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The Trelleborg Concept


Detailed description of the Good Practice

The municipality of Trelleborg together with local farmers and landowners, will establish large-scale biogas production based on new wetlands established along the coastal zone of southern Sweden. Growth and harvesting of reed belts and submerged vegetation will take place within these wetlands. Trelleborg municipality will use the biogas for transportation fuel, heating of domestic houses in urban areas and local production of electric power.

Climate change mitigation
Preventing eutrophication

Objectives of the Good Practice

The Trelleborg Concept of transforming a problem into a resource by preventing eutrophication through biogas production has a number of benefits for the environment in the region, but also has a global perspective:
• Biogas means less CO2 and is thus an important contributor to decreasing climate change.
• The establishment of wetlands will stimulate biological diversity in the region and will deal with the nutrient load from surrounding farm land.
• Harvesting of the reed belt will remove the nutrients from the wetland area.
• Harvesting of macro algae will remove nutrients and heavy metals from the Baltic Sea and improve local beaches for recreation purposes.
• The removal of Cyanobacteria will remove nutrients from the Baltic Sea, but perhaps the most important contribution is that it will improve recreational value in the region.
• When the shallow coastal waters are cleansed from oxygen-depleting, decaying accumulated macro algae, large areas will again become available to sustain the growth of juvenile fish.

Participants of the Good Practice

  • The municipality of Trelleborg
  • Local farmers and landowners

Funding of the Good Practice

Part-financed by the European Union in the context of the Baltic Master-project

More Details of the Good Practice

The nutrients reaching the coastal waters of the southern Baltic Sea from variety other sources, e.g. farming, traffic or sewage treatment, and from other geographical areas will be removed with new technology for collecting macro algae from the sea. The biomass collected will be used for biogas production.
The digestor residues from the biogas plant can contain heavy metals but there are existing techniques to remove these metals from the residues, which can then be used as fertiliser on arable land, resulting in nitrogen and phosphorus recycling.

During summers with extensive blooms of Cyanobacteria, surface accumulations of Nodularia spumigena will be harvested and used for biogas production. However, the residues will not be suitable as an agricultural fertiliser since they may contain toxic substances.

In addition to the establishment of wetlands in the coastal area and harvesting of algae, aquaculture of the blue mussel Mytilus edulis may be a way to indirectly remove nutrients from the Baltic Sea. Mytilus edulis is very efficient at filtering and removing micro algae from the water column. Several successful trials of
this method have been conducted on the west coast of Sweden, but may also be useful in the Baltic Sea. Although the mussels produced in the Baltic Sea will be too small for human consumption, it may be possible to produce biogas from them. In extending the concept of using these successful bio-engineering
techniques, the possibility of intentionally growing algae for harvest within metal frames in selected remote coastal waters with low leisure and ecological values is being investigated.

All these new means to remove nutrients from the highly eutrophied Baltic Sea in a low-intensity but steady process could bring about a much needed reversal in nutrient flow if they were to achieve widespread use among the member cities of the UBC.

Documentation and documents

Available files

Contact details

Municipality of Trelleborg
Mattias Müller
E-mail: mattias.muller@trelleborg.se

Data sources and references

Baltic Cities Environmental Bulletin 2/2008