Greening Deserts to Sequester Carbon

[Techno-Druid]

I stumbled on to this interesting map on DeviantArt. The Sahara used to have large bodies of water: inland seas and megalakes while the Arabia early humans out of Africa migrated through was likely green.

The question is, is there a way to 'green' parts of North Africa and the Middle East through cheap and efficient geoengineering?

If canals were built to depressions below sea level, it could potentially poison groundwater and assuming you create inland seas you need to maintain the canals to keep the water from evaporating. But is there a way around this?

I'm not very knowledgeable in geoengineering, but this personally interests me and I'm personally interested in hearing how feasible it is?

[Zelk]

We should keep them as they are

[LMuhlen]

Should be possible, although very expensive. More than water, you need soil to develop a forest. If the Sahara was the same as what happened in South America, with the Amazon Forest receding due to colonizers turning it into cultivable area, and then this area turning to a desert, it was due to the soil being originally poor and only the Rain forest itself kept the soil usable by recycling nutrients.

There are efforts to contain the growth of the desert in Africa by reforesting its edges. Maybe one day it will recede.

[P for Pancetta]

Some people have said placing solar panels there could help driving the desert back, it would generate immense amounts of energy, and at the same time the shade provided by the panels and the panels themselves would prevent moisture from evaporating and allow plants to grow there.

[Masark]

They're currently working on a gigantic shelterbelt to keep the Sahara from expanding to start with. Once that's done and working, perhaps we can think starting about driving it back.

[Techno-Druid]

Some people have said placing solar panels there could help driving the desert back, it would generate immense amounts of energy, and at the same time the shade provided by the panels and the panels themselves would prevent moisture from evaporating and allow plants to grow there.

Wouldn't the solar panels block out sunlight for any plants though?

[LMuhlen]

Wouldn't the solar panels block out sunlight for any plants though?

Plants would still get plenty of light, mostly indirect, but potentially direct during a few hours of the day. Lots of species go by with only indirect light.

But the desert, in its core, kind of feeds itself, keeping itself a desert. Imagine what would happen to your little green experiment when sandstorms hit the place. Also, the low humidity causes extreme temperature variations. Which plant would grow with 40+ °C variations from day to night every day?

Trying to recede it from the borders sounds more viable to me. Not that I have any particular knowledge of this.

[PC2]

If the desert is uphill to precipitation then it's not worth it. Moving around water can cost a lot of money and it should be prioritized toward the agriculture industry.

[Kaleredar]

Wouldn't the solar panels block out sunlight for any plants though?

I think most plants would get enough ambient light from the intensity of the surrounding desert to receive more than enough sunlight to grow.

But the desert, in its core, kind of feeds itself, keeping itself a desert. Imagine what would happen to your little green experiment when sandstorms hit the place. Also, the low humidity causes extreme temperature variations. Which plant would grow with 40+ °C variations from day to night every day?

The solar panels would create little "micro climates" with much more stable temperatures as they retain moisture.

Now I don't know how practical that'd be towards, say, reforesting the sahara, but it's an idea.

[Deleted]

The problem is that the rivers that used to run through that part are gone now.



In the picture above you can see that the rivers there have mostly gone, without the fresh water there isn't a chance for anything to grow or to sustain a micro climate. Solar panels have been opted as a way to block sunlight to cradle plants, its a thought, but i would do it differently.

The two things that the Sahara has plenty of is space and sun, and it is connected to the ocean for a large part. We do have access to water there, its just that the water is salt and it has got to be brought/pumped to where it is needed. What i would suggest is constructing a major pipeline to pump sea water into the Sahara. Along this pipeline there would be solar farms that use a parabolic mirror to heat a small pipeline filled with olive oil or coconut oil or something to be heated by the mirrors. like this



The heat from the oil that is fed through the pipeline can be used to boil the seawater, you can then run the steam through some steam turbine to make power. Then all that is left is to run the exhaust from the steam turbine through a tunnel with a lot of surface area to let it condense back into fresh water that can be stored or used directly.

Pro's of this are that its is not very expensive to built (well yes, its not something i could afford to do but it is doable), it is durable because it would not have to be replaced any time soon like conventional solar panels would and not much upkeep. It would have a very little waste, everything can be used, the fresh water, the power and even the sludge that remains after boiling the water is useful. If nothing else the salt can be used on roads in the north to avoid frozen roads (the salt that is used now is mined). Even if the power production part fails you can still boil the water and have the fresh water. And if you really want to go all out there could be some sort of storage system for oil so it could run at night as well as during the day.

