Yup, enough to sustain 1,000 x 1,000MW reactors for 100,000 years. Seawater extraction of uranium is renewable since geological processes replenish that circulating uranium as it is extracted, too. [1]
> Seawater extraction of uranium is renewable since geological processes replenish that circulating uranium as it is extracted, too.
No, it's not. Uranium once used in reactor is literally changed to other elements. And the radioactive waste is sealed in container safe for 100s of 1000s of years.
But the discussion of whether something is renewable is also a complex topic that is only true to some extent. Renewable energy sources (Wind and Solar) are technically not renewable - the production of the equipment uses raw resources that we (today) cannot renew indefinitely.
However, for both Nuclear and Solar/Wind energy we do know, that the energy sources are sufficiently abundant to sustain us almost indefinitely without us upsetting other ecological balances.
GP's claim is that seawater uranium is replenished from natural processes, not from reactor waste. That claim is true, and their link describes why. Here's another article:
There is of course a finite amount of uranium on the planet. But there's also a finite amount of fusion fuel in the sun. Neither will run out before the sun boils the oceans.
If we keep using fission long-term, it will likely be in the form of fast reactors, which get a hundred times as much energy from natural uranium because they don't just fission U235, but also U238 and transuranics. (Because of that, the waste from fast reactors only has to be securely stored for 300 years.)
If you look closely enough the sunlight that powers solar panels also comes from the fusion of hydrogen that will be literally changed to another element. But I think it's still fair to call solar renewable because the sunlight hitting the Earth is continually renewed. And while the amount of Uranium on Earth is fixed the amount of uranium in the seas is renewed from that much larger stock, so I think calling extraction of sea uranium is fair.
> No, it's not. Uranium once used in reactor is literally changed to other elements. And the radioactive waste is sealed in container safe for 100s of 1000s of years.
Sort of. What you are talking about is a technical problem and it has a solution. (and as others pointed out is not directly related to the subject at hand)
Conventional nuclear reactors require a certain level of purity in the uranium to provide stable operation. As the uranium breaks down the fuel becomes less stable. After a while they remove the fuel and then place it into storage.
However that uranium is not used up in that process. Most of it is still there. Which is one of the reasons why it's so difficult and expensive to store safely.
Theoretically you can recover that fuel in breeder reactors. Essentially recycling it. So it can be re-used in conventional reactors. The breeder reactors will still produce usable electricity as well.
And this can be done multiple times. Up to the point were most of the fissionable material is used up and it is much less radioactive and safe to handle. At that point you would combine the waste with clay and bake it into ceramic vessels that can be safely transported and stored indefinitely.
The reason why this technology hasn't moved forward is mostly to do with a couple facts. The first one being that nobody is allowed to do anything with the 'waste' as it is Federally controlled and not owned by the power company. So the operators can't do anything with it even if they wanted to.
And the second one being that during the cold war USA and other countries created vast amounts of purified uranium as part of their nuclear programs. And they have no place to put it and no use for it other than being put through nuclear reactors.
The amount of potentially unlimited power left laying on the table because of politics, paranoia, and fear is mind boggling. If recycling is implemented we currently have many multiple generations worth of fuel stockpiled.
It could put a end to the use of fossil fuels used for energy generation within our lifetime. Which is something that is not possible with wind or solar.
That’s basically abusing the word uranium as U235 is used up while U238 is largely not in current designs.
Reprocess spent fuel lets you extract the leftover U235, but it’s a small percentage of the original amount. What you want is something like the CANDU design which is far less dependent on U235. https://en.wikipedia.org/wiki/CANDU_reactor
I was thinking of something more along the lines of an integral fast reactor were the heavy elements are removed and reused in the reactor leaving the waste "purified" of those heavy elements. So the really dangerous stuff never leaves the building and is used up to produce energy.
This means instead of having waste that is dangerous for tens of thousands of years you only have to worry about it for a few hundred.
But I guess the some of the output from a IFT then could be used in something like a CANDU reactor?
So you could use the combination of the two to use up most of the fissionable material and until the waste is so depleted that it is useless and is turned into ceramics or glass and safely stored.
Something like that.
Regardless this means that nuclear reactors provide the closest we can possibly get to truly renewable energy source and provide a path forward away from fossil fuels that could meet the energy budget of the planet for the next hundred thousand years or so.
Anybody who really cares even a little bit about the environment and global warming should be clamoring loudly for this sort of tech.
Large scale nuclear power production combined with locally produce small scale (I mean distributed) solar makes a lot of sense, IMO.
