ISRN SLU-LT-R-251-SE Life Cycle Assessment of Grain Production Using Source-Separated Human Urine and Mineral Fertiliser

Source-separation of human urine is one promising technique for closing the nutrient cycle, reducing nutrient discharge and increasing energy efficiency. Separated urine can be used as a valuable fertiliser in agriculture, replacing mineral fertiliser. However, a proper handling of the urine at farm level is crucial for the environmental performance of the whole system. This study started from an agricultural point of view, demonstrating how grain production systems using human urine might be designed. The main objective was to evaluate the consequences on environmental impact and resource management when human urine replaced mineral fertiliser in arable farming. Production of winter wheat and spring barley when only mineral fertilisers were used was compared to a scenario where a combination of human urine and mineral fertilisers was used. The method for assessing the two different scenarios was Life Cycle Assessment (LCA), and the functional unit was 1 kg of grain. In the systems analysis, a change-orientated perspective was used whereby all major changes in the agricultural system using urine (the urine-separating scenario) were taken into account, compared to the conventional scenario. When urine is separated from the remainin