Kathmandu, August 11, 2025
A new study has revealed that human waste-long treated as an unwanted by-product-could become a critical solution to the world’s fertiliser shortages while cutting agriculture’s carbon footprint.
Researchers from Cornell University have found that transforming human excreta into biochar-a carbon-rich, charcoal-like material-can recover significant amounts of essential crop nutrients. The process could supply up to 7% of the world’s phosphorus demand annually from solid waste alone. When urine is also processed, that figure could rise to 15% of phosphorus, 17% of nitrogen, and 25% of potassium used in farming worldwide.
Nutrient Recovery and Waste Reduction
The method drastically reduces the volume and weight of raw waste-by as much as 90%making storage and transportation far easier than with untreated sewage sludge. Moreover, the nutrient content of biochar can be fine-tuned to suit specific crops, helping prevent the overuse of fertilisers that can cause water pollution and other environmental damage.
A Climate-Friendly Alternative
Traditional fertiliser production is energy-intensive and releases substantial greenhouse gases, especially nitrogen fertilisers produced through the Haber-Bosch process. Biochar production not only recycles nutrients but also locks away carbon in soils, creating a dual benefit for climate and food systems.
Food Security and Independence
Lead researcher Dr. Johannes Lehmann highlights that this approach could offer countries without natural phosphate reserves a pathway to agricultural independence. By recycling nutrients locally, communities could strengthen food security and reduce reliance on volatile global supply chains-an important step toward environmental justice and resilience in the face of climate change.
A Circular Future
The study positions biochar from human waste as more than just a technical solution-it is a blueprint for a circular economy in agriculture, where waste is no longer a liability but a valuable resource. Implementing such systems on a global scale could reduce pressure on dwindling mineral reserves, improve soil health, and create new economic opportunities from what we currently flush away.
