Category: Calculation

Faeces Application:

Faeces are rich in phosphorous (P), potassium (K) and organic matter and can contribute to non-food crop production both by their fertilising effect and by their soil-improving effect. The proportion of nitrogen that is in mineral form in faeces varies largely between the different purification strategies and can be lost in form of gases. Therefore, only the Phosphorus-fertilisation of Terra Preta Sanitation compost is considered.

Please find more information in this literature review.

Please Enter The Number of Household Members:

Yearly Faeces Production
per Household (kg/a):

Yearly Phosphorus-Fertilisation Area of Terra Preta Sanitation (TPS) compost per Household (m²/a):

Yearly Organic Content Supply Area of  TPS compost per Household (m²/a):

Urine Application:

Urine contains four important nutrients for plant growth: nitrogen (N), phosphorus (P), potassium (K) and sulphur (S). The direct application of nutrient-rich sanitised urine to the soil for non-food crops provide the opportunity to recover the nutrients and also reduce the use of fertilisers. The urine application calculator tool developed by RUVIVAL calculates the potential urine fertilisation area of a household based on the yearly production of urine.

Click On the Calculator Icon to Access the Urine Calculator

More information about urine application can be found here.

Background of the Calculator

Excreta Values	Values	Unit
Daily Faeces Production per Person	140	g/d	(grams per day)
Yearly Faeces Production per person	51.1	kg/a	(kilograms per year)
Yearly Amount of Nitrogen in Faeces per Person	550	g/a	(grams per year)
Yearly Amount of Phosphorous in Faeces per Person	183	g/a	(grams per year)
Phosphorus Fertlisation of TPS Faecal Compost per person	900	m²/a	(square metre per year)
Yearly Organic Content Supply Area of TPS compost per person	4.5	m²/a	(square metre per year)

According to Jönsson et al. (2004), the potential yearly amount of nitrogen and phosphorus in faeces per person in Sweden is 550 g/(a·person) of nitrogen and 183 g/(a·person) of phosphorus. The yearly amount of nitrogen and phosphorus in faeces per household is calculated from the potential yearly amount of nitrogen and phosphorus in faeces per person multiplied by the number of household members.

According to research done in Tanzania by Krause et al. (2015), total phosphorus in TPS compost is found to be 3.6 times the total phosphorus in faeces compost. The yearly faeces fertilisation area of TPS compost per household is calculated from the potential yearly fertilisation area of faeces per person (900 m² for phosphorus) multiplied by the number of household members. The yearly organic content supply area of TPS compost per Household is calculated from the potential yearly organic content supply area of TPS compost per person (4.5m² /(a·person)) multiplied by the number of household members.

This calculator takes as a reference point the research done by Jönsson et al. (2004), the amount and nutritional value of faeces and urine are based on the data of the Swedish population. It is important to note that amount and nutritional values of faeces and urine are subjected to variation in different regions of the world and are highly dependent on the nutrient uptake and diet of the population. The nutritional value of wastewater streams improves the quality of the urine and faeces to be used as fertilisers for non-food crops.  Therefore, the provided results should only be considered as a reference point when referring to the potential for nutrients recycling in integrated decentralised wastewater treatment.

The values used in this calculation tool are based on the following studies.

Jönsson, H, Richert, A, Vinneraas, B & Salomon, E 2004, Guidelines on the use of urine and faeces in crop production, EcoSanRes Publication Series, 2nd edn, Stockholm Environment Institute, Stockholm, Sweden.

Krause, A, Kaupenjohann, M, George, E & Koeppel, J 2015, ‘Nutrient recycling from sanitation and energy systems to the agroecosystem- Ecological research on case studies in Karagwe, Tanzania’, African Journal of Agricultural Research, vol. 10, no. 43, pp. 4039–5.

There is a computerized version of the USLE equation, named Revised Universal Soil Loss Equation (RUSLE). RUSLE is an improved formula, that can handle more complex combinations of tillage and cropping practices and a greater variety of slopes. A further-enhanced version the software is RUSLE2, which can do event-based erosion prediction. RUSLE2 requires a comprehensive set of input information, which may not be available in all jurisdictions.

The Water Erosion Prediction Project (WEPP) is a physically-based soil erosion prediction technology. It integrates hydrology, plant science, hydraulics and erosion mechanisms to predict erosion at the hillslope and watershed scale. It is capable of modelling and assessing a variety of land uses, climate and hydrologic conditions. It can be run offline on personal computers supporting Windows.

Total possible rainfall capture (m³/year) = Precipitation (mm/year) · Dimension of Catchment Area (m²)

If you would like to discover more about RWH methods, one fun and easy tool is to create a DIY rain-gauge to measure rainfall in your area, or take a look at a rainfall map of the world designed by NASA, to get a better perspective of precipitation levels worldwide. NASA is also looking for support from students, professors and science-enthusiasts, who would like to collect data and support their Global Learning and Observations to Benefit the Environment (GLOBE) Program. Moreover, if you need specific data on precipitation, the UN has created a large database that can come handy.

Rooftop Area by Claudia Lasprilla Pina is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Input the information provided in the tables above into the rainwater collection calculator, according to your region and rooftop material. The calculator will provide the solution to the following equation:

Supply of water in the storage tank (m³/year) = Rooftop area (m²) · Runoff coefficient · Precipitation (mm/year)