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According to this article:

Every megaliter of seawater contains about 1300 kg of magnesium, 900 kg of sulfur, 400 kg each of potassium and calcium, and smaller amounts of virtually every metal on the periodic table of elements.

Sodium also is present in high quantities, though perhaps it's not particularly useful for manufacturing and therefore not mentioned.

Seawater is probably one of the most sustainable sources for minerals/materials, alongside products from sustainably managed plants or animals.

Are there any websites that list products completely comprised from such sustainable sources, without mining?

I'm not asking about what could theoretically be produced, if we were able to extract tiny quantities of a mineral at great expense; I'm asking about products that are currently produced, or could easily be produced, from such sources that are already cost effective to utilise.

  • Why would mining from seawater be more sustainable than mining from subterranean land-based sources? – gerrit Mar 27 '13 at 12:41
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    @gerrit, my thought was that it would be much faster to naturally replenish, but perhaps that's not the case. I don't think this was a particularly well-worded question, but at least it might lead to a better one being asked :-) – Highly Irregular Mar 28 '13 at 7:40
  • Sea water's mineral content comes from erosion of the land and seafloor and volcanic and hydrothermal activity. These processes aren't going to stop any time soon, but neither will the natural processes that remove minerals from sea water, such as calcite precipitation by corals and shellfish. Industrial-scale mineral extraction would probably throw the ocean ecosystem for a loop, at least near the extraction facilities. – Evan Johnson Jun 7 '13 at 15:30
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Summary

  • The 4 metals currently extracted (in combination with other materials (eg "salt") or as ions in an extraction process are the only ones commercially viable at present, and may be the only ones readily able to be extracted for the forseeable future. The "big 4" are -

    • Sodium
    • Magnesium
    • Calcium
    • Potassium,
  • Energy considerations make the task of extraction non-viable in all other cases except possibly for Lithium and Uranium, due to their high energy content when used as nuclear 'fuels'. Lithium is substantially more viable in this respect but has not as yet been extracted commercially. For all other materials the need to process extremely large amounts of water mean that the energy required almost invariably greatly exceeds either that used for extraction from other sources and the "energy value" of the recovered materials.

  • Development of unconventional extraction systems using eg bacteria or sea plants or animals to concentrate materials selectively may make some other materials viable in future.


Detail:

The four most concentrated metals in sea water are Sodium, Magnesium, Calcium and Potassium, and these are the only ones commercially extractable today. The least concentrated is Potassium at 400 parts per million.

Materials below the level of concentration of the above 4 are not economically extractable by direct removal by filtering, membranes and similar due to energy considerations. The energy required to move the vast quantities of water through a filtration system typically greatly exceeds the energy needed for extraction by other means on land.

Two possible exceptions are Lithium and Uranium due to the large amount of energy released when they are used as 'fuel' in nuclear reactions.

The Japanese ran a Uranium extraction experimental system for some years but practical activity on the project seems to have ceased (see below).

Available materials can be surprisingly low. All the dissolved copper in seawater (20th in occurrence) amounts to about 50 years of use worldwide at current rates. Getting the Copper out would be a humungous task and clearly not practical.


(1) Other means: As an alternative to filtering other means have been and are being investigated which MAY have application for a range of minerals.


(2) Good discussion of energy issues

Extracting Minerals from Seawater: An Energy Analysis
Abstract here
Full free paper here {PDF}
Ugo Bardi, Dipartimento di Chimica, Università di Firenze, ... 2010

  • Abstract: ... Seawater contains large amounts of dissolved ions and the four most concentrated metal ones (Na, Mg, Ca, K) are being commercially extracted today.

    However, all the other metal ions exist at much lower concentrations. This paper reports an estimate of the feasibility of the extraction of these metal ions on the basis of the energy needed. In most cases, the result is that extraction in amounts comparable to the present production from land mines would be impossible because of the very large amount of energy needed.

