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With respect, that answer skirts the question of what happens to the water.

You said you're using the nanotube membrane to separate petro products from the water. What do you do with the water left over? What state is the water in when the process is complete? Potable? In need of treatment by traditional water treatment facilities?



I think you're asking a different question from the one being responded to (and the one being responded to is more obvious to me): I will try to help this conversation by restating the questions, both of you should correct me if I've misread this.

Your question is, in the distillation step, the nanotube membrane separates fuel from water, leaving some amount of water; what happens to that water in the process?

The question that was answered was, what happens to waste water? For which the answer is that there is no water "left over", and so the question of what happens to it is ill-defined because it doesn't exist.

So I guess what is happening is that any water left in the aqueous electrolyte can continue to be used in the process indefinitely, and there is no point at which the water becomes waste water? That all the water collected from the air gets broken up into hydrogen (in the fuel) and oxygen (waste product, sent into the atmosphere) and the amount of water in the aqueous electrolyte doesn't grow?


Correct!


Thanks for confirming, though what if the ingested air/vapor/carbon mixture has a consistently higher than required water-vapor/co2 ratio? Or is that a non-issue?


If the inputs are truly CO2 and electricity, and 100% gets converted to usable hydrocarbons, then there's no waste water; the catalyst and water remain behind.

Assuming some water is lost due to electrolysis, you can top it off over time.

If the catalyst breaks down, or some undesired reaction limits efficiency (i.e. generation of perioxide or other undesired chemicals that degrade or react with the membrane, electrodes, catalyst, etc) then I think there might be some treatment or maintenance necessary.

However, none of this sounds remotely as bad as the treatment needed in the production of petrochemicals or lithium batteries or recycling.


There is no water left either—you forgot that oxygen is also produced.


I wasn't really sure how much of the o2 generated came from the co2 and how much came from the water. Either way, I don't see "waste water" to be as big an issue as the earlier posts i was replying to did.


The water becomes the fuel. The hydrogen combines with the carbon in CO2 to form hydrocarbons, while the oxygen combines with itself to form molecular oxygen.


I would think so, but the founder says: we have a carbon nanotube membrane that replaces it, extracting the alcohols from water

This implies there is still water there. Maybe it was poor phrasing, and all of the water is consumed, but that isn't what is stated.


If water is an input and not an output, that implies it's consumed, not left over.


Yes, one of the things that gets glossed over many times in this field (I used to do research in artificial photosynthesis) is that water gets consumed to create the fuel, and is released as vapor from every engine's exhaust. So to generate 10 million barrels requires about 10 millions barrels of pure water, per day, to satiate the US.


Yes, water is turned into fuel and oxygen. In most places the water can be obtained from moisture in the air (there is much more water than CO2 in air, and we are already mining the air, so we can get both). In the process the fuel is separated from the water, which remains in the reactor, and is topped off as it is used to make the fuel. No waste water.


Somewhat tangential, but does your crystal ball show when we will start seeing carbon nanotube desalination tech making it into the real world?


His startup was supposed to start shipping it last year...


I would think so, but the founder says: we have a carbon nanotube membrane that replaces it [distillation], extracting the alcohols from water

This implies there is still water there. Maybe it was poor phrasing, and all of the water is consumed, but that isn't what is stated.


I think the water that is still there after distillation will just be used for more distillation, it just hasn't been consumed yet, it isn't a waste product.




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