4 ms·

The brine waste from RO is still mostly water. In order to extract the salt you'd need to evaporate the water which still takes a lot more energy. You could use

The brine waste from RO is still mostly water. In order to extract the salt you'd need to evaporate the water which still takes a lot more energy. You could use evaporative ponds to let the Sun do the work but that takes a lot of space. In either case you're spending a lot more money per pound than just digging the salt out of a mine.

eropple 3y ago
Is that true when we take into account environmental externalities? I am not an expert in this field; I know that many forms of mining are capital-B Bad for the environment but I don't know how salt mines impact the area around them.
- pas 3y ago
  well, mines are bad on the short term. the long term damage is not of the actual digging, but of the separation processes. which all can be done as clean as we wish it just costs more.
  - actionfromafar 3y ago
    Cost more energy
    - Retric 3y ago
      Mining salt costs vastly less energy than using slightly brackish water. Which is why it’s so much cheaper.
- deleted 3y ago
  [deleted]
rs999gti 3y ago
> https://www.bbc.com/news/business-61483491 https://www.bbc.com/news/business-61483491 Nuclear desalination like on naval ships is the answer. US and Russian ships already have the technology, it just needs to be scaled for use on land.
- eru 3y ago
  Nuclear power in general would be the answer to a lot of energy problems. But the general public in most places doesn't like it.
  - pvaldes 3y ago
    Is not just a question of preferences, there are risks also. If the problem is that we need lots of energy to create pressure to separate salt from brine, well... I figure out that there is a lot of free "all that you can eat" pressure in the sea bottom. The problem would be to calculate if moving all this weight up and down the sea (and in open sea) would be economical or not. Or of would unavoidably lead to people cutting corners and release part of the salt to the deep water ecosystems. Deep water masses are salty yet so a small amount of salt would impact less here than if released on surface, thats for sure. In any case, physic laws about density and mass are our friend. Things either float or sink without extra energy added.
    - pvaldes 3y ago
      Having all of this in mind, I would go further and propose to regulate by law changing the material of the deep sea submarine ballasts. It seems technically doable and would have some benefits 1) Lesser impact on deep sea ecosystems. No human trace left behind. Disposable loads of iron or concrete will remain forever in the bottom. If we use salt or sand instead the impact on fragile deep sea ecosystems seems reduced. The organisms there are adapted naturally to deal with very salty water. The sand or salt ballast could be released gradually over a bigger surface reducing even more the impact over a particular spot or colony 2) Improved economics? To dump valuable iron made with valuable energy into the sea seems a suboptimal solution. Substitute it with some common by products that are yet in the area and don't need to be transported from a mine far away could save some money probably. Containers of ballast would be fully recyclable also. Ships could be adapted to literally making part the ballast on the open sea while in campaign, instead to need to carry all of it from a port. 3) Extra safety. If your load weight gets stuck by a net you are trapped in the bottom forever, With a ballast of sand or salt you have the extra possibility of open a few escape valves and let the concentrated salt go away. You can also release part of the weight much more gradually. After a while the submarine would tend to float and ascend automatically even if the energy supply would have been entirely lost in an accident. Having the machine on the surface (or closer to the surface) would save millions and would made a big difference on humanitary and economical aspects of the rescue operation. A damaged submarine can be still repaired. Building another would be much more expensive. Dunno about the possible negative aspects, more volume required for example, but would deserve thinking about it a little more.

eropple 3y ago

Is that true when we take into account environmental externalities? I am not an expert in this field; I know that many forms of mining are capital-B Bad for the environment but I don't know how salt mines impact the area around them.

pas 3y ago
well, mines are bad on the short term. the long term damage is not of the actual digging, but of the separation processes. which all can be done as clean as we wish it just costs more.
- actionfromafar 3y ago
  Cost more energy
  - Retric 3y ago
    Mining salt costs vastly less energy than using slightly brackish water. Which is why it’s so much cheaper.
deleted 3y ago
[deleted]

rs999gti 3y ago

> https://www.bbc.com/news/business-61483491 https://www.bbc.com/news/business-61483491 Nuclear desalination like on naval ships is the answer. US and Russian ships already have the technology, it just needs to be scaled for use on land.

eru 3y ago
Nuclear power in general would be the answer to a lot of energy problems. But the general public in most places doesn't like it.
- pvaldes 3y ago
  Is not just a question of preferences, there are risks also. If the problem is that we need lots of energy to create pressure to separate salt from brine, well... I figure out that there is a lot of free "all that you can eat" pressure in the sea bottom. The problem would be to calculate if moving all this weight up and down the sea (and in open sea) would be economical or not. Or of would unavoidably lead to people cutting corners and release part of the salt to the deep water ecosystems. Deep water masses are salty yet so a small amount of salt would impact less here than if released on surface, thats for sure. In any case, physic laws about density and mass are our friend. Things either float or sink without extra energy added.
  - pvaldes 3y ago
    Having all of this in mind, I would go further and propose to regulate by law changing the material of the deep sea submarine ballasts. It seems technically doable and would have some benefits 1) Lesser impact on deep sea ecosystems. No human trace left behind. Disposable loads of iron or concrete will remain forever in the bottom. If we use salt or sand instead the impact on fragile deep sea ecosystems seems reduced. The organisms there are adapted naturally to deal with very salty water. The sand or salt ballast could be released gradually over a bigger surface reducing even more the impact over a particular spot or colony 2) Improved economics? To dump valuable iron made with valuable energy into the sea seems a suboptimal solution. Substitute it with some common by products that are yet in the area and don't need to be transported from a mine far away could save some money probably. Containers of ballast would be fully recyclable also. Ships could be adapted to literally making part the ballast on the open sea while in campaign, instead to need to carry all of it from a port. 3) Extra safety. If your load weight gets stuck by a net you are trapped in the bottom forever, With a ballast of sand or salt you have the extra possibility of open a few escape valves and let the concentrated salt go away. You can also release part of the weight much more gradually. After a while the submarine would tend to float and ascend automatically even if the energy supply would have been entirely lost in an accident. Having the machine on the surface (or closer to the surface) would save millions and would made a big difference on humanitary and economical aspects of the rescue operation. A damaged submarine can be still repaired. Building another would be much more expensive. Dunno about the possible negative aspects, more volume required for example, but would deserve thinking about it a little more.