Human Waste: A 13% Fertilizer Solution?

Human and livestock excreta contain substantial amounts of nitrogen, phosphorus, and potassium, potentially meeting 13% of global crop and grassland nutrient needs. A Cornell University study analyzed this nutrient recycling potential, finding that it could significantly reduce global net imports of mineral fertilizers. Specifically, the model indicated a possible reduction of 41% for nitrogen, 3% for phosphorus, and 36% for potassium imports.

The research emphasizes subnational nutrient flows, recognizing that local transport costs make long-distance movement of excreta impractical. Recycling poorly utilized excreta could reduce nutrient gaps by up to 20% for nitrogen in areas with insufficient local supply. This approach supports a circular economy, transforming waste into valuable agricultural resources.

Furthermore, recycling excreta can divert nutrient runoff from water sources, mitigating pollution and the occurrence of harmful algal blooms. This practice also lessens dependence on mineral fertilizer production, which has geopolitical implications and environmental costs, such as greenhouse gas emissions from nitrogen fertilizer manufacturing and the nonrenewable nature of phosphorus.