Pee for plants

Experiments explore the potential of urine as fertilizer
Pee for plants

On the outskirts of Kathmandu, Siddhipur village has rediscovered the value of urine. More than 100 toilets in the village divert urine to farms, where it is used as fertilizer. It is not a new practice, though. The village was recycling urine before modern fertilizers were introduced. “In the past, people would urinate in a pit of ash and rice husk under their staircase. They would then use the composted material as fertilizer,” said Jiban Maharjan of Siddhipur.

An enterprising farmer, Maharjan is among the first few in the village who started using urine six years ago. That was the time when Kathmandu ngo Environment and Public Health Organization that promotes ecological sanitation—ecosan in short—had introduced toilets segregating urine and faeces in the village. Maharjan asked the ngo to instal an ecosan toilet in his house. He said the potato yield of his plot is equal to what his neighbour gets from six times as much land. In his experience urine also makes vegetables larger and more resistant to pests.

By improving yield and reducing use of synthetic fertilizers, urine can bring additional profits to the farmer. An experiment at an Indian village showed how. Farmers at Musiri in Tiruchirappalli district of Tamil Nadu collect urine from a community ecosan toilet and use it as fertilizer for 750 banana plants. The experiment started by the National Research Centre for Banana (nrcb), in collaboration with scope, a non-profit in the region, has generated data over five years that shows one can make an additional profit of Rs 45,175 per hectare by using urine. Of this, Rs 36,250 is due to increased bunch weight and Rs 8,925 saved on synthetic fertilizers, said M M Mustafa, director of nrcb.

Using urine as fertilizer, though, has its limitations. “It is misleading to say it is a complete solution,” said Madhab Nayak, president of the Fountain of Development Research and Action, a Delhi-based ngo that has tried promoting use of urine in farms in a Ghaziabad village (see ‘Collector’s item’, Down To Earth, November 16-30, 2008).

Sufficient nutrients?

Nayak has compared crops’ nutritional requirements with urine’s nutrient content. According to the Handbook of Agriculture, the most authoritative publication on Indian agriculture by the Indian Council for Agricultural Research, a one-hectare plot requires 80-120 kg of nitrogen, 60 kg of phosphorous and 40 kg of potassium for growing wheat. Nayak explained that urine, though rich in nitrogen, fails to meet the demands for the other two macronutrients during the first application. But in the second and third application neither phosphorous nor potassium is needed. Using urine for the second and third time amounts to excess fertilizing, he warned.

M Subburaman, director of scope, experimenting with urine fertilization in Tiruchirappalli, said the trick lies in getting the nutrient combinations right. This was possible since his team tested the nutrient content of the urine supplied along with the nutrient requirement of a banana plant per season (see table). “We found that while urine was meeting the nitrogen and phosphorous demands, lack of potassium was affecting the plant height and pseudostem girth,” Subburaman said. His team supplemented urine with 75 per cent of the recommended dose for potassium. “We recorded the highest bunch weight with this combination,” he added.

The right practice

How one applies urine is also crucial. To avoid the risk of microbial infection one must take care that urine is not mixed with faeces and is applied 10-20 cm from the plant, said Helvi Heinonen-Tanski, professor at the department of environmental science, University of Eastern Finland. There could be some risk if the urine contains antibiotics— soil bacteria can become resistant to antibiotics and pass on the resistance to bacteria infecting people—but this is hardly the case, said Tanski, who has written academic papers on the use of urine as fertilizer.

To make sure it is free of microbes, urine collected at the community toilet in Musiri is made to pass through sand and charcoal filters and stored in a tank for a week. who guidelines say no storage is needed when urine is collected from household ecosan toilets that segregate faeces and urine, as in the case of Maharjan, or when the user ensures the urine is not contaminated by faeces and by others’ urine. Urine originating from ecosan community toilets should be stored for at least a month before use.

Urine can be applied diluted or undiluted, depending on the soil and crop. Mixing urine with water reduces the risk of wilting and excess fertilization, while crops get irrigated at the same time. “For each banana plant we found that applying 10 litres of urine mixed with 100 litres of water five times a year gave the best results,” said Mustafa.

Maharjan devised his method of applying urine through trial and error. Inspired by a workshop on urine use organized by the Kathmandu ngo, he began his own experiments on vegetables, fruits and flowers. Over six years he found applying urine two to three weeks before sowing is best. He would furrow a line at the site where the seed is to be placed, apply undiluted urine and cover with dung mixed with soil. Two litres for a length of six feet is sufficient for potato, he said. Once the saplings appear he applies urine (diluted to a ratio of 1:3) three more times.

Best for densely populated areas
If Maharjan can benefit from urine why not all farmers? What holds back the use of urine on a wide scale is the logistics of collection and transportation. “For instance, growing rice on a hectare needs 10,000 litres of urine for the first application. This means connecting toilets of over 100 families to a plot of this size,” Nayak said. So high density of population is essential. Nayak says urine fertilization schemes must target peri-urban areas within two km of the point of use.

In Musiri village, the banana plantations are two km from the community toilet. Each week 250 litres are transported to the field. Since April bullock carts have replaced cycles for transportation. It could be easier still. One way to escape lugging urine is to convert it into struvite, white and odourless powder formed when magnesium is added to urine. Struvite takes up less volume and is lighter than urine. It is easy to store and handle. Eawag, the Swiss Federal Institute of Aquatic Science and Technology, in collaboration with un - habitat Nepal, chose Siddhipur to assess the feasibility of converting urine into struvite. The project—Struvite for Urine in Nepal (stun)—is the first example of in situ production of struvite in a developing country.

A stun report says struvite, or magnesium ammonium phosphate, contains 6 per cent nitrogen and 29 per cent phosphate. The most efficient source of magnesium is bittern, the waste product of salt making available for free in India. Subburaman plans to use struvite and discard bullock carts in the long run. Making struvite in Nepal costs more because bittern has to be imported. Another source of magnesium in Nepal is magnesite from mines in Dolakha.

stun’s calculation shows struvite can generate in Siddhipur will be much less than than the village’s demand.

Can urine go commercial?
“We could do so much more, if only we had more urine,” Maharjan said. He is lucky his neighbours, who have urine-diverting toilets but no farms, are providing him their urine. stun research coordinator Bastian Etter is clear where to focus. “Where we see the potential for struvite is in the city,” he said.

There are some who do not agree. “For experimental and academic exercise it is fine, but there is little scope for commercial use,” said U S Awasthi, managing director of the Indian Farmers Fertiliser Cooperative Ltd.

Synthetic fertilizers are subsidized by the government—for 2010-11 it is projected to be Rs 50,000 crore. But urine use is not recognized by the Fertilizer Control Order issued by the Indian agriculture ministry to provide for price, quality and quantity control.

In Nepal, stun is not ready to give up. It is launching two projects within a month to promote sustainable use of urine. In Siddhipur a urine bank is under construction. The second plan is to make struvite on a larger scale.

Related Stories

No stories found.
Down To Earth