U238 isn't used in current designs because there's so much U235, and the input cost of using U235 is low enough relative to the value of the electricity generated that it's not worth using the U238 - generally speaking. It however can be used in fast neutron reactors or breeder reactors. [1]
Your general point is correct, however both U238 and U235 are are consumed by commercial reactors right now.
U238 > U239 decay into neptunium-239 which then decays into Plutonium-239. Essentially there is so much U238 in the reactor and so many neutrons flying around the above just happens.
I was under the impression commercial reactors consumed like 1% of the available U238 vs the fast reactors which got closer to 70% (based on the article linked as [1]).
Yea, it depends on the fuel and design but in absolute terms the percentage of U238 fuel used is low. However the ratio of 238v235 consumed is much closer because there is so much more U238 than U235.
To simplify if 4% of the fuel is U235 vs 96% U238. While spent fuel is say 1% U235 vs 95% U238/P239 then 3/(3 + 1) = 75% of the fuel used was U235 and 1/(3 + 1) = 25% of the fuel used was U238. Actual numbers are different, but you get the idea.
There was a math error at 1TW, 4 billion tons lasting 100,000 years means 100,000 billion tons lasts 100,000 years / 4 * 100,000 = 2.5 billion years. Though I wouldn’t be sure of the rest of those calculations.
Of course that’s also ignoring the natural decay rate of uranium, and the fact the global electricity consumption is already close to 3TW and rising rapidly. Or the fact that the chemical replacement rate likely depends on the amount of Uranium left in those rocks etc etc. None of which is important in the short term but it seriously undermines their argument.
Yes, and obvious if you are predicting out 2.5 million years that’s important. Though U238 is more plentiful and has a half life of 4.468 billion years. So, if the reactor needs a fixed amount of U235 that’s an issue but if you change the designs it’s less of a problem.
Really, it’s just more complicated than I wanted to get into.
> if you are predicting out 2.5 million years that’s important
I believe the stated claim is that there is enough fuel for 100,000 years, which is about 7000x smaller than the half-life of U-235. Even then, 2.5 million years with a 700 million year half-life is absolutely negligible. It's exponential decay, not linear, so you won't even get a 1% reduction.
> U238 is more plentiful
It's not radioactive enough; you need to subject it to a neutron flux to get something fissile, e.g. P239 through exposure in a reactor (https://www.britannica.com/technology/uranium-processing/Con...), which incidentally is what breeder reactors are designed to do.
If we're talking breeder reactors, then we have several orders of magnitude more energy available to us than the above calculations.
“It is impossible for humans to extract enough uranium to lower the overall seawater concentrations of uranium over the next billion years, even if nuclear provided 100% of our energy and our species lasted a billion years.”
Solar power doesn’t need a heat engine and can therefore avoid heating the atmosphere. We would need to be using something like 20,000 times as much energy before moving off the earth becomes useful.
In general adding heat to the earth doesn’t really matter, because it’s constantly radiating to space.
The sun shines adding a ton of heat all the time, and the same amount radiates out. Running some more power plants isn’t going to compete with the amount of energy we’re getting from the sun.
The problem comes if you add an insulator (greenhouse gas) that raises the equilibrium temperature.
I went to a talk and toured a US national lab working on this. They were using the slower method that this paper mentions. What struck me most about their process was the overall simplicity. One researcher went to goodwill, bought an old sweater, impregnated a sample of the fabric, and started capturing uranium in the span of a few hours.
They walked me through a cost analysis that borrowed methods and tools from commercial oyster farms. Roughly 50ft lines of prepared binding material would be anchored to a weighted line and buoyed with small floats. Long rows would be unspooled of the back of a boat, left to soak for a few weeks, pulled back in, rinsed with a mild acid, only to be put right back out again. Their calculations showed that they would yield yellow cake at 2x the 2018 market rate. This was in non-ideal conditions, namely slow moving colder water. They expected an increased yield from warmer fast moving water.
Last I talked to them, they were working with desalination plants to see if it would be feasible to post filter their brine. Preliminary cost projections indicated that they might be able to hit competitive pricing, and that was 2018 numbers. The market rate has since doubled.
I hadn't thought of that. Very elegant. One study found that the uranium absorption was much faster in warm/hot water. The reaction was 2x faster in 40C water than in 10C water. RO desal brine is usually warm, but steam distillation desal brine would be quite hot. To reduce its negative environmental impact, the hot brine is usually diluted and cooled in retention ponds before discharge. These ponds would be perfect for this uranium extraction process.
