Gold from Seawater

Yes, woudn't it just be nice to get all the gold out of the seas!

It is estimated that there are 20 million tons of gold in the oceans. With current prices that represents a market value of about 1,19 quadrillion US dollars, or about 47 times the current United States GDP. In layman terms, and coming from someone that know jack about Economy, that means that there is "more wealth" dissolved in the oceans of Earth than what was accumulated in the entire history of the United States' economy. 

It is not difficult to understand why there is so much gold in these waters today. Rains have been washing over mountains on continental plates since very early in Earth's geological history, The rivers carry this gold, or rather the bulk of it, into the seas. At least that is how I understand it, but I don't claim to know much about Earth geological processes, even though they do fascinate me. Oh so much to learn, so little time.

It puzzles me a little why isn't all the gold in the seawaters, already. Why we still find gold in good quantities. I can't think of a mechanism that replenishes the gold into the landmasses, so it makes a certain sense to question why hasn't all gold been washed away. I don't have an answer to that question.  

But there is a catch in getting gold out of the seas. The gold is dissolved in billions of cubic liters of waters, in a way that makes recovering it extremely difficult or perhaps even impossible. There are no universally accepted methods to recover gold from seawaters that have been proven to be economically feasible. 

For a historical perspective on the many individuals and enterprises that tried to get gold out of seawaters in the past, see this coverage, by Eric Grundhauser. A noteworthy attempt was made by famous chemist Fritz Haber in 1920s, but turned out to be unfruitful in the end. I've read somewhere that he was trying to gather funds to pay Germany's World War 1 debt with this gold.

I don't know much about the chemical state in which gold is there on the waters. It is a mystery to me. Oh Chemistry my arch-enemy. I've learned a bit here [the Science made alive portal]. My respects to whomever put this gemstone website online. The photo coverage is priceless.   

Don't worry, I'm not going to try to sell you a method to get gold out of the sea here. 

All I've done, in fact, was to assume that there was a way to filter gold out of seawater, somehow a membrane or something, that we could leave in the path of the oceanic currents filtering the seas. These nets of membranes would stay floating, filtering. Maybe they would be anchored on the bottom of the sea if that is possible. After a while, you would reel these nets filled with gold now, destroy the membranes and recover the gold. The cost of the membranes themselves are negligeable comparable to the value of the retrieved gold, what may or may not turn out to be truth. 

There is a calculation spreadsheet. It is available in the bottom of the page. It should be easy to follow what I was attempting to do there. I've used some data that is available on the Internet such as the gold concentration on Atlantic waters, seawater density, Atlantic Current speed. These stand now as first guesses, these numbers can be improved with the expertise of someone that dedicated his life to study the oceans.  

Calculation Results

The results of this spreadsheet show that it would take around 32 millenia in order to get 1kg of gold out of seawaters, if the filter area was a square of 1m x 1m. This would yield 59,391.90 US dollars, but it would take 32 millenia to get that money. 

If we change the calculation to see the area required to make 1kg of gold per hour, yielding $ 59,391.90 US dollars per hour, than it would take a filter that is a square of 16,6 km x 16,6 km. That filter has an active area of roughly 276 km2

That is one big net. The membrane would have to be particularly cheap to manufacture in order for this to have any chance of success.

And that is it, I hope you enjoyed this calculation. Leave a comment, mate!

Calculation Spreadsheet


BANNER IMAGE CREDITS: NASA, ESA and Jesús Maíz Apellániz (Instituto de Astrofísica de Andalucía, Spain) 

Want to know more about this image? Follow this external link.