Sunday, May 06, 2007

Rwanda's Green Gas

Came across this BBC article that explores the renewable energy possibilities that could be made available to the peoples of Africa if only....

The calm, blue waters of Lake Kivu in the west of Rwanda belie the energy powerhouse it stores deep underwater. Hundreds of metres down in the inky blackness, the lake is holding enough unexploited energy to meet Rwanda's needs for 200 years. Rotting vegetation which has been deposited for millions of years at the bottom of the lake is giving off a constant regenerating supply of methane gas. Methane is a combustible gas ideal for use in electricity generation and heating, it is the main component of "natural gas" fed to cookers all over the world.

Put in simple terms, all that is needed to release the dissolved gas is to bring water up from close to the bottom of Lake Kivu, to a depth of about 70 metres. Because of the huge pressure at a depth of several hundred metres, no pumping is required to get the water up. All that needs to be done is to "agitate" the water a bit and the pressure will force it up. At 70 metres the reduction of pressure will allow the dissolved methane to bubble out of the water. Other gases like carbon dioxide and hydrogen sulphide will remain dissolved in the water, which is then pumped back down to the depths again, leaving a chamber gradually filling up with methane. The gas can then be piped away for storage and use.
Cheap, accessible and plentiful .

There are billions of cubic metres of methane at the bottom of the lake and recent studies have shown that enough is regenerated every year to supply all of Rwanda's energy needs and can also be piped to the peoples of Uganda and Democratic Republic of Congo .

It is also very prudent to begin using this trapped methane in Lake Kivu .

Geological evidence from around the lake shows that every 1,000 years or so there have been cataclysmic events which have wiped out all animal life in a huge radius surrounding the lake.
What happens is that gradually so much methane and carbon dioxide is dissolved in the water that it begins to acquire buoyancy. Instead of this being released gradually there is a sudden huge explosion, where the lake effectively turns over. The gas laden water from the bottom of the lake surges to the surface, releasing billions of cubic metres of gas; this settle like a huge toxic blanket over the surrounding area. It is heavier than air so all the oxygen is forced out and all life is suffocated. This is what happened at Lake Nyos in Cameroon in 1986, when 1,700 people were killed. Lake Kivu is hundreds of times bigger than Lake Nyos and it is estimated that more than two million people would die. Extracting methane from the lake will help to mitigate this cataclysmic eventuality.

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