World Aquaculture 35 Application of several treatment techniques for solid wastes from freshwater fish farms Aintzane Esturo1, María Revuelta and Jaime Zufía Because of a shortage of some species by extractive fishing and the increasing worldwide demand for fish products, aquaculture seems to be a reasonable alternative to satisfy the demand. Aquaculture is an expanding sector in terms of increasing production tonnage and in the number of new cultivated species. The consumer demand for fish products has increased because it is known that they are healthy sources of protein and contain beneficial polyunsaturated fatty acids. But the modern life style does not leave much time for food preparation and the consumer demands products that are easy to buy and to cook. In the case of fish products, the demand for degutted and filleted fish is increasing dramatically. This presentation of the product produces increased waste at the production plants, creating environmental and economic problems, not to mention the difficulties in complying with environmental regulations (SFIA 1999). Aware of this situation, the Spanish Ministry of Agriculture, Fisheries and Food, decided to finance a project to help the development of the Spanish freshwater fish farming sector. The project was carried out by researchers of AZTITecnalia. The proposed work had two parts. The first one was to study the solid waste problem and the second was the application of minimization techniques on 10 rainbow trout farms in Spain. The location of the farms is shown in Figure 1. The project was financed fully by the Ministry. Goals and Methodology The main goal of the project was to establish the best alternatives to minimize and manage the solid wastes of the participating freshwater fish farms, with the partial goals of: • Obtaining a sector diagnosis of the environmental problems, • Evaluating the alternatives for minimization, recycling and final treatment of wastes for each of the participating farms, and • Identification of the feasible valorization possibilities for the sub-products and wastes, from the technical and economical point of view. The methodology used in this project involved: • Completion of waste characterization of the voluntary participating fish farms and conducting an environmental diagnosis, • Identification of the main requirements for the wastes, from the legal point of view, taking into account the European, Spanish and local legislation, and from the technical point of view, with a state-of-the-art technology review and identification of potential users (Henningsson 2004), and • Proposing a personalized action plan, considering the data obtained in the previous steps, such as the: 1. Suitability of the analyzed wastes for use as byproducts, 2. Economic and technological study of the waste minimization alternatives, 3. Identification and evaluation of valorization alternatives. 4. Definition of the process and logistics to make good use of the by-products, and 5. Disseminating the results. To carry out the waste characterization, a questionnaire was sent to the participanting farms asking for specific data about consumption and generated wastes (SEPA 2005). All the facilities were visited by the expert. In those visits, the technology used and the waste generation points were assessed. A confidentiality document was signed to ensure that the data given by the plant could not be used for purposes other than the application of the minimization techniques Fig. 1. Location of participant fresh water fish farms in Spain.
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