Night is when you let capillary action carry away the concentrated brine, preparatory to next day's further desalination. Pure water from day may be banked, meantime.
The full paper is on sci-hub_se, "Ultrafast and highly selective uranium extraction from seawater by hydrogel-like spidroin-based protein fiber"
> "In the natural seawater, SSUP fiber achieved a breakthrough uranium extraction capacity of 12.33 mg/g with an ultrashort equilibration time of 3.5 days, suggesting that SSUP fiber might be a very promising adsorbent for uranium extraction from the natural seawater."
A 1000 MWe reactor (gigawatt) requires about 115 tons of uranium, and this needs to be replaced about every four years. The silk protein degrades fairly rapidly in seawater, good for about 10 cycles. Some rough calculations then indicate that if the process worked, about 1,000 tons of silk protein would be required to accumulate enough uranium to fuel one reactor for one four-year cycle... with massive logistical problems (i.e. deployment, extraction, recycling, etc.)
I doubt this would be economically or energetically feasible. In contrast, a silicon PV solar plant with enough storage to generate a steady 1000 MW 24/7 seems to be a good deal less expensive.
The numbers would look a lot better if we were to switch to fast reactors, which get a hundred times as much energy from the same amount of natural uranium.
I love nuclear in the abstract (loved the LFTR presentations and other new gen), and I agree strongly that new nuclear is dumb with current economic development curves / LCOE of solar/wind and storage.
What I REALLY like about alternative energy "destroying" nuclear is that the nuclear industry it is destroying is the old PWR / Solid Rod / regulatory / proliferation regimes.
Because what nuclear REALLY needs a clean slate. When the solar/wind/battery markets and technologies stabilize, it should then provide a target for modular reactors, LFTR, etc.
Nukes will never be more competitive than they are right now, and they aren't, now. Renewables+storage cost is still in free-fall. By the time things stabilize, even just sunk-cost operating expense for a nuke, ignoring capital, will be way too high.
There will always be a place for nukes in the outer solar system, ultimately pB11 fusion. Out there, you don't need to bother with containment. On Titan or in the upper atmosphere of Venus, Saturn, Neptune, or Uranus, a reactor is as simple as a a big fabric tube with a naked pile near the bottom and a wind turbine at the top. One moving part.
With the right protein engineering approach, you could develop similar methods for almost any element you can think of - e.g. there are many millions of tons of gold in the oceans, though at a ~1e3-1e6x lower concentration than uranium.
The uranium binding peptide they're using has a remarkable affinity (7fM!?) which is about the same as the tightest natural binder we know about (biotin:streptavidin). The challenge in adapting this approach is first finding/designing proteins that can recognize the target ions, and then actually detecting whether a binding interaction is occurring. This has to be done on a very high throughput (1e6++) scale if you have hopes of evolving/optimizing your starting molecule to have higher affinity or to be more stable. Though for certain (toxic or life-essential) targets, nature may have already done the hard work and we simply have to find them.
Towards deployment, the challenges are what they lay out in the article - producing lots and lots of functional protein on a suitable scaffold with every emphasis on stability and easy, low-energy recovery.
As someone who is pro nuclear from the standpoint of it makes sense as a transitional technology to displace carbon emitting sources while we discover and deploy carbon neutral technologies, I was stuck on one detail of nuclear - a surprisingly finite fuel supply.
At the current rate of consumption, we currently have about 100 years of obtainable uranium 235 on earth available to mine.
Alternative means of obtaining uranium are enrichment of significantly more available U238 and experimental techniques like saltwater extraction - both of which are very expensive processes and have not been deployed at the scale required for electricity production.
Due to how polarizing this subject is and the fact that I know no nuclear engineers, I haven't yet gotten a straight answer on what we will do when the fuel runs out.
> One analysis found that for uranium prices could increase by two orders of magnitudes between 2035 and 2100 and that there could be a shortage near the end of the century.[70] A 2017 study by researchers from MIT and WHOI found that "at the current consumption rate, global conventional reserves of terrestrial uranium (approximately 7.6 million tonnes) could be depleted in a little over a century".[71] Limited uranium-235 supply may inhibit substantial expansion with the current nuclear technology.[72] While various ways to reduce dependence on such resources are being explored,[73][74][75] new nuclear technologies are considered to not be available in time for climate change mitigation purposes or competition with alternatives of renewables in addition to being more expensive and require costly research and development.[72][76][77] A study found it to be uncertain whether identified resources will be developed quickly enough to provide uninterrupted fuel supply to expanded nuclear facilities[78]
There are many more significant reserves of uranium. We just don't explore them because of a lack of demand. In addition, current reactors use very little of the fuel. Waste re-processing and breeders could extend supplies almost indefinitely. However, simply mining more uranium is more economically viable at the moment.
