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Student term project 2006:
Assessing the Flintenbreite Housing Estate in Luebeck, Germany

Students of Environmental Engineering
University of Applied Science Zurich
Dep. Life Sciences und Facility Management

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During our studies in ecological engineering at the University of Applied Sciences Waedenswil, Switzerland (HSW) we evaluated examples of eco-design. "Flintenbreite" is the case study of our group.

"Flintenbreite" is an ecological housing estate built in Luebeck, Germany. It contains 117 apartments in semi-detached houses, terraced houses and blocks of flats for up to 380 inhabitants [1].

"Flintenbreite" is a project for ecologically and economically sustainable urban development. Firstly, there is a special wastewater concept. The housing development has a wastewater system in which blackwater (faeces and urine) and greywater (wastewater from the kitchen and bathroom) are treated separately. The blackwater is transported to a central anaerobic digestor. There it is, together with the organic waste from the households, converted into biogas, which can be used for power and heat generation.

The greywater is fed into the wetlands, constructed as vertical flow filters, from where it flows into a pond and can be used for irrigation. The rainwater from roofs and sealed areas is collected and infiltrated into the ground. Other technologies used in the project are vacuum toilets with very low water consumption, solar panels for wa-ter heating and an adapted ventilation system. Finally, the settlement is constructed only with ecological material [1].

Criteria

To evaluate the project, nine criteria of Heeb 1994 (as cited in [2]) were applied. Those criteria have been selected because they are objective and include more or less all aspects of good eco-design.

Heeb in van Bohemen [2] formulated the following criteria. A good eco-design should:

1. follow a "begin-of-pipe" thinking (that means to treat the problems at the be-ginning)
2. be system-oriented, sustainable and multifunctional
3. use simulated and modified ecosystems
4. use and create system solutions,  look for high system integration and promote self-stabilization
5. keep energy and resource consumption low, use solar-based energy sources and promote recycling
6. look for natural design and a high degree of integration into the landscape
7. keep the impact on the environment and the potential of risks as low as possi-ble
8. combine knowledge and experiences from different disciplines
9. promote decentralized structures, non-dependent systems and long-term thinking.

Evaluation

Criterion 1

The first criterion proclaims a "begin-of-pipe" thinking, which a good design should follow. Flintenbreite fulfils this cri-terion. Especially the wastewater system clearly follows this thesis. The different water fractions are collected separately [3]. The houses are built in a way that is more strict than the low-energy-consumption-standards of the State [1]. Therefore the construction of the buildings minimizes the use of energy, especially for heating. The electrical energy used in the development is distributed through a central account system. Energy-saving behaviour is rewarded with less renting costs. This helps to minimize the use of electricity.

Criterion 2

The wastewater system of Flintenbreite is not only a discharge system but also produces electricity and heat in the biogas plant. Furthermore the nutrients are brought back to the production cycle by using it as an organic fertiliser on the fields. This shows the multifunctional way in which the system operates. The system is divided into separate parts, which only run efficiently in combination with each other.

Apart from the quite high need of energy for the running of the vacuum-toilets, the water treating systems run on a low energy input compared to conventional treatment systems. Additionally, the use of blackwater and organic waste for energy production reduces the need for energy from non-renewable resources even more. This is a clear demand of sustainability [4]. On the other hand, the use of drinking water for toilets and washing machines does not fulfil the criterion of being sustainable. Criterion 2 is therefore only partly fulfilled.

Criterion 3

An imitated ecosystem is used to clear the greywater from bathrooms and kitchens. It flows through a constructed wetland, where the plants absorb the nutrients.

The biogas plant, which uses bacteria for digesting organic waste, is a highly modified ecosystem, which doesn't rexist like this in nature. The question may be justified, if it can still be called an ecosystem.

The construction of the housing estate does not especially follow an imitated or modified ecosystem. Therefore we rate Flintenbreite as partly fulfilling criterion 3.

