An Amazing New Alternative to Synthetic Fertilizer

Crops need nutrients to produce a good harvest. Specifically, they need nitrogen, phosphorus and potassium. Farmers often use synthetic fertilizers to supply these nutrients, but at a high environmental cost from mining and production. And there’s an increasingly high financial cost as well, when the products are even available.

Where else can these nutrients be found? Think way outside the box and you might come up with the answer…in human urine! An adult produces between 100 and 150 gallons of urine per year, containing about nine pounds of nitrogen, three pounds of potassium and one pound of phosphorus. That’s enough fertilizer to grow 320 pounds of wheat. Just like animal manure, human waste can be sanitized and transformed into natural, sustainably produced fertilizer for agricultural use.

The Rich Earth Institute in Brattleboro, Vermont is addressing the challenges of water pollution, water scarcity and food security by managing human waste. The first step is separating urine from the rest of the wastewater stream, known as urine diversion. This eliminates about 80% of the nitrogen and phosphorus pollution in wastewater. Without this (sadly, the norm throughout the world), six million tons of nitrogen are added to coastal waters every year, significantly contributing to harmful algal blooms and harming fish and wildlife.

After collection, the urine is sanitized, stored and transported for application. This process works well for local use but isn’t viable for widespread urine recycling as storage and trucking costs would be prohibitive. The Rich Earth Institute, University of Michigan and Cornell University are researching technologies to concentrate urine into a smaller volume.

Similar projects are underway around the world. In Paris, urine-diverting toilets will be installed in 600 new apartments, with the sanitized urine being used for the city’s tree nurseries and green spaces. Scientists in South Africa are investigating new ways to harvest urine’s nutrients. Other countries are researching reverse osmosis, freeze concentration and evaporation. It’s too early to tell which technologies will work. But it’s clear to all involved that the old methods of making fertilizer need to be replaced.