    This conclusion holds also for uranium as fuel for the present generation of nuclear fission plants. Nevertheless, in a few cases, mainly lithium, extraction from seawater could provide amounts of metals sufficient for closing the cycle of metal use in the economy, provided that an increased level of recycling can be attained.


(3) Ref1: This excellent paper discusses the issues involved and provides details of attempts to extract Uranium and Lithium.

An image in Ref1 shows Japanese researchers investigating Uranium extraction!
They say -

  • The four most concentrated metal ions, Na+, Mg2+, Ca2+, and K+, are the only ones commercially extractable today, with the the least concentrated of the four being potassium (K) at 400 parts per million (ppm).

    Below potassium, we go down to lithium, which has never been extracted in commercial amounts from seawater, with a concentration of 0.17 ppm.

    Other dissolved metal ions exist at lower concentrations, sometimes several orders of magnitude lower.
    None has ever been commercially extracted.

A company set up in New Zealand a decade + ago to do Lithium extraction. It SOUNDED plausible and much money was spent. The promotrer turned out to be an internationally known con-man! :-(.

The main problem - energy cost and return.

From Ref 1:

  • Table 2. (see paper). Elements are ordered as a function of the mass of seawater that would need to be filtered in order to obtain the same amount of materials that we obtain today from traditional mining. That value is calculated in the optimistic assumption of 100% efficiency of the filtering membrane. For data sources, see note (1) at the end of the text

  • The table shows that, even for the best case listed, lithium, in order to recover the same amount we get today from conventional mining we would need to set gigantic facilities. We'd need to process at least ten times as much water as it is processed by desalination plants today. All the other metals would require to process amounts of water orders of magnitude larger.

Moving these gigantic amounts of water is not just a practical problem:
it involves energy; a critical parameter especially if we consider the extraction of two elements that are to be used as energy sources: lithium and uranium.

**In both cases, the feasibility of extraction is determined by the energy needed according to the well known concept of "EROEI" (energy returned for energy investment)


Related:

(4) The geochemistry of seawater
Table of 84 minerals in seawater here {jpg image} Copied below - order inobvious.

enter image description here

4

Seawater is no more a sustainable source of minerals than mining is. They're both depleting a finite resource, insofar as the minerals in the sea come from rock erosion anyway. There's a small difference in that some of the minerals in the sea come from waste from human activities. But in those cases, mining landfill sites or doing mineral extraction at sewage farms is going to be less resource-intensive and more cost-effective.

One big difference is that mining uses fewer resources to do the extraction, than seawater.

Another is that the ecosystem impact can be easier to mitigate with mining, though often this is not done, owing to weak regulation of miners. Seawater extraction often involves some form of filtering of very large volumes of water, close to shore, potentially with consequential high impacts on the near-shore ecosystem. Typically, vast volumes of sea water must be filtered to extract small quantities of useful minerals.

To my knowledge, the only minerals currently extracted from sea water cost-effectively are in sea salt, and they're cost-effective because they are at much higher concentrations in seawater, so solar evaporation from rock pools does most of the work.

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    It may be more sustainable than mining land based deposits if it replenishes more quickly through natural processes. Whether or not that's happening, I don't know. – Highly Irregular Mar 27 '13 at 2:46
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I haven't seen a comprehensive list. In fact all the sea mineral products I've seen on the net are for home gardening.

  • ag-usa has a list of four home gardening mineral products they say make up the market.
  • seamazing offers a similar product.

Sounds like this list will grow, along with the sea mineral products offered.

I wouldn't rush to the conclusion, however, that because these products use sea minerals, they are more sustainable. From a land use perspective, of course they will be. However, mining minerals from the sea can be very energy intensive, according to a lot of sources, mdpi for instance.

High energy intensity, depending on the energy source used, could actually lead to more air pollution, including GHGs.

  • Thanks for the answer! I consider mining and extraction from the water itself to be completely different, from a sustainability perspective. Also, you're absolutely correct (and realistic, currently) about the energy usage being a problem, but it is possible to produce renewable energy. – Highly Irregular Mar 26 '13 at 7:18

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