[ChuckMcM]

One of the applications for graphene membranes that I am watching for are large scale desalination plants. It has been shown to work for small membranes and if you had enough surface area you could build a desalinator that was using not much more energy than the energy to pump the water around.

[jws]

It looks like maybe a factor of 3 or so energy efficiency improvement is available for desalination. Current efficient processes are around 3kWh/m³†. The thermodynamic limit is about 1kWh/m³‡. That can be improved a little if you pump more seawater, there is a tradeoff there.

Treatment of fresh water is around 1kWh/m³, so it gets into the ballpark for freshwater treatment, though I presume some of the freshwater treatment needs to be performed on the desalinated seawater.

This places seawater as an equal to river or lake water for watering humans, but still expensive for watering crops; at 1kWh/m³, there would be about $1.50 of water in a $3.50 bushel of corn.

␄

† wikipedia: https://en.wikipedia.org/wiki/Desalination#Energy_consumptio...

‡ About page 12 of this presentation: http://www.nwri-usa.org/documents/Elimelech_000.pdf

[Retric]

At ~10-15 m^3 per bushel (2000 - 3000 gallons) the lowest cost intermittent electricity is under 2c/kwh. So that's closer to 20-30 cents per 3.50$ bushel of corn for energy at minimum. Though presumably there would be many other costs on top of pure energy especially if you are not operating 24/7.

https://electrek.co/2017/11/16/cheapest-electricity-on-the-p...

[ChuckMcM]

Primarily the concern was "drinking water" for people aka the urban water requirement (which includes drinking, washing, cooking, sanitation, and urban scale irrigation)

I suppose it helps the seasteading picture as well but I haven't really thought much about that.

Mostly if you can disconnect urban water planning from agricultural water planning it allows you to do things differently. Especially when it comes to water transport projects for coastal cities.

[TeMPOraL]

Wow, that's a great presentation.

I wonder how one can stumble upon more presentations/summary reports like that on current state of other globally important issues.