Ventilation systems are named a bit weird like that: *System A is natural convection (like holes in the walls) *system B is holes in the walls, and a motor brings fresh air in the building *System C is only a centralised extraction (needs rosters in your windows so you have an air intake, so basically an energy-label-certified-hole in your brand new windows) *System C+ is centralised extraction with a variable debit depending on CO2 and humidity detected (so it is less energy wasteful than the previous one) *System D is a double flux system: one centralised unit with a heat exchanger built in. There are 2 circuits, one is fresh air and the other one is air extraction. the house is basically always a bit over-pressurised. It is possible to obtain also humidity regulation for the winter if needed (ex build-in humidifier or enthalpy exchange units). When testing for build quality in passive houses, they check that almost all air exchange goes only through the unit *System E: System C+ with a heat exchanger connected to a centralised heat pump for the building. Never seen one outside of an expo room.
There is also the issue with the salt by itself in desalinisation. If it’s removed with water, you have to deal with that stuff. Table salt is really cheap and there is plenty of offer, so you can’t really economically clean it enough and package it for human consumption or industrial use. So what usually happens is that they dump it back at one moment or another. And that is a hard pollution, and can lead to dead zones around the desalinisation plants if not managed well enough. Being able to add it in a high demand product such as batteries takes all those hurdles away