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Likewise the title, could you?

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  • $\begingroup$ You surely could, but you'll need a truly exotic environment to necessitate and justify such a measure. Short of "The Martian", I can't think of a realistic example. $\endgroup$ Feb 20 '19 at 22:19
  • $\begingroup$ "Upstairs" (on the ISS), this is basically done daily, where diverted urine (mostly generated from drinking water, yet equally from respired air and food) is recycled into drinking water, too (en.wikipedia.org/wiki/International_Space_Station#Life_aboard). $\endgroup$
    – Buttonwood
    Feb 20 '19 at 22:19
  • $\begingroup$ Capturing water from plant respiration is quite doable. Now, whether you consider that combustion or not is a different question. $\endgroup$
    – Jon Custer
    Feb 21 '19 at 0:02
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In short: Yes, already demonstrated.

"In long": Yes, but is more complicated than it seems.

The products of the complete combustion of hydrocarbons and other organic matter in atmospheric air usually result in the textbook products of carbon dioxide, and water.

The water may be condensed, and used. The carbon dioxide is vented to the atmosphere.

However, combustion is almost never perfect, and the fuel rarely is a pure, well defined compound. Each impurity will add something to the products of the combustion. Nitrogen compounds will add nitrogen oxides, sulphur compounds will add sulphur dioxide, etc. All of this will be present in the condensed water in one form or another (for example, sulphur trioxide will react with water producing sulphuric acid), contaminating it.

Not to mention, there is also the problem of condensing and collecting the water from the exhaust stream. To condense water you have to dissipate a lot of heat from the water vapor.

From a practical point of view, it was done before. The US Army investigated and demonstrated extracting potable water from diesel engine exhaust, as seen at https://apps.dtic.mil/dtic/tr/fulltext/u2/a576788.pdf

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