Best practices for zero waste: Public deliverable report D4.1

The WP4 aims to develop more efficient systems to produce aquatic organisms, with minimal production of effluents and better use of resources. Several experiments were carried out in open ocean, semi-closed and closed IMTA systems. Trials for waste reduction have been focussing on the closed and semi-closed IMTA systems as nutrient in- and out flow can be followed to assess nutrient dynamic. In Brazil, the possibility of combining oysters and tilapias as filters of organic matter in an integrated culture with Pacific white shrimp in bioflocs was investigated. In this same system, the effect of introducing seaweeds to reduce of nitrogen and phosphorus concentrations in the water was also assessed. In South Africa, tests were carried out in a commercial abalone culture with the aim of increasing water recirculation to 75%, with the water being treated by macroalgae, which reduces nutrient concentrations and are used as food for abalones. In Ireland, integrated farming of fish, scallops, lobsters, urchins, oysters and macroalgae is being developed in open sea. In a similar environment condition, different species of macroalgae and native oysters are integrated in Scotland. In Brazil IMTA-lab the results observed in this period indicate that it is possible to control the nutrient concentrations with plants (seaweed) in the shrimp culture. Regarding the total suspended solids generated in shrimp culture in biofloc system, oysters were not as effective as
tilapias in removing particulate matter (bioflocs). Microorganisms present in the bioflocs and probiotics helped to keep the water quality, transforming toxic nitrogen compounds (ammonia and
nitrite) into less toxic ones (nitrate). In addition, microorganisms serve as food for shrimp and tilapia, improving the feed conversion rate. In South Africa IMTA-lab, during the abalone production process, so far, the integration with seaweed has provided a reduction in nutrient concentrations, external feed inputs and greater water recirculation (50% of the total volume), reducing considerably the emission of effluents to the environment. In addition to the benefits on water quality, seaweed serve as supplementary feed for the abalone, making the system less dependent on external supply. The project is still in progress and experiments are underway to further increase recirculation, further reducing energy consumption and effluent emissions.