Hold up! Fertiliser made from urine?

With the world’s soil losing nutrients at an alarming rate coupled by sharp increases in fertiliser prices, farmers are considering fresh alternatives to organic fertilisers by the day.

As it turns out, we may need to look no further than the bladders of animals (and our own!) for fertiliser to replace the nutrients that crops remove from the soil.

Before you twist your face in disapproval and wonder why this is even up for discussion, experts say urine might just be a viable alternative for farmers to explore. We know that sounds really gross, right? Has it really come down to using your own wee-wee to grow food? Unfortunately (or should we be saying “fortunately”?) so.

Agriculture is the world’s largest industry with the World Wildlife Fund estimating that pasture and cropland occupy around 50% of the Earth’s habitable land, providing habitat and food for a multitude of species. However, decades of intensive farming practices have caused soil to lose nutrients at an alarming rate.

Adding to this global problem is the fact that the materials to make widely used fertilisers are becoming increasingly difficult to obtain, say experts.

Thapelo Phiri, organic fertiliser specialist and director of Golden Legacy Trading and Projects, believe urine could be amongst the solutions to address both these issues.

Phiri’s Gauteng-based agribusiness helps farmers improve soil fertility and mitigate the effects of climate change.

He explains that because key ingredients for fertilisers, such as nitrogen, phosphorus, and potassium, are obtained from non-renewable sources, a shift towards the use of organic fertilisers will be a serious solution to consider in the years ahead.

“Urine,” he says, “contains a high proportion of important nutrients that plants need. As urine is usually pathogen free and low in heavy metal concentrations, there is no doubt that it can easily be turned into a fertiliser, but with great caution in its application.”

Urine alone might not be enough

Mike Philpott, a recently retired analytical chemist from the Agricultural Research Council with several years of experience in chemical analysis of fertilisers, says farmers are likely to consider urine fertiliser as an option, assuming that it is cheaper than conventional artificial fertilisers.

Philpott does, however, question whether urine as fertiliser is better than what is readily available in stores. He believes urine is only a good source of one of the big three plant nutrients. “Urine is rich in only nitrogen, due to a high concentration of urea in urine. Urea has about 46% nitrogen, but tiny amounts of phosphorus and potassium.”

“Urine contains a high proportion of important nutrients that plants need.”

Therefore, urine alone would not be useful as a fertiliser unless the soil already has enough phosphorus and potassium, Philpott believes.

Another problem, he explains, is that human urine in particular has a fairly high concentration of NaCl (sodium chloride or ordinary table salt), which is bad for the soil. “This is probably less of a problem with urine from certain animals like cattle that probably have less salt in their urine.”

Fertiliser products must be registered

It is not clear to what extent Mzansi’s farmers are already experimenting with this method. However, in other parts of the world the use of urine has already been tested and evaluated as a crop fertiliser for small-scale farming.

Swedish researchers Prithvi Simha, Björn Vinnerås and Jenna Senecal have discovered how to recycle urine into valuable – and sustainable – farmland fertiliser. Their scientific output, according to a research article published by The Conversation, was a solid fertiliser containing 10% nitrogen, 1% phosphorus and 4% potassium – a similar combination to blended mineral fertilisers.

Also, in South Africa, a research team led by Dr Dyllon Randall of the University of Cape Town has already successfully developed a waterless urinal to produce fertiliser.

Meanwhile Vusi Mashele, technical assistant at the Fertiliser Association of Southern Africa (Fertas), tells Food For Mzansi that all fertilisers used or sold in South Africa must be registered. “For one to register urine as a fertiliser, producers would need to meet the fertiliser requirements as set on group 3 (fertiliser) guidelines.”

Group 3 fertilisers are natural or synthetic substances that improve the growth or yield of plants, or the physical, chemical or biological condition of the soil. It includes seaweed, organic acids, bio-fertilisers, fertiliser coatings and moisture absorption products.

On top of this, Mashele adds, “You will need to conduct trials showing that your fertiliser does not kill plants and perform a certain function as per definition of fertiliser.”