Criterion 4

The fourth criterion evaluates the inte-gration and self-stabilisation of the system. In Flintenbreite the different parts of the wastewater system are integrated. The system itself is integrated into the housing development. In addition, the energy and nutrient flows are connected to the surroundings.

The housing estate operates semi independently from the city's energy supply. But the system wouldn't work without the input of man, especially the biogas plant.

We rate criterion 4 as partly fulfilled as the system is highly integrated but does not work for itselfü the aspect of self-stabilisation is not fulfilled.

Criterion 5

At first sight Flintenbreite fulfils criterion 5. Saving energy is partly evaluated in criterion 1. Houses built according to low-energy-consumption-standards are efficiently insulated and use the sun for heating e.g. through the windows.

The sun's energy is also used in the constructed wetland, where the plants absorb the nutrients.

Nutrients in blackwater and organic waste are recycled as organic fertilizer and the energy is used in the biogas plant.

To evaluate criterion 5 in detail further information would be needed.

Criterion 6

The integration of the settlement into the landscape is difficult to estimate with the available information. Moreover, the question of good design is a matter of personal taste. Nevertheless our try: the location plan shows soft boundaries around the housing estate, which covers an area of 5.6 ha. 2.1 ha of it are left as natural green space [1]. Architectural guidelines were set up for the construction, so as to minimize the sealing and maintain a responsible use of ground.

We rate criterion 6 as fulfilled, as the construction of Flintenbreite pays attention to natural design.

Criterion 7

The impact on the environment is kept very low at Flintenbreite and therefore fulfils criterion 7. Especially the treatment of wastewater is fully integrated into the settlement. The outflow consists only of clean water. The houses are built using only ecologi-cally friendly construction materials of high quality. Flintenbreite uses the climatically neutral biogas from the integrated biogas plant for heating. Natural gas is used for additional heating only if required.

Criterion 8

The construction of the settlement combines knowledge of architecture, engineering and ecology. Low-energy-consumption buildings are the output of this synergy. Furthermore, the wastewater treatment with its biogas plant is a highly sophisticated system, which combines ecology and engineering [5]. From this point of view Flintenbreite fulfils criterion 8.

Flintenbreite is independent from the public wastewater system as well as mostly independent from the town's energy supply. The modular construction of the energy centre enables the extension of the housing development. With this long-term thinking and the decentralized structures Flintenbreite fulfils criterion 9.

Possible improvements

Today the rainwater is collected in this settlement and directed to the grassland for infiltration. This is a good opportunity to protect the purification plant from unnecessary water. In order to use the water more effectively, this water could be collected in a tank and be used for different purposes, for example for the irrigation of gardens or, depending on the quality, also for use in washing machines or similar. Additionally, the treated greywater could also be directed back into the water supply of the bathrooms.

In addition, an integrated farm, which would cultivate the land  surrounding this set-tlement in a sustainable way, would also be a good opportunity to adapt the hous-ing estate even more to the countryside. In a small village-shop this farm could supply a large part of the housing estate with vegetables and other organic products. Additionally, this farmer would also supply more biomass to the biogas plant to in-crease the locally generated electricity supply.

Finally, it would also be imaginable that the biogas plant could digest all the organic waste of the city and produce even more energy.

In conclusion, rated by this evaluation Flintenbreite is a good example of ecological design. Nevertheless it still has some potential for improvement.

References

[1] GTZ Datenblatt (2005): http://www2.gtz.de/ecosan/download/ecosan-pds-004-Germany-Luebeck-Flintenbreite.pdf (9-14-2007)

[2] Ecological Engineering - Bridging between ecology and civil engineering, Hein van Bohemen (editor), Aeneas Technical Publishers, Delft, 2005

[3] Integriertes Abwasserkonzept: http://www.otterwasser.de/german/konzepte/flintg.htm (in German, 9-14-2007)

[4] Homepage Flintenbreite: http://www.flintenbreite.de/ (in German, 9-14-2007)

[5] Steckbrief Siedlung: http://www.oekosiedlungen.de/flintenbreite/steckbrief.htm (in German, 9-14-2007)