[Deleted]

Deserts are very light (in color), though, and as such they reflect a lot of light, and as such heat, back into space. Forests, on the other hand, are much darker, and would bind that energy on the planet, and as such they would cause a rise in temperature. Same goes for dark lakes and rivers.

There have actually been ideas such as painting roofs and even roads white to create more light colored, reflecting surface areas. I'm not sure it would be the best of ideas to darken the existing ones.

[Deleted]

Deserts are very light (in color), though, and as such they reflect a lot of light, and as such heat, back into space. Forests, on the other hand, are much darker, and would bind that energy on the planet, and as such they would cause a rise in temperature. Same goes for dark lakes and rivers.

There have actually been ideas such as painting roofs and even roads white to create more light colored, reflecting surface areas. I'm not sure it would be the best of ideas to darken the existing ones.

The forest would absorb the energy and convert it into plants, they do not keep the energy like a dark lake would.

[Deleted]

The forest would absorb the energy and convert it into plants, they do not keep the energy like a dark lake would.

Would a forest absorb all of the energy though, and not heat up the area at all? I feel like thick forests tend to be warmer than open areas, so there'd probably be some heat being trapped because of them.

They'd eat up CO2, for sure, so there's that. However, perhaps it might be a better idea to re-forest dark farmlands instead, rather than deserts.

[Afrospinach]

The heat from the oil that is fed through the pipeline can be used to boil the seawater

You will never boil seawater to make fresh, you will used reverse osmosis or another such technology. Boiling it off is extremely energy intense.

Incidentally this kind of project would probably be easier in Australia. It is all one country.

[Deleted]

Would a forest absorb all of the energy though, and not heat up the area at all? I feel like thick forests tend to be warmer than open areas, so there'd probably be some heat being trapped because of them.

They'd eat up CO2, for sure, so there's that. However, perhaps it might be a better idea to re-forest dark farmlands instead, rather than deserts.

The plants to retain some of the heat, but at the same time the heat in deserts that isn't absorbed by plant life will be dissipated in the miles of atmosphere surrounding it. There only is a negative heat signature if there are plants, at least, that is what i understood from it.

- - - Updated - - -

You will never boil seawater to make fresh, you will used reverse osmosis or another such technology. Boiling it off is extremely energy intense.

Incidentally this kind of project would probably be easier in Australia. It is all one country.

But what you seem to forget is that the energy to boil the water is already there and you need to boil water in order for the energy you have to be converted into electricity, so the fresh water is a mere byproduct of producing electricity if you use sea water instead of fresh water.

[Yunru]

The only way they can fix it if they change desert into a glass (not radioactive of cose) as glass can hold water. Then adding some shade from heat (like solar pannels) and earth from other places should fix it. Of couse they would have to pump sea water from north, remove salt and use this water in oasis.

There is a way to use salt water as power source:
https://auto.howstuffworks.com/fuel-...water-fuel.htm

[Afrospinach]

But what you seem to forget is that the energy to boil the water is already there and you need to boil water in order for the energy you have to be converted into electricity, so the fresh water is a mere byproduct of producing electricity if you use sea water instead of fresh water.

If you are trying to make a river flow "backward" I am not sure you will ever have enough byproduct from electrical generation. If the goal here is to regreen a desert, a huge task, you are probably going to want to be focused on the most effective method of acquiring fresh water available. Since pumping aquifers is pretty counter to the point of environmental conservation your source is definitely seawater, I am pretty certain currently the best method of doing this is reverse osmosis.

If may be best to do this somewhere like western Sahara where there is essentially nothing. You can then take your enriched waste seawater, I think it is about 1/8 less fresh water than normal sea water and just dry out the sea water in the sun. This is commercially viable, they still do it in Aussie and Isreal. It is where a lot of magnesium comes from. The reason being on this scale, the increased salinity of the waste water could become a concern so you may not want to pump it back even if it is in to the Atlantic. It could probably still cause a concerning change in salinity locally. It is already something they discuss a lot in Dubai and the surrounding states because they have a compounding issue of their gulf not having free flowing passages to the greater ocean. The salinity there is increasing.

Would a forest absorb all of the energy though, and not heat up the area at all? I feel like thick forests tend to be warmer than open areas, so there'd probably be some heat being trapped because of them.

