When we think of using human waste as fertilizer—don’t you?—we tend to think of biosolids.
But solids aren’t the only human waste products that could be used in an agricultural setting. Researchers at the University of Illinois have been studying uses for urine for a while, and they have an interesting new study out that examines geography and diet as it relates to utilizing human urine on farms.
These researchers had previously studied wastewater to figure out if there was a geographic type of place that makes sense for agricultural application. They landed on an idea of large-ish cities (to produce lots of wastewater in a small space) that happen to be near lots of farmland; Chicago and Cairo would be good examples.
But there are many more variables than just population and proximity to farmland at play. The new study looks more deeply into the diet side of things. Nutrients in urine that could be useful in an agricultural setting—nitrogen, phosphorus, potassium—stay fairly constant in our bodies once we stop growing, the researchers say. So, if we eat or drink something with lots of those elements, it’ll be flushed out in our urine (like excess vitamins); the body doesn’t need to absorb any more.
The researchers took that concept and considered where the most nutrient-rich urine would be produced, along with other factors. Those factors include work similar to their previous research, on the location of population centers in relation to agricultural centers, but they also looked at sanitation facilities across 107 countries.
There’s a bit of a double-edged sword to sanitation facility data. Countries where human populations overlap substantially with agricultural areas, including India and Uganda, seem like a good bet at first—but sanitation infrastructure, say the researchers, needs improvement. That could mean facilities that take advantage of the possibility to harvest urine for its agricultural benefits could be built, but it’s also likely that financial obstacles would make that very difficult.
In countries such as the United States, where population centers are quite far away from farmland, it becomes too expensive to process and move wastewater from one place to another. But in the middle of these two extremes lie countries such as Brazil, Mexico and China. In those countries, some population centers are far from some agricultural centers, but not always; there is plenty of densely populated agricultural land, too. Those countries also have superior sanitation infrastructure (and the resources to add more), which makes them ideal for this sort of work. And having this information could allow for more efficient use of development money.