1. 4 Bn tonnes of Uranium is roughly a cube of 580m, yes it would sink, I think the concentration has diminished over time so that it wouldn't start to fission.
2. Removing it from the ocean would reduce the concentration and so make it more difficult to remove more.
3. If only we could do something like this to remove CO2 from the ocean since its in balance with the atmosphere. Adding an alkali to the ocean could mop up some CO2.
3a. There's the whole idea of spreading the Earth with simulated Whale faeces which adds the nutrients for the plankton to thrive.
3ai. Ideally the population of whales would grow to reduce that. However the population of whales will only slowly increase and whales would then be more likely to collide with freight ships (freight ships are more efficient the larger they are, perhaps that's why whales are so large)
3aii. As the populations of whales increase I'd imagine there would be more risk of whales spreading disease (what diseases do whales get?)
One thing is that as one extracts other minerals from the salt, the concentration of what remains increases, providing that the processed material isn't polluted with other chemicals used to separate the first pass extractions.
This technology uses polyethylene fibers coated with amidoxime. A quick look at Wikipedia reveals that oximes are commonly used as ligands and sequestering agents for metal ions [1]. I wonder -- are there useful amounts of other metals captured by these fibers? Gold? Silver? Rare-earths?
50 comments
[ 2.6 ms ] story [ 115 ms ] thread[1] https://www.ans.org/news/article-1882/nuclear-power-becomes-...
No, it's not. Uranium once used in reactor is literally changed to other elements. And the radioactive waste is sealed in container safe for 100s of 1000s of years.
However, for both Nuclear and Solar/Wind energy we do know, that the energy sources are sufficiently abundant to sustain us almost indefinitely without us upsetting other ecological balances.
https://cna.ca/2016/07/27/theres-uranium-seawater-renewable/
There is of course a finite amount of uranium on the planet. But there's also a finite amount of fusion fuel in the sun. Neither will run out before the sun boils the oceans.
If we keep using fission long-term, it will likely be in the form of fast reactors, which get a hundred times as much energy from natural uranium because they don't just fission U235, but also U238 and transuranics. (Because of that, the waste from fast reactors only has to be securely stored for 300 years.)
Sort of. What you are talking about is a technical problem and it has a solution. (and as others pointed out is not directly related to the subject at hand)
Conventional nuclear reactors require a certain level of purity in the uranium to provide stable operation. As the uranium breaks down the fuel becomes less stable. After a while they remove the fuel and then place it into storage.
However that uranium is not used up in that process. Most of it is still there. Which is one of the reasons why it's so difficult and expensive to store safely.
Theoretically you can recover that fuel in breeder reactors. Essentially recycling it. So it can be re-used in conventional reactors. The breeder reactors will still produce usable electricity as well.
And this can be done multiple times. Up to the point were most of the fissionable material is used up and it is much less radioactive and safe to handle. At that point you would combine the waste with clay and bake it into ceramic vessels that can be safely transported and stored indefinitely.
The reason why this technology hasn't moved forward is mostly to do with a couple facts. The first one being that nobody is allowed to do anything with the 'waste' as it is Federally controlled and not owned by the power company. So the operators can't do anything with it even if they wanted to.
And the second one being that during the cold war USA and other countries created vast amounts of purified uranium as part of their nuclear programs. And they have no place to put it and no use for it other than being put through nuclear reactors.
The amount of potentially unlimited power left laying on the table because of politics, paranoia, and fear is mind boggling. If recycling is implemented we currently have many multiple generations worth of fuel stockpiled.
It could put a end to the use of fossil fuels used for energy generation within our lifetime. Which is something that is not possible with wind or solar.
Reprocess spent fuel lets you extract the leftover U235, but it’s a small percentage of the original amount. What you want is something like the CANDU design which is far less dependent on U235. https://en.wikipedia.org/wiki/CANDU_reactor
I was thinking of something more along the lines of an integral fast reactor were the heavy elements are removed and reused in the reactor leaving the waste "purified" of those heavy elements. So the really dangerous stuff never leaves the building and is used up to produce energy.
This means instead of having waste that is dangerous for tens of thousands of years you only have to worry about it for a few hundred.
