Introduction
Optimization of feeding is a driver
to achieve the circular economy
in aquaculture. This will enable the enhanced utilization of nutrients and benefits the farming industry through improved production yields with reduced feeding cost, while minimizing the environmental impact of undigested and uneaten feed. Key criteria for the success and continued growth in aquaculture will be to accelerate innovations that can improve sustainable fish feeds, optimize the feeding efficiency, and provide advanced management control for different species in different rearing environments.
The challenge is to find alternative sources at a reasonable cost with the same or similar nutritional value, comparable palatability and digestibility and the potential to substitute fish meal entirely without any negative effect on growth and filet quality. To date, technological developments and commercial applications have mainly focused on algae as a micro-feed ingredient,. Moreover, there is a promise of much higher available quantities of algal biomass in the future (due to its development for use as biofuels), potentially serving the need as a bulk alternative to today’s feed ingredients for aquaculture.
Feed, being one of the major costs in fish production is also one of the major constraints for industry growth due to limited sources of sustainable raw materials. Further reduction of fish meal in feed for high value species (e.g. salmon, sea bass) and total replacement in diets of mass produced lower value species (tilapia, carps, African catfish) is necessary to make the world aquaculture more circular and sustainable.
The increase of circularity of the production system will be achieved by qualifying methods to obtain new and functional feed ingredients from algae and validating processes for optimal valorisation of waste and sludge from aquaculture production systems.
iFishIENCi is a European project that aims at delivering breakthrough innovations supporting sustainable aquaculture, based on enabling technologies and circular principles, thereby providing the European aquaculture industry with the competitive advantage and growth stimulation needed to be a mover in revolutionizing global efficiency in fish production and meet society’s needs for food from the ocean. The project targets circular principles and zero waste by qualifying new and sustainable organic value chains for feeds, and valorisation of by-products. In that sense, in the iFishIENCi
project framework, the waste water and sludge collected from the fish growth are used for algae cultivation, reducing th ose waste streams and gro wing algae for the production of new feed ingredients . Moreover, the project has actively contributed to the recommendations to incorporate the circularity into the aquaculture sector
(Policy Recommendations For a More Circular Aquaculture).
Material and methods
In iFishIENCI, the circularity associated to the use of waste streams from aquaculture to produce new feeds are addressed . To do so, available methodologies for circularity assessment are firstly reviewed and later adapted to measure the circularity along the value chain, focusing not only on feed production but also on the farming operation , where the nutrient assimilation plays a relevant role . With regard to feed formulation, ingredients sourced from waste valorisation routes are considered as recycled feedstock. The farming operation is also addressed since the efficiency of feeding is a key element in determining the functionality of the new formulations.
Three main indicators are defined for the circularity assessment of the new feed. Linear flow index (LFI) , Material circularity indicator (MCI) and Nitrogen waste indicator (NWi ) are the indicators that represents the circularity within the innovative aquaculture systems . The study considers nitrogen, as the principal nutrient involved in the bio recovery cycle.
Material Circularity Indicators of feed is defined in accordance with the Linear Flow Index of nitrogen together with a factor F(X) that is built as a function F of the utility X.
The utility
reflects the extent to which a product is used to its full capacity. In the context of IFishIENCi , digestibility is addressed in the circularity assessment though the ratio that
represents the Nitrogen assimilation efficiency (NE), calculated as follows:
The increase on
digestibility, that means the assimilation of nitrogen in feed, results in a more efficient use of any resources that take a linear path in the material flow. Therefore, the higher NE, the higher utility. It is calculated as the ratio between the NE of the new feed formulation obtained in the project in comparison with the NE average of the industry for conventional feeds and not-improved feeding systems.
In the example below, MCI is 58,93% higher when increasing nitrogen assimilation by 50%; MCI is 35,36 % higher when increasing nitrogen assimilation by 30 %; MCI is 15,69 % higher when increasing nitrogen assimilation by 10%.
Therefore,
notable variations are observed when applying the nutrient assimilation principle to the method and taking different NE ratios when performing the calculations, MCI increases value when the assimilation of nutrients
increases.
Conclusions
Improving digestibility, nutrient excretion is minimized, increasing the circularity associated to the feeding systems. Moreover, digestibility and sustainability are linked under the circularity perspective as nutrients are used in a more efficient way, facilitating the incorporation of the circular economy principles in the feed manufacturing process and farming operation.
Bibliography
Policy Recommendations For a More Circular Aquaculture: available in
http://ifishienci.eu/wp-content/uploads/2022/03/IfishcIENCi_Policydoc_Jan-2022Final.pdf
Acknowledgments
This work is part of the iFishIENCi project, funded by the EU H2020 research and innovation programme under Grant Agreement No 818036.