First off, you may be thinking why would anyone collect human urine to use on edible crops. Well we are literally pissing away free fertilizer an causing major pollution as we flush it away.
An incredible 330 tonnes of nitrogen and 20 tonnes of phosphorus a day could be retrieved from urine if 10% of the US population collect their urine.
If the thought of using human urine as a plant fertilizer grosses you out or even scares well let's just look at the facts. The visceral response to be disgusted is probably quite a normal one, but the facts and results teaches otherwise.
What about pharmaceuticals in urine and other bacteria?
Well researchers have found that human pee can be used without fear that it will lead to antibiotic resistance as long as it has been stored before use. Source
It gets a bit more complicated with removing drugs from the urine but it is feasible even up to 90%.
Adsorption of pharmaceuticals with varying degrees of aromaticity and functional groups suggests that other pharmaceuticals with comparable structures will also be removed from solution by biochar. The similar performance by biochar in different waste water compositions shows the flexibility of biochar to be applied in different treatment settings, e.g., immediately for treatment of fresh urine, after storage for treatment of hydrolyzed urine, or after transport to a central location for treatment of wastewater effluent. The removal of both nutrients and pharmaceuticals suggests that biochar can act as an alternative sorbent to result in a micropollutant-free nutrient product for agriculture. Source
If you are using your urine from a source i.e. a person that is free from pharmaceuticals then really there shouldn't be any concern. Especially if this human liquid gold plant food is being used on just your garden.
This example from China will make you laugh and marvel at the commonsense resourcefulness of using urine to increase crop yields. ARTE aired the Urine Superpowers in Germany and France on 14 November 2014
You could dilute fresh urine with water or use straight depending on the plants or the best part is you can always increase the nutrient recover and reduce the smell. Of course you could do it like this too.
However, by using some of the juice from making sauerkraut you can ferment the fresh urine which is quite a remarkable innovation. I'm sure people will be wondering how they came up with that idea, but let's just be glad they did.
During storage of urine, urea is biologically decomposed to ammonia, which can be lost through volatilization and in turn causes significant unpleasant smell. In response, lactic acid fermentation of urine is a cost-effective technique to decrease nitrogen volatilization and reduce odour emissions. Source
With so many people looking to go zero waste this is a very natural next step. It also fits great with people using composting toilets, whether in van life, tiny houses or while living off-grid.
Talk about closing the loop. Grow cabbage using urine as fertilizer and make sauerkraut to then treat the urine!
Results showed that the urine-treated cabbages grew to be bigger than the other groups. Those plants also carried fewer germs.
So, how does a pee-grown cabbage taste? Just fine, the researchers say.
They made sauerkraut from cabbages grown in all three conditions. A panel of tasters noticed differences in flavors among the groups, but they liked all three equally.
Nutrients in a person’s urine depend on what she or he has eaten. Analyses of urine used in the new experiments, however, show it contained amounts of nitrogen, phosphorus, and potassium that were similar to concentrations of those nutrients found in commercial fertilizer.
According to the team’s calculations, urine collected from one person throughout a year could fertilize a 90-square meter (970-square foot) plot of soil. More than 160 cabbages could grow in that space. Source
It is so great to see the research is there too which puts this under a logical lens. Not only for urine, but also for the backend waste ie poop.
This study showed that lacto-fermented faeces and bio-waste, supplemented by urine charged biochar can serve as a potential suitable soil conditioner. Besides, it showed that lacto-fermented urine can be a potential bio-fertilizer for improving soil quality and crop yield. The results of this thesis can be useful for improving the resource oriented potential of urine diverting dry toilets. Source
Be sure to checkout peeponics or anthroponics and the work of anthroponixGreat to see this institute doing incredible work too in the USA.