Published on June 15th, 2019 | by David Zarembka0
Mining Methane In Lake Kivu, Rwanda: An Unusual Source Of Renewable Energy
June 15th, 2019 by David Zarembka
KivuWatt, a 34 MW power plant in Kibuye, Rwanda, was conceived to help reduce the risk of an overpressure gas outburst at Lake Kivu. The first-of-its-kind integrated methane gas extraction and production facility has since become a critical regional producer of power.
On August 15, 1984, Lake Monoun in the Cameroon exploded in an inversion eruption called a limnic (a great word to remember for your next Scrabble game). This resulted in the release of a large amount of carbon dioxide that asphyxiated 37 people. Two years later on August 21, 1986, another limnic eruption occurred on Lake Nyos, also in Cameroon. This disaster killed 1746 people and over 3500 livestock. Only 4 people survived by somehow having the presence of mind to run uphill. What happened?
In certain lakes in volcanic regions, the bottoms of lakes become saturated with carbon dioxide, which is heavier than water. Then a precipitating event such as an earthquake or rockslide disturbs the layers of water and the CO2 at the bottom erupts to the surface. Lake Monoun and Lake Nyos now have naturally bubbling “tubes” that bring the CO2 to the surface much like when you open a can of soda and the CO2 bubbles up.
In order for the CO2 not to saturate Lake Monoun and Lake Nyos again, scientists developed a method to bring the CO2 to the surface by using a pipe. Since the gas bubbles up like the CO2 in a soda, the gas shoots a fountain of water sometimes over 150 feet high. A number of these pipes have been installed in each of the lakes. See a photo of such a solution (CO2 degassing pipe) from George W. Kling in Lake Nyos here
Lake Kivu, between Rwanda and the Democratic Republic of the Congo (called “DRC” by Africanists), is many times larger than the two Camerooning lakes. It is the eighth largest lake in Africa, with a surface area of about 1040 square miles. Two million people live on its shores.
There is evidence that about a thousand years ago Lake Kivu had a limnic explosion. Due to volcanic activity, not only is there a large concentration of CO2 in the bottom of the lake, but in addition bacteria are converting some of this CO2 to methane. If the lake had a limnic event, people would die from CO2 suffocation, but the methane could also explode and set off a tremendous fire. If this were to ever happen, it could be one of the largest natural disasters in the world in terms of the number of people killed.
Mount Nyiragongo it 20 miles north of Lake Kivu in the DRC. It has erupted 34 times since 1882. There was a massive eruption of Nyiragongo in January 2002 and its lava flowed all the way into Lake Kivu. There were fears that the lava might set off a limnic explosion. Luckily, it didn’t.
This danger led the Rwanda government to explore the idea of mining the methane in the lake to reduce the possibility of a limnic event. In 2010, KivuWatt, the first methane-extraction platform, was proposed and it went online in 2015 at 26.2 MW of output, which was later increased to 34 MW. Recently, two more platforms have been approved for development, one at 56 MW and the second at 25 MW. When these are in service, this will total 125 MW of power. While this might seem extremely small, Rwanda’s total electricity capacity in 2018 was only 218 MW. The two additional plants will therefore add a significant amount of additional capacity to the country. The estimated 65 cubic kilometers of methane in the lake would last for more than 50 years.
Then in February of this year Rwanda signed a $400 million agreement with a company called Gasmeth Energy to extract methane from the lake and directly bottle the methane gas for direct use by consumers.
This methane gas mining from the bottom of Lake Kivu is an interesting, unusual source of renewable electricity. It is “renewable” because it is already existing, produced by a natural process. The CO2 in the lake is still of great concern, but since Lake Kivu is 200 times the size of Lake Nyos, withdrawing the CO2 from the lake would be a major engineering problem.
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