38 September 2009 1. Fresh guts and nonmarketable slaughtered fish. Fish meal production. According to a previously study by AZTI-Tecnalia on freshwater fish farm wastes, some aquaculture plants in Spain were sending their wastes to fish meal plants and the tendency was increasing. This was the best alternative for heads, guts, and non-marketable killed fish. A list of fish meal factories in Spain was handed to the fish farmers so they could contact the nearest one. It was important to highlight that dead fish could not be used to produce fishmeal. Mink feeding. Mink farms were interested in receiving fish guts and fish suitable for, but not marketed for human consumption as long as they were in good condition. A good option was to freeze the byproduct in 500 to 1,000 kg packages and send it to the mink farms. Dead fish cannot be used for mink feeding. Compost. The wastes could be used to produce compost, even if they were considered Category 3 according to articles number 5 and 6 of the CE number 1774/2002. New Spanish law RD 824/2005 about fertilizers includes a list of biodegradable wastes to be used as fertilizers in which aquaculture wastes fit in sections 02.01and 02.02. The wastes have to be ground and undergo heat treatment at 80ºC for five minutes and obtain a local authority certificate assuring that the Fig. 2. Profile of fatty acids in ensilaged wastes. product has been exposed to adequate treatment and that it was inert. Acid ensilage. This is another alternative to manage guts and noncommercial fish in a simple way. It consists of accumulating the wastes in a silo together with acids. There was no need of refrigeration or freezing and the product could be collected every 2-4 months. The disadvantages of this option are that not many animal farms were interested in ensilaged fish wastes (they prefer fresh or frozen fish), the transport of liquid was not as easy as for solids, the price in the market was quite low and it required personnel to put the wastes into the silo everyday. 2. Ensilaged wastes. Samples taken from different silos were analyzed and it was observed that they had a high content of fats and oils. When the oils were analyzed it was observed that the oil profile corresponded to that of the fis, so it could be used for similar purposes as the fish oil: animal feeding, industrial applications and biodiesel generation. Oils obtained from ensilaged dead fish could not be used under any circumstance for animal feeding. Considering that 70 to 80 percent of the ensilaged material is water, it might be useful to install fat separators to facilitate the fat and oil extraction from the silos. The profile of the fats and oils are shown in Figure 2. Biodiesel production. Biodiesel producers use plant and animal oils and fats as raw materials (de Sena in press), but they have some problems with various animal fats but have shown an interest in using fish oils. Fish meal and fish oils for animal production. Because of the high amount and good quality of fish oil obtained from ensilaged wastes it may be possible to use it in animal production. It would be necessary to do further research and to install a centrifuge to eliminate the water. Some fish meal producers have already shown interest in this product as well. Direct animal feeding. A mink farm has shown interest in using fresh fish wastes to feed mink and also sees a potential role of using ensilaged wastes as feed. Further research needs to be done to study the second option. 3. Fish oil. Most of the oil is currently gathered in the water treatment plant but is generated in the trout cleaning area. Therefore, it would be worthwhile to install separating devices to gather the oil and treat it separately. This way, the byproduct could be managed as fish oil, and not as water treatment waste. The most important uses for the oil are industrial applications, such as the biodiesel, lubricants, leather production, or other applications for glue, varnish and paint production. Dobrzanski (2002) found that the fatty acid profile was very similar to the profile of salmonid fish oil, with high oleic, linoleic, linolenic, palmitic and eicosapentaenoic acid. Results of the analysis are as shown in Figure 3. 4. Sludge. The sludge is produced basically in the water treatment plant and the decantation pool. The sludge could be used to produce compost together with other Fig. 3. Fats in water treatment plant (Picture 15) (Continued on page 70)
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