In Norway the only available and processable sludge from fish farming effluent is in the dried form 90 dry matter), today available in approx 1000 tonnes / year In agreement with the other parties in our group we have decided to make two pelleted products from dried sludge A Pure pelleted fish sludge only. B A new organic fertiliser formulated with fish sludge as part.
From our tests with the treatment of raw fish sludge we have seen that bokashi treatment has not been successful. In fact natural bacteria develop in sludge (2% dry matter)and brings a natural pH drop. This may be caused by the fact that the sludge is continually produced, and during subsequent storage, bacteria colonise the sludge and lower the pH. These bacteria may originate from the fish farm itself If bokashi were to be applied in fish farming sludge treatment, one may have to dose it continually as the sludge is produced. This is beyond the scope of our study. Therefore we have moved forward with the ready available source we have got hold of, which is dried sludge, and made two alternative fertilisers. We have produced 200 kilos of each and sent samples as requested. The rest is stored for the coming growing field tests.
Further information: We have composed a fully organic fertiliser B, with our best knowledge of plant nutrition.
Expected content of B is 10 % N, 2.2 % P, 5.6 % K, 4.0 % S, 5.5 % Ca and 0.4 % Mg
Expected content of A is 6 % N, 3.5 % P, 5.0 % Ca, 0.1 % Mg and 0.5 % S
Authors: Grønn Gjødsel Lars Evju and Tommy C. Olsen
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