How much pooh?

Posted: October 22, 2012 in Uncategorized

Table 1 – Proposed Swedish design values for the mass of excrement (wet and dry mass produced per person per year) and concentration range of nitrogen, phosphorus and potassium excreted per person per year on dry mass bases (Kirchmann and Pettersson 1995; Höglund 2001; Vinneras 2002)

  Wet mass (kg) Dry mass (kg) Nitrogen (kg) Phosphorus (kg) Potassium (kg)
Urine 550 21 2.5-4.3 0.2-1.0 0.8-1.2
Faeces 51 11 0.5-0.7 0.13-0.5 0.1-0.5

The concentration of elements (see Table 1) in human excrement has diurnal fluctuations in individuals depending on dietary habits, hydration, perspiration, and level of physical work in the day (Heinonen-Tanski, Sjöblom et al. 2007). For example, a study in Sweden recently observed a 30% increase from the typical values of potassium in human urine probably due to the use of potassium supplement salt (Vinneras 2002). Cultures with higher meat consumption will urinate higher concentrations of nitrogen because of the increases protein content (Heinonen-Tanski, Sjöblom et al. 2007; Pradhan, Nerg et al. 2007).

These fluctuations challenge the designing process of waste management systems. Table 1 are the Swedes standard values of the mass of waste we excrete on an annual base. Nitrogen, phosphate and potassium (N-P-K, macro nutrients required by plants) by mass account for about 80%, 50%, and 60%, respectively, in domestic waste water, more than feces (Kirchmann and Pettersson 1995; Höglund 2001; Vinneras 2002; Ganrot, Dave et al. 2006; Mnkeni, Kutu et al. 2008).

 References:

Ganrot, Z., G. Dave, et al. (2006). “Recovery of N and P from human urine by freezing, struvite precipitation and adsorption to zeolite and active carbon.” Bioresource Technology 98: 3112-3121.

Heinonen-Tanski, H., A. Sjöblom, et al. (2007). “Pure human urine is a good fertilizer for cucumbers.” Bioresource Technology 98: 214-217.

Höglund, C. (2001). Evaluation of microbial health risks associated with the reuse of source-separated human urine. Department of Biotechnology. Stockholm, Royal Institute of Technology. Doctoral.

Kirchmann, H. and S. Pettersson (1995). “Human urine – Chemical composition and fertilizer use efficiency.” Fertilizer Research 40: 149-154.

Mnkeni, P. N. S., F. R. Kutu, et al. (2008). “Evaluation of human urine as a source of nutrients for selected vegetables and maize under tunnel house conditions in Eastern Cape, South Africa.” Waste management & research 26(132).

Pradhan, S., A.-M. Nerg, et al. (2007). “Use of Human Urine Fertilizer in Cultivation of cabbage (Brassica oleracea)––Impacts on Chemical, Microbial, and Flavor Quality.” Journal of agriculture and food chemistry 55: 8657-8663.

Vinneras, B. (2002). Possibilites for sustainable nutrient recycling by faecal separation combined with urine diversion. Department of Agricultural Engineering. Uppsala, Swedish University of Agricultural Sciences. Doctoral: 88.

 

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