Australia plans to use human urine as plant fertiliser in city parks

Australia is planning to trial the use of human urine as fertiliser for plants and lawns in public city parks, as part of a four-year, government-backed project. 

The trial will see different toilet designs in parks, with urine separation technology under the U-bend that would trap the good nutrients from urine for reuse, while simultaneously removing all the unwanted chemicals like heavy metals.

Urine contains key macronutrients – potassium, phosphorus and nitrogen – needed for plant growth and is therefore an excellent fertiliser. 

Unlike mining the Earth and atmosphere for these chemicals, urine is free, abundant and totally inexhaustable. 

The trial is currently planned for public parks in Sydney and Brisbane, although authorities want to gauge the public’s response to such a scheme first.   

Dr Stefano Freguia, a chemical engineer at the University of Melbourne, has proposed one toilet design. It would use an anode and a cathode to separate chemicals in urine, using elements in the surrounding air as a catalyst

‘A TEASURE TROVE OF LIQUID GOLD’: HOW WOULD IT WORK? 

Specially-designed portaloos in public parks in Sydney and Brisbane could have urine separation technology under the U-bends.

Designs for the technology, as well as locations for the loos, are currently being considered.  

But one proposed system would use an anode and a cathode – two of the main components of batteries – to separate chemicals in urine, using elements in the surrounding air as a catalyst. 

Human urine contains about ten grams per litre and about a gram of phosphorus, making it a perfect source of nutrients to grow crops we eat.

Dr Stefano Freguia, a chemical engineer at the University of Melbourne, has already authored a paper on a potential toilet design. 

With colleagues, he’s proposed ‘the world’s first nutrient recovery system’ that powers itself and does not require human control. 

It would use an anode and a cathode – two of the main components of batteries – to separate chemicals in urine, using elements in the surrounding air as a catalyst.   

The project is being led by the Cities Research Institute (CRI) at Griffith University in Queensland, Australia, under the the $2 million ARC Research Hub for Nutrients in a Circular Economy (NICE). 

Researchers are working with state governments to identify potential trial sites before the first toilets roll out as early as later this year. 

Chief investigator, Professor Cara Beal at CRI, called human urine ‘a treasure trove of liquid gold nutrients’, which could help grow the crops that we eat. 

‘It’s a concentrated supply of all the nitrogen, phosphorus and potassium needed for plant growth and is surprisingly clean compared to other waste,’ she said.

‘We’re working with Queensland Urban Utilities, Department of Environment and Science, and Brisbane City Council Parklands Service to determine the value of urine-based fertiliser and the impact it can have on soil and plant production.’  

A given amount of human urine has potassium, phosphorus and nitrogen in similar concentrations to that found in fertiliser, Professor Beal said. 

Currently, it’s energy-intensive and expensive to extract nitrogen from the atmosphere to use in plant fertilisers, while phosphorus is a finite resource that is mined from rock. 

The US’s Center for Biological Diversity says phosphorus mining ‘violently transforms the environment and irreparably changes the character of the natural landscape. 

The trial is currently planned for public parks in Sydney and Brisbane, although authorities want to gauge the public's response to such a scheme first. Pictured is Hyde Park, Sydney (stock image)

The trial is currently planned for public parks in Sydney and Brisbane, although authorities want to gauge the public’s response to such a scheme first. Pictured is Hyde Park, Sydney (stock image)

However, direct reuse of urine is not recommended for plants due to the presence of active organic molecules and heavy metals, so filtering technology is needed. 

‘Current methods to create fertiliser pull nitrogen out of the atmosphere in an energy intensive process with a massive carbon footprint,’ said Professor Beal. 

‘As a society, if we are to get to net zero carbon emissions we are going to have to move away from synthetic fertilisers. 

‘Phosphorus on the other hand is mined, with supplies forecast to last no more than 100 years, so it makes no sense to flush these essential nutrients down the toilet.’  

Historically, humans used urine as both a fertiliser and a cleaning agent, but more recently, for the past 100 years up to 1970s, farmers used combined human waste as a fertiliser on fields.

Phosphorus, found in urine and a valuable nutrient for plants, is a finite resource that is mined from rock (stock image of phosphorus mining in California)

Phosphorus, found in urine and a valuable nutrient for plants, is a finite resource that is mined from rock (stock image of phosphorus mining in California)

‘Only recently have humans become squeamish about recycling the waste we produce to grow essential food crops and other plants,’ Professor Beal said.

‘Part of our research will investigate why we have become uncomfortable with the idea of harvesting urine for fertiliser, and how we can temper this concern.’ 

Full regulatory approval will be needed to bring these toilets to parks, as well as evidence that the scheme doesn’t pose a risk to public health in any way.  

‘The public and regulatory authorities have legitimate concerns around potential health issues the technology could pose, with the antibiotics, drugs, hormones and other chemicals we consume that end up in our waste streams,’ Professor Beal said.

FANCY A COLD GLASS OF PISNER? DANISH BREWERY RECYCLES 54,000 LITRES OF FESTIVAL GOERS’ URINE TO MAKE BEER 

A Copenhagen brewery is using urine collected at a music festival to help make its beer.

Nørrebro Bryghus has a beer called Pisner which used urine as fertiliser during the brewing process. 

The project has been branded ‘beercycling’. The brewery collected over 10,000 gallons of urine from Denmark’s Roskilde Music Festival in 2015. 

The collected urine was used to fertilise barley fields instead of other fertilisers such as animal manure. 

Karen Hækkerup, CEO of the Danish Agriculture and Food Council, said: ‘Just as we have seen shops sell goods that would otherwise have been thrown out, beercycling allows us to recycle a product that is normally flushed down the drain. 

‘When it comes to circular economy, Danish farmers are some of the best in the world. 

‘If you can brew a beer with urine as fertiliser, you can recycle almost anything.’

Brewery director Henrik Vang said: ‘We want to be a part of the beercycling project partly due to the story it has already told, but also because it is interesting to partake in a project which addresses the challenges of sustainability and circular economy.’   

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