An innovative technological approach is being evaluated for the valorization of aquaculture by products (fish sludge and dead fishes). The sludge is separated into solid and liquid fractions. Solid fraction valorization is conducted by applying the biodrying process, aiming to reduce the water content and obtain a nutrient rich biodried product to be used as an organic amendment It is also expected the combustion of this product to recover phosphorus from the ashes to produce phosphoric acid. The feasibility of recovering the volatilized ammonia during the biodrying to produce ammonium salts will be also evaluated in the project. Besides, in the case of freshwater aquaculture, dead Trout is used as co substrate in the biodrying process. The liquid fraction from sludge is being valorized by using several concentration processes. The approach in use, and also validated at the pilot scale, consists of an ultrafiltration (UF) system to separate solid particles present in the liquid fraction. The permeate produced by UF passes through the reverse osmosis (RO) system to concentrate the nutrients. The RO concentrate generated is subsequently processed in a Freeze Concentration (FC) unit, where the water is crystallized, and the nutrients are recovered in a nutrient rich concentrate product. Moreover, a high quality RO permeate with potential to be reused in the aquaculture industry facilities is also produced.

The technological approach used in the project evidences the feasibility of recovering the nutrients from dead fishes and the sludge produced in the aquaculture sector Hence, the technical solution proposed is considered a promising option for the production of bio based fertilizers from aquaculture by products.

Fig 1: Biodrying pilot unit for the valorization of fish sludge and dead fish
Fig 2: Technologies applied for the liquid fraction valorization

Authors: BETA Technological Centre (University of Vic Central University of Catalonia)
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