Aquaculture Europe 2021

October 4 - 7, 2021

Funchal, Madeira

Add To Calendar 07/10/2021 09:20:0007/10/2021 09:40:00Europe/LisbonAquaculture Europe 2021TOWARDS A CIRCULAR AQUACULTURE: THE CONTRIBUTION OF H2020 GAIN PROJECTLisboa-HotelThe European Aquaculture Societyalistair@aquaeas.eufalseanrl65yqlzh3g1q0dme13067DD/MM/YYYY



Hallstein Baarset1*, Christian Bruckner2 , Lars Svenningsson3, Johan Johansen4, Richard Newton5, Wesley Malcorps5 , J.A. Vazquez6 ,  Ricardo  I. Pérez-Martin6, Carmen G. Sotelo6 , Martiña Ferreira7, Leticia Regueiro7, Roberto Pastres8


Affiliations:1Waister , Norway; 2Salten Havbrukspark AS; Norway; 3 LS Optics AB, Sweden; 4 NIBIO,  Norway;  5 Institute of Aquaculture, University of Stirling.  UK; 6 Instituto de Investigaciones Marinas (CSIC), Vigo, Spain;

7ANFACO-CECOPESCA,Vigo , Spain , 8 Ca’ Foscari University of Venice, Italy




One of the main problems associated with any food production  value  chain is  valorisation of by-products and side-streams to reduce the environmental impact, while optimizing  the use of resources  (Newton et al., 2017) . This is especially needed for the aquaculture sector, where circularity principles are key elements to meet sustainability requirements .  In the  H2020  project "GAIN " , we have used different strategies to address this issue by investigating innovative processes aimed at reusing: fish sludge,  generated in Recirculating Aquaculture Systems (RAS) , fish mortalities,  by-products  generated  by  fish  processing (heads, frames and trimmings, skins, etc..), and shells from bivalves generated by the cannery industry . Main results and developments that will significantly contribute to the eco-intensification of this productive sector  are presented.

Material and Methods

As a basis for investigating and developing technolog ies for valorizing aquaculture side-streams we analysed wastewater from land-based Atlantic salmon smolt production farms for its chemical characteristics with respect to its environmental footprint and the underlying valorisation  potential.  To recover particulate, flocculated matters, the S3 filterdryer system was developed, including a fine meshed filter cloth (mesh size 6 µm) capable to remove particles from aquaculture wastewater. In addition, the S3 filterdryer sanitizes and dries the resulting sludge (DM content 91-94%) without the use of added chemicals (polymers, coagulants, etc.) . Besides, an alternative system, adding polymers and drying the  sludge  using the Waister superheated steam dryer to sanitise it, was also tested.

 For the sanitation of fish mortalities,  a new  superheated  steam dryer was developed, the Waister 15 generation.

In order to estimate the potential for valorisation of by-products ,  the  yield of these by-products in salmon, trout, seabream, seabass, turbot and carp were determined. These  by-products  were used as raw material for performing enzymatic hydrolysis to obtain fish protein hydrolysates (FPH).

 The suitability of bivalve shells for being used as filling material  of a newly designed biofilter for nitrification and phosphate  removal from RAS waste water was investigated. 10L volume biofilters were used at lab-scale level for compative experiments between plastic material  and crushed and  whole mussel shells. For phosphate removal experiments, crushed  shells biofilters were compared with calcite material,  the latter  simulating the abovementioned material calcined shells.


 The main challenge to purify aquaculture wastewaters lies with the very low levels of dry matter (DM) and the small particle size of solids present in  wastewaters.  The use of the newly designed S3 filtration system provides  a 93 + 2.8 % removal of suspended solids  (SS) and a 80 + 6.4 % removal of organic content determined as chemical oxygen demand (COD) in the treated wastewaters, confirming the utility of the S3 filter  dryer as a technology meeting the regulatory demand of a 50% SS  and a 20 % COD reduction as a standalone unit. The S3 system dries the sludge in parallel, achieving a DM content of 91-94%, without the use of chemicals and extremely low energy consumption: 300W per cubic meter wastewater for the entire process.

Sludge dried using  conventional heating, as  a  superheated steam dryer, resulted in a product with excellent physicochemical properties and DM contents of 90-95 %, outperforming airdried fish sludge as a bioenergy source in cement production. Analysis of dried fish sludge shows that it is an excellent bio-fertiliser product with high content of N and P, while low level of K. The Zn content is currently the most limiting element for allowed spead of dried fish sludge on farmland.

 Waister implemented a novel drying technology of mechanical fluidisation and superheated steam for sludge  of typically 10-50 % DM  from  polymer-based dewatering technologies. This technology can be combined with the S3 dewatering technology. Both systems stabilise the sludge and minimise shipping costs.

 Regarding the treatment of fish mortalities, a single loop Waister 15 dryer was installed in Helgeland Smolt, finalising a well-functioning technology for mortalites disposal. The main challenges with the treatment of salmon mortalities  were  the high fat content and the presence of excess water mixed with the fish. The first problem was solved with the incorporation of additives, such as wood chips or dried spent grain, while the second was solved with manual feeding of the fish into the dryer. The dried product obtained can be used for bio-energy production, biofertiliser, or potential animal feed ingredient  depending on the additive used prior to the drying.

The potential volume and economic value of by-products generated by the main aquaculture species in Europe was estimated.

Most by-products present a significant protein content : therefore, the  use  of  proteolytic enzymes to breakdown these proteins and use the resulting peptides for different applications, i.e. as ingredient of aquafeeds was investigated, in order to determine optimal operational, e.g. temperature, pH and other parameters.

Mussel shells were tested as a replacement for plastic filling in a RAS biofilter. Results suggest that mussel shells could be effectively used, as t hey provide  a suitable substrate for nitrifying bacteria and, due to their carbonate content, contribute to stabilize pH. Also, they  showed  interesting properties to remove dissolved phosphate from water, improving the quality of the effluent.


The research leading to these results has also received funding from the GAIN project, European Union’s HORIZON 2020 Framework Programme under GRANT AGREEMENT NO. 773330.


 Newton et al. 2014.  Perspectives on the utilization of aquaculture coproduct in Europe and Asia: prospects for value addition and improved resources efficiency. Critical reviews in Food Science and Nutrition 54(4): 495-510

 Morris, J. P., Backeljau, T., & Chapelle, G. (2019). Shells from aquaculture: a valuable biomaterial, not a nuisance waste product. Reviews in Aquaculture, 11(1), 42-57.

Newton et al. 2014. Perspectives on the utilization of aquaculture coproduct in Europe and Asia: prospects for value addition and improved resources efficiency. Critical reviews in Food Science and Nutrition 54(4): 495-510