Here's an analysis we did on how many pounds of wheat (and loaves of bread) could be grown using only the fertilizer contained in one person's yearly urine output. This figure didn't make it into the National Geographic article, but it's really important for understanding the potential for urine recycling to replace synthetic fertilizers at a large scale. Of course urine-derived fertilizer could be applied to any other food or non-food crops, but we thought the huge pile of bread was the more accessible measure.

And if you look closely at the numbers, you'll see one of the most surprising things of all: that nearly 90% of the nitrogen (and 2/3 or better of the potassium and phosphorus) in human waste is in the urine!

Abe Noe-Hays, Research Director, Rich Earth Institute

Abe Noe-Hays here--Research Director at the Rich Earth Institute. One thing I should add is that starting this spring we are participating in a two-year study (headed by the University of Michigan) measuring the levels of pharmaceuticals in urine collected from public toilets, and tracking the movement of those pharmaceuticals into soil, groundwater, and plant tissues. The soil ecosystem is very good at breaking down complex compounds, but some drugs are considerably more resistant to decomposition than others and we are interested to see how they behave. If you want to follow our progress, please sign up for our newsletter! Thanks, mellon, for quoting our FAQ into the conversation.