Wednesday, November 07, 2007

Uranium from Seawater--Peak Uranium Most Unlikely for next 5,000 Years!

Brian Wang posted a promising look at the prospects of mining uranium oxide from seawater. How much uranium is in seawater compared to expected uranium reserves on land?
It is estimated that there is 4.7 million tonnes of uranium ore reserves (economically mineable) known to exist, while 35 million tonnes are classed as mineral resources (reasonable prospects for eventual economic extraction).[32] An additional 4.6 billion tonnes of uranium are estimated to be in sea water (Japanese scientists in the 1980s proved that extraction of uranium from sea water using ion exchangers was feasible).[33][34]

Brian estimates that the value of uranium in seawater at today's prices may approach US $720 trillion!

Uranium oxide would be retrieved from seawater with irradiated polymer (eg polyethylene) woven into netting, and moored in seawater for app. 60 days to absorb uranium. The netting would be retrieved, the uranium would be removed from the netting, the netting replaced in the sea, with the polymer absorbent re-used multiple times similar to fish nets.

Methods for improved harvesting of uranium from seawater suggested by Brian:
1. Functionalize an algae bloom to concentrate Uranium
See the work of Matt Francis at Berkeley for functionalizing virus shells and microbes for anti-cancer or for solar power. Many others are trying to engineer microbes using synthetic biology.

The goal would be to increase the concentration of Uranium from 3 parts per billion to 300 parts per million. The higher concentration allows regular methods of Uranium mining to take over. It is an increase of 100,000 times....

2. Nanomembrane Filtering
Nanomembrane filtering is starting to be used for desalinization of water at 100,000 gallons per day using a 6 inch diameter membrane.
If one could filter 1 billion gallons per day then there would be $1.92 million/day worth of Uranium. (3 mg per ton of water. 1 billion gallons is 4 million tons. 12,000 kg of Uranium in 1 billion gallons) Ten thousand of the 6 inch diameter nanomembrane enabled filtration pipes would be needed.
Advanced Nanotechnology

Here is an abstract from one of the most active Japanese research groups:
The total amount of uranium dissolved in seawater at a uniform concentration of 3 mg U/m3 in the world's oceans is 4.5 billion tons. An adsorption method using polymeric adsorbents capable of specifically recovering uranium from seawater is reported to be economically feasible. A uranium-specific nonwoven fabric was used as the adsorbent packed in an adsorption cage 16 m2 in cross-sectional area and 16 cm in height. We submerged three adsorption cages in the Pacific Ocean at a depth of 20 m at 7 km offshore of Japan. The three adsorption cages consisted of stacks of 52 000 sheets of the uranium-specific non-woven fabric with a total mass of 350 kg. The total amount of uranium recovered by the nonwoven fabric was >1 kg in terms of yellow cake during a total submersion time of 240 days in the ocean.

More here.

Seawater contains many thousands of years worth of uranium at current usage. No one actually believes that human civilisation will still be based upon nuclear fission and fossil fuels one thousand years from now. Fossil fuels will still be around then, but will be considered too dirty, expensive, and valuable to burn for fuel. Nuclear fission will still be around if needed--certainly there is plenty of uranium and thorium--and may be used in particular applications where the fuel available makes clean fission more practical.

Most tech forecasters expect nuclear fusion to be widely available for large scale power generation within the next one thousand years--if not the next one hundred years. We will not need but a fraction of the available uranium and thorium over the long run.

Of course, that prediction is based upon the continuation of western civilisation--or perhaps other successor civilisations just as friendly to scientific/technological research and personal/economic freedoms currently guaranteed by the west. A surrender to reactionary religious fanatics or ideologues (luddites) would introduce a significant element of pessimism into the forecast.

Recent pessimistic "peak oil" pronouncements have been taken far too seriously by the many uninformed persons who attempt to follow trends. A recent declaration that peak oil occurred in 2006, was particularly ludicrous--since it was based upon selective production figures without taking into account reserves or various factors that could influence their production data. Too much peak oil "research"--like much of climate change research--is infested by ideologues who assume the result and carefully craft data to fit that result.

The important thing is to understand that it is resource prices--and how society reacts to price changes--that matter in the long run. It is natural for modern societies to begin to move from more expensive (particularly if dirtier like fossil fuels) to more economical and sustainable technologies. That is basic economics and will occur over time regardless of any "Kyoto" or other treaties or regulatory schemes.

For those of us interested in the next level, the singularity, or just a very promising future, it is always important to watch important trends, while always looking a little farther ahead.
Previously published at Al Fin.

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