CIBELESα: circular bio-economy to lead an enhanced strategy for sustainable αquaculture

CiBELESα addresses the improvement of existing freshwater aquaculture systems in Germany and Colombia by incorporating microalgae cultures as a technological option for nutrients recovery from fish farms effluents. It encompasses novel processes for obtaining feed and high-value ingredients from harvested algal biomass and a water reuse strategy. This concept is thought to be tested under real conditions in both contexts by means pilot units. The consequences of increased circularity (materials/energy) will be studied by applying life cycle assessment (LCA) and related/complementary methods. The influence of different economic-environmental regulatory frames on this approach is a core topic to be elucidated. Specific issues in the light of the each study case are depicted hereafter:
Study case #1 (Colombia). It deals with artisan aquaculture developed by small fish farmers’ cooperatives in the interlinked wetlands of the Magdalena’s river basin at the Zapatosa’s swamp area, an ecosystem “of special value for species conservation”. Commercial purines are usual feed for fish (Oreochromis sp.) and the main cost. Feeding surplus and metabolic residues produce rich-nutrient
effluents directly discharged to the ecosystem threatening its sustainability. CiBELESα would stimulate feed from harvested microalgae, long-term protection for the ecosystem and diversified income.
Moreover, an “energy farm” underpinned with solar cells and an anaerobic digester fed with process side-streams would guarantee a self-sufficient/renewable energy supply.
Study case #2 (Germany). The “twin” scenario is provided by Salmonid farms located in BadenWürttemberg, which represents 56.2% of German aquaculture1. It uses raceway systems and ponds, requiring significant improvements in effluent discharges. Current feed (fish meal/oil, soya proteins) mean 30-70% of operational costs 2 and is linked to unsustainable production practices. Therefore, this project aims a platform for technology transfer and stimulating sustainable domestic value chains, especially for rural production facilities through the “proof of concept” of aquaculture coupled to microalgae production under constraints enforced by the EU’s regulations in matter of effluents recyclability and nutrients management, as well the fine tuning of some technologies at laboratory level (e.g. cells disruption) for enhanced recovery of proteins and high-value ingredients from algal biomass for feed and further applications.
This project engages several driving principles of the present call, notably the production of microorganisms for primary production, innovative biotechnology for bio-based products and the analysis of limitations/possibilities of bioeconomy in clearly differentiated settings.

Aquaculture is the fastest growing branch of food industry (+527%, 1990-2018), responding to the protein demand of the rapidly growing world population. Among alternative sources of feed for fish, microalgae possibly have the biggest potential due to their high content of proteins, oils and high-value substances of rapid metabolism, as well astheir genetic diversity and adaptability. However, only small quantities of microalgae products are marketed, because of costs and restrictions. Indeed, very few microalgae derivatives have been approved forhuman consumption in Europe owing to the NovelFood Regulation (EU 2015/2283), despite some strains accumulate protein levels of up to 70%.
Nevertheless, the feeding stuff sector seems a promising field for microalgae; for instance, the petfood and special feed sectors are interested in replacing synthetic carotenoids and vitamins and notsustainably produced oils by “greener” ingredients. Thus, the increasing demand for protein-richcompounds is unlocking opportunities for microalgae produced in systems with minor environmental impacts and contamination risks, which can be reached by using closed PBR developed in Germany. Integrated aquaculture-microalgae systems should boost ecoefficient models for domestic value chains in Germany and Colombia. Effluents management would focus on nutrients recovery and water
reuse for microalgae conversion to feed in two settings: PBRG and ORPC . In Germany, the aim is to secure/expand the added value of existing industrial, especially rural production facilities, also settling the use of renewable energy. The suitability of this circular bioeconomy concept will be relied on LCA
and feasibility studies comparing both case studies. Further co-benefits in Colombia are related to enhanced protection of its unique hydric ecosystems by improving aquaculture practices and diversifying their income through microalgae-based outputs.

