Urine recycling to extract precious nutrient

The recycling of plastic bottles, paper and food at home is common across the world. But as many of the Earth’s resources become more scarce, chemical engineers are looking at new ways to recycle - including extracting precious nutrients such as phosphates from urine before it enters the sewage system.

Phosphorus is one of the elements needed to sustain life. Found in our genes, it is needed for good health, especially bones and teeth.

Current estimates suggest that phosphorus production - which occurs naturally as phosphate rocks and is mined extensively as a crop fertiliser - could peak by 2030 and stocks exhausted in the next 50-100 years.

Urine contains high concentrations of phosphates, but becomes heavily diluted - up to a 100 times - and contaminated once it leaves the home, making the recovery of phosphates much more challenging at waste water treatment plants.

Chemical engineers at the University of Florida, US, have taken a novel approach to the problem and have looked at the feasibility of removing phosphates at source. It could mean that household recycling takes a new direction in the future with the introduction of waterless urinals and ‘no-mix toilets’ to collect urine in nearby storage tanks.

The researchers at Florida were able to extract up to 97% of phosphates from urine in five minutes or less, using a technique called ion-exchange using HAIX resin, in a laboratory setting¹. The findings create the opportunity to run full-size systems which could form the basis for recovering phosphates from homes and communities in the future.

David Brown, chief executive of the Institution of Chemical Engineers (IChemE), said: “Our attitude and whole approach to recycling will need to change as we come under increasing pressure to conserve valuable, non-renewable resources like phosphorus.

“Phosphorus is one of those elements which is vital to life, but its importance is not widely known. As well as a fertiliser, it has many industrial uses and can be found in products as diverse as processed cheese, fizzy drinks, matches, detergents and toothpaste.

“The research is another great example of chemical engineers providing alternative approaches and solutions to the creation of more sustainable approaches to issues like wastewater management and recycling.”

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¹ Phosphate removal from urine using hybrid anion exchange resin - Alicia Sendrowski, Treavor H. Boyer Department of Environmental Engineering Sciences, Engineering School of Sustainable Infrastructure & Environment, University of Florida.