing a greenhouse gas, and partly because it is less of a risk without the methane.
But there are risks. Environmental consultants Sinclair Knight Merz, who reviewed the KivuWatt plans, warned that if it was not carefully operated, it could itself cause an explosion or gas release from the lake.
Engineer Augusta Umutoni, who leads the Rwandan government team monitoring the project, rejects this, but does worry that the extraction process could change the lake's chemistry. The surface water could become more acidic, she says, or lead to a growth of algae which could be bad news for Kivu's fish and the human communities that depend on them.
This is why the project will start off on a small scale, with the methane extraction pilot phase later in 2012 closely monitored for its effects on the lake and biosphere.
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