But I guess the some of the output from a IFT then could be used in something like a CANDU reactor?
So you could use the combination of the two to use up most of the fissionable material and until the waste is so depleted that it is useless and is turned into ceramics or glass and safely stored.
Something like that.
Regardless this means that nuclear reactors provide the closest we can possibly get to truly renewable energy source and provide a path forward away from fossil fuels that could meet the energy budget of the planet for the next hundred thousand years or so.
Anybody who really cares even a little bit about the environment and global warming should be clamoring loudly for this sort of tech.
Large scale nuclear power production combined with locally produce small scale (I mean distributed) solar makes a lot of sense, IMO.
[1] https://energyeducation.ca/encyclopedia/Breeder_reactor
U238 > U239 decay into neptunium-239 which then decays into Plutonium-239. Essentially there is so much U238 in the reactor and so many neutrons flying around the above just happens.
To simplify if 4% of the fuel is U235 vs 96% U238. While spent fuel is say 1% U235 vs 95% U238/P239 then 3/(3 + 1) = 75% of the fuel used was U235 and 1/(3 + 1) = 25% of the fuel used was U238. Actual numbers are different, but you get the idea.
Of course that’s also ignoring the natural decay rate of uranium, and the fact the global electricity consumption is already close to 3TW and rising rapidly. Or the fact that the chemical replacement rate likely depends on the amount of Uranium left in those rocks etc etc. None of which is important in the short term but it seriously undermines their argument.
Really, it’s just more complicated than I wanted to get into.
I believe the stated claim is that there is enough fuel for 100,000 years, which is about 7000x smaller than the half-life of U-235. Even then, 2.5 million years with a 700 million year half-life is absolutely negligible. It's exponential decay, not linear, so you won't even get a 1% reduction.
> U238 is more plentiful
It's not radioactive enough; you need to subject it to a neutron flux to get something fissile, e.g. P239 through exposure in a reactor (https://www.britannica.com/technology/uranium-processing/Con...), which incidentally is what breeder reactors are designed to do.
If we're talking breeder reactors, then we have several orders of magnitude more energy available to us than the above calculations.
that was a typo it should have been billion.
“It is impossible for humans to extract enough uranium to lower the overall seawater concentrations of uranium over the next billion years, even if nuclear provided 100% of our energy and our species lasted a billion years.”
At which point decay rates do matter.
I hadn’t thought of that angle until I read Gerald K. O’Neil’s book 2081
https://en.wikipedia.org/wiki/2081:_A_Hopeful_View_of_the_Hu...
The upshot being at a certain point it would be wise move heavy industry into space.
Of course rocket fuel production, rocket launches, and material orbital de-acceleration down to Earth would be issues.
My point being that Nuclear power will at some point have its own issues.
Edit: GOK’s book in question being 2081, not 2086 (confused with Japanese Anime ‘Thunderbirds 2086’
https://en.wikipedia.org/wiki/Thunderbirds_2086)
The problem comes if you add an insulator (greenhouse gas) that raises the equilibrium temperature.
https://en.wikipedia.org/wiki/Peter_Watts_(author)
They walked me through a cost analysis that borrowed methods and tools from commercial oyster farms. Roughly 50ft lines of prepared binding material would be anchored to a weighted line and buoyed with small floats. Long rows would be unspooled of the back of a boat, left to soak for a few weeks, pulled back in, rinsed with a mild acid, only to be put right back out again. Their calculations showed that they would yield yellow cake at 2x the 2018 market rate. This was in non-ideal conditions, namely slow moving colder water. They expected an increased yield from warmer fast moving water.
Last I talked to them, they were working with desalination plants to see if it would be feasible to post filter their brine. Preliminary cost projections indicated that they might be able to hit competitive pricing, and that was 2018 numbers. The market rate has since doubled.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5706215/figure/...
> "In the natural seawater, SSUP fiber achieved a breakthrough uranium extraction capacity of 12.33 mg/g with an ultrashort equilibration time of 3.5 days, suggesting that SSUP fiber might be a very promising adsorbent for uranium extraction from the natural seawater."
A 1000 MWe reactor (gigawatt) requires about 115 tons of uranium, and this needs to be replaced about every four years. The silk protein degrades fairly rapidly in seawater, good for about 10 cycles. Some rough calculations then indicate that if the process worked, about 1,000 tons of silk protein would be required to accumulate enough uranium to fuel one reactor for one four-year cycle... with massive logistical problems (i.e. deployment, extraction, recycling, etc.)
