EcoEng Newsletter 3, December 2000 

Innovative Ecological Sanitation Concept Shows Way Towards Sustainable Urban Development

By EcoEng-Correspondent Almut Hoffmann, Germany



Combining good living and environmentally sound engineering

In Vauban, a suburb of Freiburg, Germany a new model house was built in 1999, which combines highly innovative energy, waste and sanitary concepts with a framework for a comfortable social environment.
Due to the energy concept, residents need only 20 % of the primary energy (electricity and heating energy) used in a conventional house. All energy saving investments are strictly controlled by the ratio of cost to efficiency. The costs are only about 7 % higher than in a conventional house and amortize over 10 - 20 years, which makes the house affordable for average German citizens.
Figure 1: Experimental house in Vauban district, Freiburg, Germany
Hot water consumption is 100 % provided by a thermal solar installation (in summer, and supplemented by a small co-generation plant, using natural gas, in winter. Electricity is provided by a photovoltaic device 60 %. Optimal insulation, the utilization of active and passive solar energy, the triple-glass windows and a 80 % reduction of aeration heat loss save 85 % of the heating energy over the year, compared to a conventional house.
Table 1: Technical data
thermal solar installation 46 m2 
co-generation plant
total heating efficiency
heat consumption
5,5 kW electr / 12 kW thermal
60 %
5.148 kWH/a
photovoltaic device 3 kWp
triple-glass windows k-value 0,7 / g-value 0,6*
dwelling and effective space 1.529 m2 
heating energy consumption 13,2 kWh per m2 and year
hot water consumption 23.408 kWh per year

*: g-value is the percentage of global radiation that can pass a window pane 


Sustainable water management

A combined vacuum sanitation system was implemented in the model house. Biological waste, feces and urine (so-called "black water") are transported from the water saving vacuum-toilets to a biogas reactor with vacuum pipes. The reactor produces liquid fertilizer as well as biogas used for cooking. The remaining wastewater from kitchens and bathrooms (grey water) is used again after it has been cleaned in aerated sandfilters and treated with UV-rays. Rainwater flows through open gutters and is collected in two ditches. The two ditches are connected to the groundwater strata with packages of gravel, so the rainwater is filtered before reaching the groundwater.
 Figure 2: Scheme of the ecological sanitation concept (show in detail, 143 kB)
A detailed ecological comparison of conventional and sustainable water management showed the folowing reduction of waterconsumption and emmisiions into water : water consumption is reduced by about 50 %, carbon emissions by about 70 %, nitrogen, phosphorus and AOX (absorbable, organical halogens) emmisions by about 90 %, 60% and 48%, respectively, and copper emissions by 47%. The seperate treatment of grey and black water and the recycling of nutritives to agriculture could be an energy efficient and longterm solution for water management.


Jörg Lange
Walter - Gropius - Str.22
D-79100 Freiburg
URL: http://, "Wohnen & Arbeiten" [in German]
© 2000, International Ecological Engineering Society, Wolhusen, Switzerland