They'd eat up CO2, for sure, so there's that. However, perhaps it might be a better idea to re-forest dark farmlands instead, rather than deserts.

The most effective plant is absorbing around 5% of sunlight(sugar cane or casava, trees much worse). Forests(AFAIK) *do* absorb more sunlight because of their albedo vs a desert in spite of their photosynthesizing ways. In the long run though, there could be a profound change in climate, a reduction in your systems needs to constantly add more water, cloud cover where there was never really any clouds, a reduction in dust(cannot be stated how much dust there is at certain times in west Africa, you can stay outside all day in the sun and you will get a pleasant tan with no sunblock, not burn). If you were really prolific the effects could be global and possibly not good for everyone.

https://en.wikipedia.org/wiki/Albedo

Talks a bit about what trees and various other types of terrains interaction to to the environment. Not a simple answer.

[Deleted]

If you are trying to make a river flow "backward" I am not sure you will ever have enough byproduct from electrical generation. If the goal here is to regreen a desert, a huge task, you are probably going to want to be focused on the most effective method of acquiring fresh water available. Since pumping aquifers is pretty counter to the point of environmental conservation your source is definitely seawater, I am pretty certain currently the best method of doing this is reverse osmosis.

If may be best to do this somewhere like western Sahara where there is essentially nothing. You can then take your enriched waste seawater, I think it is about 1/8 less fresh water than normal sea water and just dry out the sea water in the sun. This is commercially viable, they still do it in Aussie and Isreal. It is where a lot of magnesium comes from. The reason being on this scale, the increased salinity of the waste water could become a concern so you may not want to pump it back even if it is in to the Atlantic. It could probably still cause a concerning change in salinity locally. It is already something they discuss a lot in Dubai and the surrounding states because they have a compounding issue of their gulf not having free flowing passages to the greater ocean. The salinity there is increasing.



The most effective plant is absorbing around 5% of sunlight(sugar cane or casava, trees much worse). Forests(AFAIK) *do* absorb more sunlight because of their albedo vs a desert in spite of their photosynthesizing ways. In the long run though, there could be a profound change in climate, a reduction in your systems needs to constantly add more water, cloud cover where there was never really any clouds, a reduction in dust(cannot be stated how much dust there is at certain times in west Africa, you can stay outside all day in the sun and you will get a pleasant tan with no sunblock, not burn). If you were really prolific the effects could be global and possibly not good for everyone.

https://en.wikipedia.org/wiki/Albedo

Talks a bit about what trees and various other types of terrains interaction to to the environment. Not a simple answer.

The point i was trying to make is that for reverse osmosis you need electricity and technology, so you are either going to have to put a massive solar panel park there or you can collect the heat and produce power via steam turbine and create electricity that way.
Even though reverse osmosis is the most efficient tool in desalinizing water, you do need electricity in order to make it work. The way i proposed you will get electricity and water in a relatively simple way that doesn't have half of the cost and technical requirements that a solar panel park combined with reverse osmosis has.

This cant be done without using salt water, so you are going to have to deal with the salt anyway. It could be shipped to northern countries to be used for make roads ice free.

You can always use the power generated by the steam turbine to desalinize more sea water, so even though a solar panel park might have more out put and reverse osmosis might be more power efficient they will have to be if they want to make as much fresh water as opting to do it via steam and heat. As the steam and heat produce fresh water, and then you can always produce more fresh water via reversed osmosis with the power you produced with the steam. And all this is more durable then a solar panel park as it doesn't have a 0.5% to 1% decline of function every year (as solar panels do).

So imo it would be cheaper to do it this way, use less rare materials and it can be made "locally" as it is much more easy to make a parabolic mirror then it is to make a good solar panel.

[Techno-Druid]

I imagine the Middle East would be far easier than North Africa. I believe Israel has a lot of afforestation and waterhole projects that have been successful in the Negev Desert. It seems like much of the Levant could be forested or at least turned into savanna.

Would also be beneficial to humans and animals, I imagine.

[Low Hanging Fruit]

Anything is doable if we put our mind and resource to it. The problem is trying to figure out how to explain to rich people that they get anything out of it. When you got 15 houses with 24 karat gold shower curtains, diamonds in your Bentley interior, and have politicians eating out of your hand it is a hard sell to shift resources from things that make you happy and make you more money to things that really don't do anything for you, things you wont see in your life time really happen, and things that might help others/humanity/science/whatever more than it helps them right now immediately.