I’m an undergraduate Geography student and we’ve talked about these lakes a few times in several courses. Below is a summary of what we’ve discussed in lessons about this topic.
Lake Kivu, just like Lake Nyos, is a lake in the African Rift where magma flows below the surface degasses. The gases themselves are not toxic, but as they release very suddenly in massive amounts, they push away all the oxygen, causing all life in the vicinity to suffocate. But this only happens if the gases released are 1) heavier than air/​oxygen and 2) have nowhere to go i.e. the lake is in a valley. This is the case for both Lake Kivu and Lake Nyos.
To reiterate, the main risk is caused by all the gases releasing at once. These events don’t happen out of the blue. The water in the lake needs to saturated by the gases (but I guess one gas works too). The amount of gas that can be dissolved in the water also depends on the depth (see Figure 8 in the report linked in the original post). Whilst it is not at critical levels yet, it won’t happen overnight.
The water in Lakes Kivu and Nyos are ‘layered’ meaning that the water in the lake is very stable and doesn’t circulate a lot, if at all. This allows for gas saturation to occur in the lower layers. This gas will not release spontaneously. A trigger is needed. For Lake Nyos, this was a landslide that pushed water from the bottom to the top, causing it to degas. Lake Kivu is surrounded by hills too, but I’m not confident a small landslide will cause the entire lake to degas. There are several volcanoes in the vicinity, which could erupt and cause landslides, which in turn cause internal waves or turbulence and therefore degassing. Finally, a large amount of gas that gets inserted from the lake bed could also cause the saturation threshold to be crossed.
But even if this saturation threshold gets crossed by some water layers, it won’t cause the entire lake to degas. Only the gas molecules above the saturation threshold will form bubbles and rise through the surface. So for the lake to degas to such an extent that all the gas gets released, all the water in the lake needs to be basically turned upside down.
The report doesn’t mention any likelihood of any of these events happening. It’s also uncertain about the amount of gas that could be released and how much gas is added to the bottom of the lake.
Finally, I’d like to address the risks you identified:
Risk 1: what if the pipes will destabilise the lake?
As explained above, the pipes need to destabilise in such a way that causes turbulence with vertical movements of up to 130m. As the pipes are hollow and inserted vertically, I think it is extremely unlikely that this will happen. (For a fun at-home experiment: try inserting a straw in a glass of water with some liquid colouring to visualise the turbulence caused.). I think that most of the turbulence it does cause will cause some parts of the upper layers to move downwards, but not necessarily the other way.
Risk 2: releasing CO2 will contribute to global warming. Methane is even worse as a greenhouse gas, but it could be collected with profit. CO2 actually may be used too for fracking and for chemical and food production.
It seems like there is currently not really a way around this. Either the CO2 or CH4 gets released through the degassing explosion, or more controlled by the vertical pipes and turned into CO2 by burning the methane. So regardless of whether the amount extracted by current power plants is higher or lower than the amount added, we’re still turning it into CO2 . If we want to expand the amount of gas that we extract, we probably need to add some sort of carbon capture and storage system to the power plants. I have absolutely no clue how viable this is given current technology and the war that’s going on there, but I think it’s rather difficult
As there’s so much uncertainty about the amounts of gas and how much more degassing capacity is needed, if any at all, I’d say it’s quite difficult to estimate how much this would cost and therefore it’s difficult to give a cost-effectiveness analysis. On the other hand, if a solution is already known and it’s relatively cheap to implement it, I don’t see any reason why we shouldn’t.
For those who’d like to know more, the report linked above goes into quite some detail and includes many equations to calculate stuff related to it that is beyond my knowledge. The technical term for these kinds of eruptions is limnic eruptions.
The report doesn’t mention any likelihood of any of these events happening
May be you discuss a different report than I read. The one I read says:
In fact there is evidence of eruptions at Kivu in about 1000 year cycles and predictions based on observed accumulation rates (10-14% per year) suggest an eruption in the next 100-200 years, see Report [1].
Thanks for thinking and writing about this!
I’m an undergraduate Geography student and we’ve talked about these lakes a few times in several courses. Below is a summary of what we’ve discussed in lessons about this topic.
Lake Kivu, just like Lake Nyos, is a lake in the African Rift where magma flows below the surface degasses. The gases themselves are not toxic, but as they release very suddenly in massive amounts, they push away all the oxygen, causing all life in the vicinity to suffocate. But this only happens if the gases released are 1) heavier than air/​oxygen and 2) have nowhere to go i.e. the lake is in a valley. This is the case for both Lake Kivu and Lake Nyos.
To reiterate, the main risk is caused by all the gases releasing at once. These events don’t happen out of the blue. The water in the lake needs to saturated by the gases (but I guess one gas works too). The amount of gas that can be dissolved in the water also depends on the depth (see Figure 8 in the report linked in the original post). Whilst it is not at critical levels yet, it won’t happen overnight.
The water in Lakes Kivu and Nyos are ‘layered’ meaning that the water in the lake is very stable and doesn’t circulate a lot, if at all. This allows for gas saturation to occur in the lower layers. This gas will not release spontaneously. A trigger is needed. For Lake Nyos, this was a landslide that pushed water from the bottom to the top, causing it to degas. Lake Kivu is surrounded by hills too, but I’m not confident a small landslide will cause the entire lake to degas. There are several volcanoes in the vicinity, which could erupt and cause landslides, which in turn cause internal waves or turbulence and therefore degassing. Finally, a large amount of gas that gets inserted from the lake bed could also cause the saturation threshold to be crossed.
But even if this saturation threshold gets crossed by some water layers, it won’t cause the entire lake to degas. Only the gas molecules above the saturation threshold will form bubbles and rise through the surface. So for the lake to degas to such an extent that all the gas gets released, all the water in the lake needs to be basically turned upside down.
The report doesn’t mention any likelihood of any of these events happening. It’s also uncertain about the amount of gas that could be released and how much gas is added to the bottom of the lake.
Finally, I’d like to address the risks you identified:
As explained above, the pipes need to destabilise in such a way that causes turbulence with vertical movements of up to 130m. As the pipes are hollow and inserted vertically, I think it is extremely unlikely that this will happen. (For a fun at-home experiment: try inserting a straw in a glass of water with some liquid colouring to visualise the turbulence caused.). I think that most of the turbulence it does cause will cause some parts of the upper layers to move downwards, but not necessarily the other way.
It seems like there is currently not really a way around this. Either the CO2 or CH4 gets released through the degassing explosion, or more controlled by the vertical pipes and turned into CO2 by burning the methane. So regardless of whether the amount extracted by current power plants is higher or lower than the amount added, we’re still turning it into CO2 . If we want to expand the amount of gas that we extract, we probably need to add some sort of carbon capture and storage system to the power plants. I have absolutely no clue how viable this is given current technology and the war that’s going on there, but I think it’s rather difficult
As there’s so much uncertainty about the amounts of gas and how much more degassing capacity is needed, if any at all, I’d say it’s quite difficult to estimate how much this would cost and therefore it’s difficult to give a cost-effectiveness analysis. On the other hand, if a solution is already known and it’s relatively cheap to implement it, I don’t see any reason why we shouldn’t.
For those who’d like to know more, the report linked above goes into quite some detail and includes many equations to calculate stuff related to it that is beyond my knowledge. The technical term for these kinds of eruptions is limnic eruptions.
Thanks for these details!
May be you discuss a different report than I read. The one I read says:
Sorry for my late reply, but thanks for mentioning. I edited my reply to remove that section.