Rethinking desalination

[Ace Pace]

Not such a life saver after all?

Last month saw the release of a UN report that paints a very bleak picture of how humans are shepherding natural resources on the planet. One of the greatest causes for concern is our use of fresh water, without which life is impossible.

Demands for fresh water come from both agriculture and drinking, with agriculture currently using almost 70 percent of global fresh water. The world's population is estimated to grow to nine billion within 50 years, meaning we're going to need to double the amount of fresh water for agriculture in order to feed everyone, according to the UN. Although desalination is often pointed to as the answer to this problem, a new paper published in Science suggests we are going to need to think again.

Israel is a world leader in desalination; this desert nation recently opened the world's largest desalination plant at Ashkelon, which produces 100,000,000 m3 of desalinized water each year by reverse osmosis. The massive scale of the plant also makes its product the cheapest so far, with production costs below $0.55/m3.

Unfortunately, it seems that what passes for fresh water for drinking isn't good enough to be used for agriculture. Israeli farmers have discovered that although Na+ and Cl- have been removed, so too has Mg2+, essential for plant growth. As if that weren't bad enough, boron concentrations have increased. Although boron poses no threat to human health, most crops aren't so lucky.



Last but not least, the altered ion balance in the desalinized water results in water that is less buffered, meaning that the pipes that carry it corrode faster. Although none of these problems are insurmountable, they will all result in greater costs, and in regions where millions already live below the poverty line, that's not a good thing.

[Sikon]

Adjusting magnesium is relatively trivial, given how little of it plants require, and boron concentration is not an universal problem for desalination.

[Lord Relvenous]

The world's population is estimated to grow to nine billion within 50 years, meaning we're going to need to double the amount of fresh water for agriculture in order to feed everyone, according to the UN

How does agriculture need double when the population only goes up 2.5 billion? 9 is not double 6.5, so we wouldn't need twice the food unless there's something i'm missing here.

[The Grim Squeaker]

Funnily enough, I met the man who co-wrote this study last night .
It will be interesting to see how desert/land locked nations will cope with increased transport costs and these water issues.

[Guardsman Bass]

How big of a cost increase would we be looking at to compensate for this? Obviously, it's better than no fresh water, but I'm wondering if it's high enough to restart the "pulling icebergs north from Antarctica to melt down" path to new water resources.

[Broomstick]

The world's population is estimated to grow to nine billion within 50 years, meaning we're going to need to double the amount of fresh water for agriculture in order to feed everyone, according to the UN

How does agriculture need double when the population only goes up 2.5 billion? 9 is not double 6.5, so we wouldn't need twice the food unless there's something i'm missing here.

For the most part, the best agricultural land is already in use. Those areas that remain for additional use probably include arid or even desert areas that require more water to be brought in from outside, hence the water requirement rising disproportionately. (Just a guess)

[Gil Hamilton]

The Magnesium thing shouldn't be a problem, since you can collect the metal cations and selectively isolate the magnesium. Magnesium has several insoluble compounds associated with it, so you should be able to do something like dump a strong base into your waste brine, cause the magnesium hydroxide to fall out so you can collect it and put it back in with your crop water.

[His Divine Shadow]

I am always reminded of Egypts "terraforming" of the sahara by making artificial rivers and planting trees and driving the desert back. I heard someone here say if they managed to put enough resources on this project and on a massive enough scale that it could change local weather patterns. For the wetter.

[Sea Skimmer]

I believe your thinking of Libya, which has built an extensive network of water pipelines into the desert. This is not likely to change climate; but what could do that is tunneling from the Mediterranean into the Quattra depression. This would provide hydro power, and would allow for massive evaporation of seawater into the desert, which should have pretty significant local cooling effects.

[His Divine Shadow]

Actually I was thinking of this project
http://www.encyclopedia.com/doc/1G1-19199275.html

But the Libyan thing sounds interesting, they should do that. Turn the sahara or parts of it into something greener is a good way to combat climate change I think. Besides Africa is gonna need places to grow food.

[Mayabird]

The world's population is estimated to grow to nine billion within 50 years, meaning we're going to need to double the amount of fresh water for agriculture in order to feed everyone, according to the UN

How does agriculture need double when the population only goes up 2.5 billion? 9 is not double 6.5, so we wouldn't need twice the food unless there's something i'm missing here.

For the most part, the best agricultural land is already in use. Those areas that remain for additional use probably include arid or even desert areas that require more water to be brought in from outside, hence the water requirement rising disproportionately. (Just a guess)

Also, desertification. China for instance is having a huge problem with its agricultural land drying up and blowing away. Lands that didn't previously need irrigation will probably be needing it soon.

Though I partly wonder if the thing about doubling the water requirements also includes other uses for water that aren't directly for the crops but necessary for agriculture, like manufacturing farm equipment and stuff like that.

[His Divine Shadow]

I believe China is trying to halt the advance of deserts by planting trees and planrs as a means to stop soil erosion. Fencing in the deserts so to speak.

[Sea Skimmer]

I believe China is trying to halt the advance of deserts by planting trees and planrs as a means to stop soil erosion. Fencing in the deserts so to speak.

That they are, but so far they’ve had little luck even slowing the advance of the Gobi desert towards Beijing. Some of the forests they planted have flourished, only to be literally buried by sand dunes. Israel has had more luck with these tactics, and some areas of desert have in fact been converted into scrub land, but that’s partly because Jews have been working on this for nearly 100 years, while the Chinese effort is less then half as old.

[Jaepheth]

Couldn't they pump the desalinated water inland and let it flow into a river and let the water "normalize"?