The benefits of using composted solid waste as a fertilizer are well known. But how many people also know that human urine is packed with valuable nutrients essential for plant growth? Regrettably, most of these nutrients are lost when they are flushed away into water bodies or landfills, never benefiting agricultural soil and often causing (ground)water pollution.
The majority of Nepal’s farmers rely on imported urea and phosphate fertilisers like DAP to fertilize their land. However, when you consider that mined rock phosphate is a non-renewable resource afflicted by record rates of depletion, the need to explore ways of recovering these lost nutrients from urine and recycling them to agricultural land becomes ever more urgent around the globe.. The workshop to present key findings of a two year research programme on struvite recovery from urine in Nepal was held in Kathmandu.
The project, named STUN (Struvite Recovery from Urine in Nepal) is a joint initiative between UN-Habitat and Eawag; the Swiss Federal Institute of Aquatic Science and Technology.
The team have been exploring a number of approaches, the first of which is ‘struvite precipitation, a method of extracting struvite (MAP or magnesium ammonium phosphate) from urine by adding magnesium to produce a safe bio-available powder fertilizer. This powder form has the advantage of being easier to transport than urine; it’s lighter and takes up less space, the nutrients can be stored over time and the lack of odour makes it a much more user-friendly product. The technology used in the process is simple and cost effective; the reactor used to produce struvite was built using only parts purchased in Kathmandu. Unfortunately with this process only a fraction of the nitrogen in urine is captured. To make a sustainable business out of urine treatment, a technology to capture and reuse this nitrogen will also need to be developed.
In case you’re wondering, urine can actually be applied directly to the field, so long as it’s diluted with water in a ratio of 1:3, to avoid a concentration of nutrients burning the plants. However, when applied with a bucket, what happens is that part of the ammonium volatilizes, meaning that some of the precious nitrogen nutrients are lost. One way to minimise the losses is to apply the urine with drip irrigation: the liquid flows through a set of hoses, and reaches the plants directly with the irrigation water. But, one ropani (5476 sq. ft. square feet) of land in just one sowing season would need almost 750 litres of urine!, This is equal to the amount that one adult and one child excrete together in a year.
So the challenge for farmers using urine is finding a way of acquiring enough urine. The project team explored various collection methods in their pilot village Siddhipur on the outskirts of the Kathmandu valley. A ‘urine bank’ was installed in Siddhipur and someone was employed to collect urine from houses in the village and transport it on a pee-cycle outfitted with two 20 litre jerrycans. (Finding someone who was prepared to overcome the stigma of transporting urine was yet another challenge!) Collection from larger institutions such as schools turned out to be the most efficient option by far.
The two year research project is now nearing its end, but it has definitely thrown up some interesting ideas. Recycling liquid waste to produce fertilizer from urine would undoubtedly improve sanitation if it were rolled out on a large scale. It could contribute to local food security; reversing soil degradation which is caused by imbalanced use of chemical fertilizers. As DAP is expensive many farmers rely on urea only, which leads to over fertilisation of nitrogen and depletion of other plant nutrients as phosphate and potassium. Enriched soil would yield better quality, organic produce which could possibly be sold at higher prices on the market. It could lead to nutrient independence, providing cheaper fertilizer for Nepal’s farmers currently reliant on chemical fertilizers imported at prices that are not always affordable, if at all available.
Acquiring enough urine is still an issue and for the idea to develop into a workable system, changes would need to be made at a policy level, creating, for example a policy whereby offices were required to supply urine to the collection system. Cost is also a factor; setting up the infrastructure needed would undoubtedly require a significant investment. Add to this the stigma associated with handling urine, and the hygiene education that would be needed, and it’s clear there is still some way to go.
In Kathmandu alone, 1 billion litres of nutrient-rich urine are currently being wasted each year, polluting our rivers and ground water – just think how many crop yields could be enriched if it were to be put to use!
Written by Anita Pradhan, Documentation Manager, WaterAid in Nepal and Yvonne Struthers