I doubt this would be economically or energetically feasible. In contrast, a silicon PV solar plant with enough storage to generate a steady 1000 MW 24/7 seems to be a good deal less expensive.
https://www.nuclear-power.com/nuclear-power-plant/nuclear-fu...
https://www.osti.gov/servlets/purl/231377
Just kidding, I know you are talking about him. But as you can see, he kind of changed his mind over time.
What I REALLY like about alternative energy "destroying" nuclear is that the nuclear industry it is destroying is the old PWR / Solid Rod / regulatory / proliferation regimes.
Because what nuclear REALLY needs a clean slate. When the solar/wind/battery markets and technologies stabilize, it should then provide a target for modular reactors, LFTR, etc.
There will always be a place for nukes in the outer solar system, ultimately pB11 fusion. Out there, you don't need to bother with containment. On Titan or in the upper atmosphere of Venus, Saturn, Neptune, or Uranus, a reactor is as simple as a a big fabric tube with a naked pile near the bottom and a wind turbine at the top. One moving part.
Seems like there is a step missing…
The uranium binding peptide they're using has a remarkable affinity (7fM!?) which is about the same as the tightest natural binder we know about (biotin:streptavidin). The challenge in adapting this approach is first finding/designing proteins that can recognize the target ions, and then actually detecting whether a binding interaction is occurring. This has to be done on a very high throughput (1e6++) scale if you have hopes of evolving/optimizing your starting molecule to have higher affinity or to be more stable. Though for certain (toxic or life-essential) targets, nature may have already done the hard work and we simply have to find them.
Towards deployment, the challenges are what they lay out in the article - producing lots and lots of functional protein on a suitable scaffold with every emphasis on stability and easy, low-energy recovery.
At the current rate of consumption, we currently have about 100 years of obtainable uranium 235 on earth available to mine.
Alternative means of obtaining uranium are enrichment of significantly more available U238 and experimental techniques like saltwater extraction - both of which are very expensive processes and have not been deployed at the scale required for electricity production.
Due to how polarizing this subject is and the fact that I know no nuclear engineers, I haven't yet gotten a straight answer on what we will do when the fuel runs out.
https://en.wikipedia.org/wiki/Nuclear_power#Uranium_resource...
> One analysis found that for uranium prices could increase by two orders of magnitudes between 2035 and 2100 and that there could be a shortage near the end of the century.[70] A 2017 study by researchers from MIT and WHOI found that "at the current consumption rate, global conventional reserves of terrestrial uranium (approximately 7.6 million tonnes) could be depleted in a little over a century".[71] Limited uranium-235 supply may inhibit substantial expansion with the current nuclear technology.[72] While various ways to reduce dependence on such resources are being explored,[73][74][75] new nuclear technologies are considered to not be available in time for climate change mitigation purposes or competition with alternatives of renewables in addition to being more expensive and require costly research and development.[72][76][77] A study found it to be uncertain whether identified resources will be developed quickly enough to provide uninterrupted fuel supply to expanded nuclear facilities[78]
1. 4 Bn tonnes of Uranium is roughly a cube of 580m, yes it would sink, I think the concentration has diminished over time so that it wouldn't start to fission.
2. Removing it from the ocean would reduce the concentration and so make it more difficult to remove more.
3. If only we could do something like this to remove CO2 from the ocean since its in balance with the atmosphere. Adding an alkali to the ocean could mop up some CO2.
3a. There's the whole idea of spreading the Earth with simulated Whale faeces which adds the nutrients for the plankton to thrive.
3ai. Ideally the population of whales would grow to reduce that. However the population of whales will only slowly increase and whales would then be more likely to collide with freight ships (freight ships are more efficient the larger they are, perhaps that's why whales are so large)
3aii. As the populations of whales increase I'd imagine there would be more risk of whales spreading disease (what diseases do whales get?)
https://pubs.rsc.org/en/content/articlehtml/2017/ew/c6ew0026...
One thing is that as one extracts other minerals from the salt, the concentration of what remains increases, providing that the processed material isn't polluted with other chemicals used to separate the first pass extractions.
This technology uses polyethylene fibers coated with amidoxime. A quick look at Wikipedia reveals that oximes are commonly used as ligands and sequestering agents for metal ions [1]. I wonder -- are there useful amounts of other metals captured by these fibers? Gold? Silver? Rare-earths?
[1] https://en.wikipedia.org/wiki/Oxime It talks about the amidoxime-coated fibers.