Full-scale site solution of phosphorous retrieval from biowaste

• The Baltic Sea suffers from eutrophication and one major effect is that seaweed and algae accumulate in large volumes on beaches along the sea. The seaweed and algae undergo partial decomposition which constitutes a major obstacle for usage of the beaches for bathing and other recreation.  The costs for removing the seaweed and algae in order to make the beaches available for tourism and recreation are substantial, but the benefits from tourism greatly exceed the cost for removing the algae. Additionally, the removal of the algae also brings about important environmental and social benefits since the phosphorous, cadmium and nitrogen in the algae are extracted from the Baltic Sea. The removal of algae also makes coastal areas available for spawning fish and other organisms by improving the availability of oxygen. When decaying, algae also contribute to high emissions of methane, which would be reduced if the algae are removed. The initial idea of this project was to digest the sampled algae in a fermentation plant. The intention was to achieve recycling of the phosphorus while eliminating the cadmium content. During the project it was concluded that this is possible but not viable. This is carefully elaborated in the appendix “technical feasibility and ecological assessment”. The PhosCad project has investigated and examined the most cost-efficient solutions for removing the algae, recycling the phosphorous, reducing the level of cadmium and utilizing the residue for production of biogas and as fertilizer. The business plan framework is based on the results from the technical feasibility and ecological assessment report and presents the motives for removing the algae from a municipal business perspective. The municipality of Trelleborg functions as a case study since detailed information concerning beach related tourism and cost for removing algae is available for this city. Drying, incineration and ash disposal , with partial drying and incineration for district heat and electricity, is considered to be the most viable way to handle the material. The project benefits, including municipal tax revenues from beach related tourism and environmental benefits substantially outweigh the project costs, i.e. costs for drying, transport, incineration and ash disposal. All costs and benefits are rough estimates and not all cost information is available, and needs to be further investigated in a fully elaborated business plan. The increase in algae blooms have resulted in empty beaches and reduced beach tourism all around the Baltic Sea. The suggested method, Drying, incineration and ash disposal, is most likely of interest to many other regional and local governments around the Baltic Sea, at least as interim measures until more far reaching measure are implemented to improve the marine environment in the Baltic Sea.  

• This report is only available in English.

Nyckelord

Algae

cadmium

phosphorous

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vet (ämneskategori)

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