Human urine: the perfect fertiliser?

Cambridge Conservation conducted its 14th annual horizon scan last year, with the findings published in the science journal Trends

in Evolution and Ecology. The team included 31 scientists, practitioners and policymakers who worked together on the most impactful topics.

Research team leader William Sutherland of Cambridge University said the issues they identified in 2023 “continue to reflect the juxtaposition between anthropogenic impacts on biodiversity and increasing technological capacity to mitigate those impacts”.

One of these was ‘Advances in converting human urine into fertiliser’.

The team wrote: “Recent disruption of supply chains for agricultural commodities has turned attention to demand for fertilisers from local sources. Meeting this demand may exacerbate global greenhouse gas emissions from synthetic fertilisers.”

In Japan, farmers use human faeces as fertiliser as it is an age-old practice.

“Recent progress in waste management and processing may herald a step change in the role of urine as a nutrient source for crops,” said Sutherland.

“One modelled system that replaced synthetic fertilisers with nutrients from human urine substantially reduced emissions of greenhouse gases, energy consumption, volume of freshwater used, and nutrient loads from wastewater,” said the Cambridge Conservation team.

New designs, still in the research stage, may help popularise urine as fertiliser by changing its odour profile and making it easier to use. Novel approaches include drying urine into solid blocks that can be applied directly to crops.