Monday, April 12, 2010

Desalination options multiply - is a green Sahara in the future?

The upside in the unknown realms of the desalination equation is rapidly gaining more potential as technology jumps forward in unexpected leaps. Are we at a point now, or will we be there soon, of wondering what effect large (mega) scale desalination and irrigation would have on global warming?

Even in a lower-tech world, desalination has had a huge role. Currently, there are 13,800 desalination plants operating in the world, producing a total of about 12 billion gallons of water a day. That, according to the International Desalination Association.

Consider: About 15-20% of the Earth's non-polar land surface is considered desert. Many of these areas could be spectacularly transformed if only they had access to cheap, plentiful water.

The problem with desalination is that, up until now, it has been an extremely energy intensive and, therefore, expensive process.

Two recent announcements have provided more reason to believe that larger scale desalination is already on the horizon.

Working jointly with IBM, Saudi Arabia’s national research group, King Abdulaziz City for Science and Technology (KACST), has already begun a solar-powered project that will supply 30,000 cubic meters of clean water per day to 100,000 people in the city of Al-Khafji. The KACST project is leveraging a new technology developed with IBM to allow more intense heat to be harvested from the sunlight and also foresees other innovations, such as proprietary new membranes developed for the reverse osmosis process.

Back on the other side of the planet, a Vancouver company, Saltworks, is continuing to dazzle specialists from the Middle East to Australia with its own unique version of solar-powered desalination.

Saltworks' breakthrough process uses far less energy than conventional systems. Saltworks' Thermo-Ionic™ desalination technology harnesses renewable energy sources such as dryness in the air and heat from the sun - to provide sustainable, low cost, desalinated water with minimal environmental impact.

Besides requiring only 20% or less energy than conventional desalination, other advantages of Saltworks' process include that it does not release a concentrated saltwater brine as a by-product and in fact, it could even use the brine produced by other desalination plants.

All that remains is for Saltworks to prove that its technology can be scaled up. Their initial Vancouver test plant will produce (or is producing) 1,000 liters of clean water per day.

Given that both of these new desalination processes use considerably less energy than previous technologies, it now becomes more interesting to project the potential and consequences of very large scale desalination. Indeed, there are sure to be further technological improvements in the near future. Deserts may be transformed - but at what price or benefit? Would a green Sahara accelerate global warming - or discourage it? The Aswan Dam in Egypt has wreaked havoc with the desert environment in unexpected ways. Now is the time to consider the large picture of desalination.    


The Mound of Sound said...

Alternative energy desalination plants are plainly an improvement over the fossil-fuel powered variety but they're still a toxic timebomb. Read Maude Barlow's assessment of this technology in her book "Blue Covenant." A litre of freshwater generates a litre of toxic discharge made up of the extracted salt (it's gotta go somewhere) plus the byproducts and the chemicals used to keep the osmosis filters from plugging up.

It's expensive, unsafe and potentially devastating to marine life.

Offroad Artist said...

That is a problem for sure, especially when taken to a large scale. So that is for sure one of the advantages of the Saltworks model, which actually uses brine as a "fuel". Or, rather, as an ion exchanging medium which effectively desalinates the sea water. Having a ready supply of brine makes the Saltworks process even more attractive, as it eliminates the need to make concentrated brine by evaporation from sea water. The saltworks process by itself does not remove other impurities from the water, though.

The Mound of Sound said...

Sorry CO2 but the Saltworks pitch sounds more than a little bogus. They suggest they'll use solar power to evaporate water vapour (uncaptured freshwater in effect) from saltwater and, having then created a condensed brine, use the chemical energy of that to extract salt from brine. Think about it. You exploit alternative energy to produce brine to fuel the desalination of brine. And somehow all that potentially destructive, extracted brine goes... where exactly? Oh yeah, to fuel the desalination of more brine.

Sounds like the League of Junior Alchemists are working overtime.

The Mound of Sound said...

One other problem. Water, the base of brine, has a finite salt capacity. The more salt it holds the lower its capacity to absorb more until it reaches a maximum saturation point. Yet these guys want to begin with heavily saturated water - brine - and use it to absorb yet more salt?

Really? Ya Think? And then where does that super-saturated brine go? Maybe they'll use alternative energy to evaporate it out as crystalline salt and then truck it to distant abandoned mines? Oops there goes more of that precious water vapour.

Sorry CO2 but I'm not buying this.

Offroad Artist said...

Seems illogical to use cold water to heat a house, too, doesn't it? But that's how some geo-thermal systems work.

Creating a website to store photos for free doesn't sound very profitable... but it worked out OK for the founders of flickr.

If you want to check out Saltworks further maybe MIT's Technology Review would be of interest.

As long as Saltworks is only producing 1000 liters of water a day, enough for like three people, I'll join you taking their claims with a grain of salt. But the concept is sound on a small scale according to all reports I've seen so far.

The Mound of Sound said...

Thanks for the link. I understand how the process can work and the potential energy savings suggested by the prototype but notice there's one thing missing from the explanation - what happens to the salt stripped via ions into the two "conditioning" streams. It's this residue or waste brine that's the underlying pitfall of all desalination systems. It was also interesting to note that the MIT Tech article avoided reference to the brine as a notional fuel.

The energy issue is a problem to all desalination systems. Nuclear power is now being developed for desalination technology under development in the Middle East.