Aquaculture effluents can be used as a source of nutrients for growing microalgae to produce a safer and “greener” feed for fish1-4 , because it would avoid widespread practices, such as feeding fish with manure or pellets of animal/vegetal protein. The first a tolerated practice in some tropical aquaculture cases that holds a latent risk for parasitic diseases transmission through the food chain5 ; the second an important input of “imported nutrients” to the system boundaries, which are lastly sent back to the water cycle promoting eutrophication events6-10 . A vision clearly complementary with an earlier approach presenting microalgae processes as dual-purpose systems providing simultaneous wastewater treatment and flexible feedstock for biorefining, namely, a sort of microalgae system free of freshwater footprint, their more sensitive criticism11-13
.
Nutrients (P, N) recovery from swine and human effluents by means microalgae-based posttreatments is a major challenge in this field; in fact, microalgae biomass grown in wastewater is almost exclusively devoted to biofuels production, since food, feed and derivatives for direct/indirect human consumption are restricted, particularly in the strict EU’s regulatory context14-16, despite their upper nutritional properties regarding to commercial proteins for fish and livestock rearing13, 17 . Meanwhile algae, like Spirulina sp. and Chlorella sp., among other strains that thrive in diverse waste streams
provide an attractive pathway for coupling aquaculture to microalgae cultures for self-supply of feed or dietary supplements for fish, shaping a close-loop of materials2, 5, 18, 19
. Thus, it is expected a better economic-environmental integration, if selected microalgae species overcome typical drawbacks due to excessively rich-nutrients mediums (e.g. purines, sewage), such as toxic effects by nitrogen
accumulation16, 20 or insufficient phosphorus uptake8 . Effectively, aquaculture effluents seem more adequate for a balanced operation and easier nutrients control for microalgae growth2, 3
On the other hand, specific concerns about biological safety of microalgae-based products cultivated in wastewaters, as well the recirculation or reuse of these effluents, are addressed by incorporating inside the process schema some chemically non-intrusive pre-treatments, specifically UV radiation, which has proved to be effective reducing microbial densities, inactivating virus and fostering growth rates of Chlorella and other strains3, 21, 22
. Likewise, ecological disinfection with solar collectors would allow a safe end-disposal or irrigation use of the end-effluents of microalgae-based process23
.
Moreover, downstream strategies for more complex process involving recovery of high-value ingredients are being taken into consideration. For instance, biomass slurries and wet biomasses left over from cells disruption and lipids/protein extraction processes are suitable for delivering valuable biogas and organic fertilizers by means anaerobic digestion24
.
Nonetheless, the favorable environmental response of aquaculture coupled to a microalgae production system would be not granted, without applying well-established methods for this purpose.
From the pioneer application of the LCA methodology to appraise aquaculture as ecological remediation system25, its application have been extended to study microalgae processes13, 26, 27 ,compare fish farming systems and elucidate the consequences of their intensification in Europe13, 28, 29
and abroad4, 9.
Nowadays, LCA combined with physical-flows accounting methods(e.g. emergy, exergy) are giving rise to new routes for estimating “renewability” or “circularity” indexes and appraise changes in the quality of some ecosystem services affected by the economy system30, 31. In fact, it presents a more complete approach to tackle sustainability issues in a wider sense, with relatively recent and relevant applications for agricultural and aquaculture system.

The aim of CIBELESα is to validate a technical concept of freshwater aquaculture coupled to a microalgae cultivation-processing system for producing feed and high-value ingredients, with improved circularity of nutrients and water, ruling a sustainable bioeconomy model for communities settled within delicate hydric ecosystems.

O1: To describe and evaluate the state-of-the-art of freshwater aquaculture systems in Colombia and Germany regarding the technical implementation and their economic, environmental and normative suitability at affected sites, including socio-economic aspects within the local rural environment (WP1).
O2: To confirm the optimal operational conditions of the critical technologies enabling the effective and stable performance of the integrated process; e.g., to test Phosphorus removal (>80%) from aquaculture effluents by an enzymatic approach and pretreatment by using UV radiation to prevent biological contamination. It includes the validation of microalgae production in pilot PBRs and ORPs. The overall concept will run on full renewable energy supply
relied on an “energy farm” (WP2.1 to 2.5).
O3: To develop a feasible process to recover high-valuable nutrients from the microalgae biomass by confirming that disrupted microalgae biomass has increased bioavailability and evaluate its potential uses (e.g. fish feeding, other) (WP2.4).
O4: To assess the ecologic and economic advisability of the technological concept posed by CiBELESα on the basis of the comparative LCA methodology and determine potential regulatory burdens or market constrains, which influence differently the case studies (WP3).