Sun‑aged Human Urine Shows Promise as Low‑Cost Fertilizer and Pest Deterrent

A field trial in Niger has found that human urine left in sun‑exposed containers for several weeks to months can both supply essential plant nutrients and dramatically reduce insect damage to crops. Researchers report treated plots experienced 20.5 times less infestation than untreated controls and produced 1.8 times higher yields.

Who conducted the work: The study team includes Ibrahim Boukari Baoua (Dan Dicko Dankoulodo University of Maradi) and Laouali Amadou (National Institute of Agricultural Research, Niger), who were involved in the trial and follow‑up analysis.

How the method works: Collected urine was aged in sunlight in open containers. The sun‑warming process appears to reduce pathogen risk and produces a very strong odor — a change the researchers suspect may help deter insects. Urine is also rich in the primary macronutrients plants need: nitrogen (N), phosphorus (P) and potassium (K), which helps explain yield improvements in low‑fertility soils.

“The odor is very, very strong,” said Laouali Amadou, describing the sun‑aged containers. The team cautions that the precise mechanism for pest deterrence is not yet understood; odor, chemical transformation during aging, or other factors may contribute.

Why this could matter

In parts of West Africa where soils are poor and commercial fertilizers are expensive or scarce, a low‑cost, locally available resource like urine could reduce input costs and increase food production. Using urine also has the potential to cut reliance on synthetic pesticides and fertilizers, which can leach from fields and harm water quality and ecosystems if misused.

Important cautions

Despite promising results, experts stress important safety and environmental caveats. Other human waste products used in agriculture—such as treated sewage sludge (biosolids)—have raised concerns because they can contain persistent contaminants, notably PFAS (“forever chemicals”), and have been linked in isolated cases to livestock illness. Separate analyses have also detected various anthropogenic substances in human urine samples in some regions. For these reasons, direct reuse of urine should be paired with systematic testing, careful handling, and, where appropriate, treatment or filtration to remove contaminants.

Parallel research is exploring additional means to reduce fertilizer pollution, including materials that capture excess nitrate before it leaves fields. The research team in Niger plans further experiments to clarify why sun‑aged urine repels pests and how to optimise its fertilising benefits while minimising risks.

Practical takeaway

Sun‑aged urine could become a useful, low‑cost option for nutrient management and pest reduction in certain contexts, but it is not a ready‑made replacement for regulated agricultural inputs without additional safeguards. For home gardeners and smallholders who prefer lower‑risk alternatives, composting and other organic soil‑building practices remain effective ways to improve soil fertility without chemical inputs.