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Productive On-site Sanitation System: New Value Chain for Urine Based Fertilizer

Globally, it is estimated that 64% of the population are discharging human excreta, fresh or with flush water, into the environment without any prior treatment (Baum et al., 2013). Untreated excreta that enters the environment not only threatens people’s health but also leads to eutrophication and degradation of aquatic ecosystems due to the nutrients in human excrement being the same essential nutrients for plant growth: nitrogen, phosphate and potassium (N-P-K) (Jönsson et al., 2004). The main objective of the cartridge based sanitation system is to design an on-situ sanitation treatment system that would contain, treat and concentrate excreta and output a dry, commercial, fertilizer. The toilet functions as follows: the urine-diverting seat would channel the urine into the alkaline cartridge which would rapidly increase the pH of the urine to above 10 by ion exchange to limit the enzymatic-hydrolysis of urea. Next, the urine would flow to the dehydration cartridge which would contain ash (5% w/w) to insure high pH (>10) and act as an adsorbance medium during dehydration by ventilation (9 m3 hr-1). The dehydration module would be solar heated to reach average temperature of 35ºC (maximum peak temperature 40ºC). By diverting the urine away from the faeces, simpler treatments for the drier faeces maybe implemented – this is not part of the scope for this grant application. The objective is to prolong the retention time to minimize risk of handling and maximize natural decay rates. The cartridges will be designed to service a family of five and functioned to reduce the mass of excreta by >90%. There are four main activities. • Activity 1 is the development of urine treatment system: alkaline cartridge and dehydration cartridge • Activity 2 is the evaluation of survival rate of pathogens within the system • Activity 3 is the field trial of the full scale system in Uganda and South Africa • Activity 4 is plant trial with the concentrated urine produced from the toilets Based on preliminary results, the alkaline and dehydration cartridges would achieve 90% mass reduction of the urine within 24 hrs, while preserving 70-90% of nitrogen as urea. Odours would be limited by minimizing ammonia emissions and having negative pressure within the toilet. The final output from the urine would be a dry powdered fertilizer with a N-P-K mass percent of 9-3-11 – a concentrated, stable, storable and bag-able fertilizers, with a potential commercial value of 290$ per metric ton (USDA, 2013). This correspond to a value of 52 $ UDS for a family of five if all the nutrients would be collected (this value is based on world market price and local prices can be higher due to transport and retail addition or lower due to governmental subsidies). The installation costs of the toilet are estimated to be more than a VIP latrine and less than twin-pit or pour-flush system. The annual material costs are estimated at 30$ USD a year (only material costs were considered, as labour costs vary greatly). Overall, the risk for disease transmission from the system would be minimal due to the elevated pH and low moisture content. The true innovation of this cartridge based sanitation system is that no highly mechanized treatments or monitoring systems are required which otherwise can inhibit the use of improved sanitation systems. By dehydrating the urine within 24 hrs, there would be no liquid disposal. Therefore, there would be no need for vacuum trucks or other complex, potentially, unsanitary manual emptying, making this sanitation system suitable for areas where mechanical emptying by service trucks is not possible.

Project ID

SE-0-SE-29-2015-03072-285-31182

Activity status

2 - Implementation

Aid type

D02 - Other technical assistance

% to Uganda

100.00

Organisations

Funding

Sweden

Extending

The Swedish Research Council

Implementing

Swedish University of Agricultural Sciences

CRS code	%
Agricultural research (31182)	100.0