03.09.2007

Recycling nutrients saves the environment
Potatoes and cabbages fertilized with composted toilet waste includes also tests for taste in Tampere

In an environmental engineering research project of TAMK University of Applied Sciences potatoes and cabbages fertilized with composted dry toilet waste are taste-tested at the University of Kuopio. The fertilizer used was source separated urine and dry toilet compost collected from private households from Västanfjärd municipality. Prior to sowing these were certified to be microbiologically and chemically very safe to be used as fertilizers.

The testing of potatoes and cabbages cultivated in four differently fertilizer treatments includes also test for taste. High resolution image (572 Kb) Photo: Kalle Heiska

The potatoes are picked with care and the crop is stored carefully. High resolution image (474 Kb) Photo: Kalle Heiska

The preliminary results show that separated urine and composted human faeces are safe and efficient and environmentally friendly source of nutrient for crop plants. The efficient utilization of nutrients by crop plants and thus reduced nutrient leaching to the environment is beneficial, especially in developing countries, in the extensive domestic gardens of Eastern Europe and, for example, in the area between Stockholm and Gothenburg with its small amount of fresh groundwater.

TAMK University of Applied Sciences and University of Kuopio studied the microbiological quality and nutrient value of dry toilet compost and separated urine obtained from Västanfjärd municipality prior to planting Nicola potatoes and Castello white cabbages. The findings show that the urine and toilet waste used as fertilizers are microbiologically and chemically very clean as the levels of disease-bearing salmonella and coliform bacteria, for example, are clearly below the limits set for fertilizer products by the Ministry of Agriculture and Forestry.

The potatoes and cabbages were planted in early June in garden owned by the City of Tampere. The plants were cultivated in five different test squares using urine and dry toilet compost as such and as fifty-fifty for comparison. The amount of nitrogen in each treatment were for potatoes 80kg/ha, and for white cabbages 175 kg/ha.

The quality and quantity of the potato crop are already being examined in Kuopio and in Tampere. In addition to microbiological quality tests, the potatoes and cabbages will be tested for taste. The yield is ranked according to the taste in different fertilizer treatments.

This study on nutrient recycling on human excreta is unique by global standards. The representatives of TAMK University of Applied Sciences recently presented the research findings in China at the international conference Sustainable Sanitation: Eco-cities and Villages. Two students are writing their bachelor’s theses on the subject and in Kuopio the research is connected to two forthcoming doctoral dissertations.

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