A new study by researchers at the Institut de Ciència i Tecnologia Ambientals (ICTA-UAB) claims that nitrogen sourced from human urine could significantly reduce the need for synthetic fertilisers, as well as reducing emissions and water usage.
The study, Urine luck: Environmental assessment of yellow water management in buildings for urban agriculture, which was published in the Resources, Conservation and Recycling journal, examines how the nitrogen recovered from so-called ‘yellow water’ could in turn be turned into nitrate, a form of nitrogen that can be absorbed by plants.
‘While only constituting around 1% of the total wastewater fraction, the majority of nutrients in wastewater come from urine,’ the researchers state. ‘Nevertheless, in developed nations, domestic wastewater is typically collected and processed in wastewater treatment plants where energy-intensive processes are required to denitrify wastewater to recover <10 % of the [nitrogen] content.
‘Implementing urine source separation through e.g. dry urinals or urine-diverting toilets is thus crucial to isolate urine from wastewater and prevent nutrient dilution. This circular approach not only facilitates the utilisation of urine for fertiliser production but also reduces the reliance on scarce natural resources for fertiliser manufacturing.’
Tomato cultivation
ICTA-UAB’s study was undertaken in a bioclimatic building at the UAB campus in Spain, where the nitrogen produced from the urine was used to irrigate hydroponic tomato crops in a rooftop greenhouse.
As the pilot study found, one cubic meter of treated urine could yield 7.5 kg of nitrogen, enough to grow and cultivate 2.4 tonnes of tomatoes. Over a year, this could rise to more than 17 tonnes of tomatoes.
Researchers also suggested that by scaling up the nitrogen recovery system, the environmental impact of the process could be halved, reducing the carbon payback time from 29 years to just 13 years. This would open up the possibilities for large-scale nitrogen recovery systems for urban agriculture.
Wastewater management
‘These findings can facilitate decision-making processes to optimise wastewater management systems, defining which one to use and promote sustainable practices in buildings,’ they stated.
‘We encourage interdisciplinary research teams to further explore potential techniques to recover [nitrogen] from urine and to demonstrate their agronomic feasibility and food safety in building integrated agriculture. This shall promote the implementation of circular strategies in buildings that facilitate the production of local food at lower environmental costs.’ Read more here.
