World Aquaculture 37 • Stabilization with calcium dioxide and further sending to a rubbish dump: It requires having adequate facilities nearby plus a licensed manager to manage the wastes. No profit can be made out of this practice and it implies a high management cost. Heads, guts and bones. Heads, guts and bones are considered Category 3 wastes of animal origin and can be used for the production of pet food, biogas, compost, etc. in accordance with Article 33 of CE1774/2002. Twenty percent by weight of the processed degutted fish goes as waste and 50 percent of the processed filleted fish ends up as waste. This type of waste is produced through the whole year, with no specific production peaks. The current management alternatives for these wastes are the same as for dead fish (ensilage, burial in landfill, burial in controlled areas, compost producing) or other economically interesting alternatives such as: • Fish meal production. This requires refrigeration or freezing of guts. Proper equipment is needed. Currently, no profit can be obtained from this product. If the fish farm has the ability to send the guts to a fish meal factory and the distance is not too great, the factory could pay something. Cattleman would pick up the guts for free. No further profit can be made out of this option. • Mink feeding. This requires refrigeration or freezing of the guts. • Agrarian implementation. There is no cost nor profit, but periodic analysis of wastes and soils must be obtained where the wastes are thrown. The management of sludge, ensilage and fats originating in the water treatment plant were also studied. Proposed Solutions When the waste solids were identified and quantified, the expert team from AZTI-Tecnalia proposed on one hand, opportunities to minimize the generation of the wastes, and, when they are produced, the most suitable management for each, according to their characteristics and the quantities. Minimization opportunities. The generation of wastes has been found to occur principally in areas where minimization techniques apply: • Processing area: The use of appropriate cutting tools is essential, because it helps to improve the production yield. Another important improvement is the use of watertight or waterproof containers, thus avoiding contamination with dirty water. Installation of filters in sinks helps minimize the amount of solids in suspension in the wastewater. The dry recovery of solid wastes minimizes the use of water for floor washing and improves the quality of liquid wastes. • Degutting area: proper maintenance of the gutting machine and personnel training to get full efficiency in the degutting activity to improve productivity and reduce wastes. If trays are installed below the filleting machine, the wastes can be easily gathered, instead of falling directly on the floor. • Packaging: dealing with suppliers to negotiate the pickup of packaging materials and increase the use of large bags. • Dead-fish: to avoid fish death it is important to optimize the hydraulics of the pools. Another measure is to retain the solid wastes before pumping the water to other pools and to avoid overloading the pools with fish. • Feed: the optimization of the feeding method is a key factor to reduce feed cost (Cho 2006) and to minimize the generation of sludge in the pools. The best alternative is to fit the farm with facilities to reduce losses by feed handling. Exploitation Opportunities To make profitable use of the generated wastes, it was necessary to take into account the legal requirements. Some of the wastes were considered Category 2 according to the European Union legislation (CE 1774/2002), the volume of the produced wastes and their organic nature. The most problematic wastes to manage are fresh guts and the killed fish that are not marketable, the ensilaged products, the fats, the sludge from the pools and the dead fish. The alternatives of waste management applications were studied from the technical and legal points of view. The potential users of the wastes generated on the farms have been identified in the vicinity of the farms in an attempt to minimize the transportation impact and cost. According to the above-mentioned criteria, the uses of the different wastes are as follows:
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