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Struvite and Terra Preta made of urine from ecosan toilets – students´ research with WECF and CAAW in Kyrgyzstan

Research on the feasibility of organic fertilizer production from human excreta

02.12.2014 |

Jasmin (middle) is interviewing an ecosan user

WECF and CAAW work currently with two students, Santtu Palokangas from Wageningen, the Netherlands, and Jasmin Barco from Hamburg, Germany, in the South of Kyrgyzstan, who are doing research on the feasibility of organic fertilizer production from the human waste of Ecosan toilets. Ecosan toilets or Urine Diverting Dry Toilets (UDDT) were introduced in the country eight years ago. The user acceptance of the toilets is high and many households also use the stored urine as a nitrogen rich liquid fertilizer in subsistence farming but in some areas the acceptance for urine use is limited.

In Osh, where the students work, more than 1500 people use the UDDTs which have been implemented in households as well as in schools. The students look now into the feasibility to treat the separately collected urine further with the struvite production, a dry mineral fertilizer formed through the addition of magnesium into urine, or terra preta treatment, a high quality soil as result of excellent waste management found in the Amazon. Santtu is focusing on the first and Jasmin on the latter. Both have interviewed UDDT users on the acceptance of their toilets and have interviewed farmers on their fertilizer needs in order to see if the production of these products would be a success in Kyrgyzstan.

Struvite is a mineral that contributes to closing the nutrient cycle. Struvite can be produced as a result of a relatively simple chemical reaction from human urine and other nutrient containing liquids. Magnesium is added to urine at pH 9 conditions and mixed. As a result, a reaction occurs where the added magnesium reacts with ammonia and phosphate ions present in the urine. The resulting product is a stable crystalline mineral that has a potential value as a fertilizer in agriculture. The struvite reactor can be a simple and low cost option as a home manufactured fertilizer. Building a struvite reactor from locally available materials with lowest possible costs is currently being studied in Kyrgyzstan.

Terra preta is very similar to composting, with the exception of the addition of some ingredients, most important charcoal or biochar. There is no set recipe for terra preta production since the original way of producing the high quality soil has been lost. Scientists however have studied the products’ characteristics and it has been determined that lactic fermenting bacteria, charcoal and human excreta are indeed a part of the original mix. Jasmin is now working on producing a Kyrgyz version of terra preta with local available materials.

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