Chelsea Wald in Nature:

Scientists say that urine diversion would have huge environmental and public-health benefits if deployed on a large scale around the world. That’s in part because urine is rich in nutrients that, instead of polluting water bodies, could go towards fertilizing crops or feed into industrial processes. According to Simha’s estimates, humans produce enough urine to replace about one-quarter of current nitrogen and phosphorus fertilizers worldwide; it also contains potassium and many micronutrients (see ‘What’s in urine’). On top of that, not flushing urine down the drain could save vast amounts of water and reduce some of the strain on ageing and overloaded sewer systems.

More here.

The Fremen got it right from the get go.