Aquaculture Europe 2023

September 18 - 21, 2023



 The goal of the BlueBio co-funded  SIDESTREAM project was to evaluate new ways of recycling aquaculture and agriculture wastes to save resources and create value.

Aquaculture and agriculture produce vast amounts of wastes . The SIDESTREAM project regards these wastes as ’side streams ’ and considers them a resource . We investigated to which degree marine organisms such as polychaete worms and gammarid shrimps , and also bacteria can be utilised to recapture nutrients , energy and biochemicals from side streams . Furthermore , we evaluated the suitability of the biomass as a fish and shrimp feed ingredient . Finally , we evaluated the sustainability and economic feasibility of these activities.

 All side streams used as feed input for the projects model species were utilized as feeds , in some cases (e.g., liquid phase biogas side streams for bacteria ) pre -treatments were necessary . Rearing protocols for the marine polychaete Hediste diversicolor , the gammarid shrimp  Gammarus locusta , and the genetically modified Corynebacterium glutamicum have been established . These protocols have been developed to optimize biomass production , resource utilization and production of high nutritional value fatty acids (gammarids and polychaetes ), and astaxanthin ( C. glutamicum ).

During the project we learned how to treat these biomasses to process and stabilize valuable compounds . Further, polychaete , gammarid and bacterial meals were formulated into fish and shrimp feed and tested for their suitability as replacement of either fish meal or fish oil , or as attractants.

 Juvenile sea bass (Dicentrachus labrax ) thrived on diets replacing 10%, 20%, or 40% of the fish meal with polychaete meals . None of the fish fed polychaete meals differed in growth , feed conversion , or protein digestion efficiency from those fed commercial sea bass diets .

 Juvenile rainbow trout fed diets containing astaxanthin produced within the project showed less appetite for the diets compared to trout fed diets containing commercially available astaxanthin sources , which was also reflected in reduced growth rates . However , it shall be noted that the astaxanthin produced in the project was used as autoclaved bacterial biomass , not as extracted pigments , which clearly differs from using synthetically produced astaxanthin , and the result is hence to be treated with caution .

 LCA analysis revealed that electricity and water usage is a main driver of costs and decreased sustainability when biogas digestate shall be used as feed input . The reason for this is the high ammonia content which needs to be removed from the solid phase . LCC comparing a high-tech and a low-tech scenarrio revealed that scaling effects in the low-tech scenario by far exceeds those in high-tech scarios . LCA on polychaete meals as a fish meal replacer revealed that suggests that the circular approach of rearing polychaete on aquaculture wastes activities may reduce the environmental impact by 23% as opposed to a linear approach.

 SIDESTREAM covered several steps along the value chain – from biomass production to the provision of products through conversion and processing . SIDESTREAM enhanced our knowledge on the ability of invertebrates to produce high value compounds . The project lead to novel and refined production techniques and protocols leading to increased production of these compounds under highly controlled conditions .