Methane in Lake Kivu
Friday, 17. August 2007, 09:36:16
Lake Kivu is the westernmost and most elevated (1,460m above sea level) of the string of rift lakes which curves through east-central Africa (“Africa's Great Lakes”). It has a surface area of about 2400 km2 and a maximum depth just under 500 m. It lies on the border of the the Democratic republic of Congo and Rwanda.
Is Lake Kivu a Time Bomb Or Source of Energy?
The total water volume of the lake is 580 km3. Density stratification of the water column severely restricts vertical mixing. Research has shown the lake's deep waters contain an estimated 65 km3 of methane. Studies show the amount of methane gas and carbon dioxide in the bottom of Lake Kivu has increased by 30 percent in the last 30 years. In an interesting study published 34 years ago in the journal Science of 6 July 1973, titled “Methane in Lake Kivu: New Data Bearing on Its Origin” the total amount of methane in the lake was estimated at about 50 km3. This study considered a volcanic origin of the methane very unlikely, and the authors suggest that most of the methane was formed by bacterial production from abiogenetic substrates of carbon dioxide and hydrogen.
According to Prof Boniface Kaningini, director-general of the university college Institut Superieur Pedagogique de Bukavu (ISO-Bukavu) and a biologist with at least 20 years of research on Lake Kivu, the origin of the methane gas on the lake goes back 40 years ago when the sardine Limnothrissa miodon – locally known as Ndakala was introduced into Lake Kivu from Lake Tanganyika (Irrin News of 5 August 2007). The Swiss Federal Institute of Aquatic Science and Technology (Eawag) concluded that the "the introduction of Limnothrissa miodon, the first pelagic and planktivore fish in Lake Kivu, could be responsible for significant changes in the nutrient fluxes".
An article in New Scientist (of March 2003) describes how methane from the lake could power entire Rwanda. The gas reserve should be enough to supply Rwanda's electricity needs for 400 years. Apart from providing electric power for much of Rwanda, the tapping of the gas would help revive devastated forests and quell the danger of a natural disaster.
In February 2006 BBC reported that The Rwandan government has signed an $80m deal with an international consortium, Dane Associates, to start exploiting the methane. The technology required is already available, and a brewery next to Lake Kivu has used methane from a pilot plant to power its boilers for more than two decades (since the 1980s).
The Lake may also be a natural hazard. According to lake water experts a potentially catastrophic event called a ‘limnic eruption’ could occur if volcanic or landslide activity caused the lake waters to turn over and release the gases from the bottom of the lake. A cloud of released gases would smother all lakeside life. The only two known and observed ‘limnic eruptions’ are at Lake Monoun in Cameroon in 1984, killing 37 people; and more catastrophically in 1986, nearby Lake Nyos. At Lake Nyos, over 80 million cubic metres of carbon dioxide were released from the lake depths into the atmosphere. (Limni is a greek word for lake)
Lake Kivu, Lake Nyos and Lake Monoun are termed as "Africa's Killer Lakes" in a 2006 UN Environmental Programme (UNEP) report. It said Lake Kivu remains a cause for "serious concern" as approximately two million people live in the lake basin.
Whatever the source of the methane, scientists agree the solution is to tap the gas as an energy source rather than risk a possible disaster.
Is Lake Kivu a Time Bomb Or Source of Energy?
The total water volume of the lake is 580 km3. Density stratification of the water column severely restricts vertical mixing. Research has shown the lake's deep waters contain an estimated 65 km3 of methane. Studies show the amount of methane gas and carbon dioxide in the bottom of Lake Kivu has increased by 30 percent in the last 30 years. In an interesting study published 34 years ago in the journal Science of 6 July 1973, titled “Methane in Lake Kivu: New Data Bearing on Its Origin” the total amount of methane in the lake was estimated at about 50 km3. This study considered a volcanic origin of the methane very unlikely, and the authors suggest that most of the methane was formed by bacterial production from abiogenetic substrates of carbon dioxide and hydrogen.According to Prof Boniface Kaningini, director-general of the university college Institut Superieur Pedagogique de Bukavu (ISO-Bukavu) and a biologist with at least 20 years of research on Lake Kivu, the origin of the methane gas on the lake goes back 40 years ago when the sardine Limnothrissa miodon – locally known as Ndakala was introduced into Lake Kivu from Lake Tanganyika (Irrin News of 5 August 2007). The Swiss Federal Institute of Aquatic Science and Technology (Eawag) concluded that the "the introduction of Limnothrissa miodon, the first pelagic and planktivore fish in Lake Kivu, could be responsible for significant changes in the nutrient fluxes".
An article in New Scientist (of March 2003) describes how methane from the lake could power entire Rwanda. The gas reserve should be enough to supply Rwanda's electricity needs for 400 years. Apart from providing electric power for much of Rwanda, the tapping of the gas would help revive devastated forests and quell the danger of a natural disaster.
In February 2006 BBC reported that The Rwandan government has signed an $80m deal with an international consortium, Dane Associates, to start exploiting the methane. The technology required is already available, and a brewery next to Lake Kivu has used methane from a pilot plant to power its boilers for more than two decades (since the 1980s).
The Lake may also be a natural hazard. According to lake water experts a potentially catastrophic event called a ‘limnic eruption’ could occur if volcanic or landslide activity caused the lake waters to turn over and release the gases from the bottom of the lake. A cloud of released gases would smother all lakeside life. The only two known and observed ‘limnic eruptions’ are at Lake Monoun in Cameroon in 1984, killing 37 people; and more catastrophically in 1986, nearby Lake Nyos. At Lake Nyos, over 80 million cubic metres of carbon dioxide were released from the lake depths into the atmosphere. (Limni is a greek word for lake)
Lake Kivu, Lake Nyos and Lake Monoun are termed as "Africa's Killer Lakes" in a 2006 UN Environmental Programme (UNEP) report. It said Lake Kivu remains a cause for "serious concern" as approximately two million people live in the lake basin.
Whatever the source of the methane, scientists agree the solution is to tap the gas as an energy source rather than risk a possible disaster.
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http://allafrica.com/stories/200708150332.html
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http://news.bbc.co.uk/2/hi/africa/4698278.stm
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http://www.afromusing.com/blog/2007/05/03/methane-gas-from-lake-kivu-rwanda/
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http://www.newscientist.com/article.ns?id=dn3438
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http://perso.orange.fr/mhalb/kivu/eg/eg_1a_lac.htm
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http://www.irinnews.org/report.aspx?ReportId=73738
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