The raw material used in Baltic Sea case study is fish waste i.e. salmon heads, bones, collars, cheeks, spines and bellies) coming from the fish filleting companies. These are combined with food waste coming from restaurants, tree leaves/common reed straw and ash, in order to optimize the fertilizer qualities and cost price of the final product, as well as to facilitate the functioning of the technology Initially, fish sludge was also tested, but later excluded due to low dry matter content 0.5%. Also, the initial use of oil shale ash had to be exchanged to wood burning ash, as EU legislation does not allow the use of former in organic farming. With the help of Estonian Crop Research Institute, physico chemical composition, contaminants and microbiology of the side streams were analyzed. The results showed that all raw material side streams were safe to use in organic farming, i.e. they all were within the allowed range of pathogen microorganisms, heavy metals and pesticide residuals. They all provide complementary nutrient content for fertilizing purposes. It was also found out that tree litter is preferred over common reed straw due to its beneficial fungi and optimal C/N ratio.
Since Baltic Sea case study uses bokashi fermentation technology, which significantly lowers the pH level of the product, adding ash was found to be beneficial for neutralizing this effect Combining fish waste with tree leaves and restaurant waste reduces the strong unpleasant odor of the fish waste fermentation.
Fig 1 and 2: Side streams from the left: fish waste, tree leaves, ash, restaurant food waste.
Further information: Video
Authors: Nutriloop OÜ
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