70 September 2009 (Continued from page 38) Freshwater Fish Farms Table 1. Accepted maximum values for heavy metals in sludge PARAMETERS LIMIT VALUES Ground with pH < 7 Ground with pH > 7 Cadmium 20 40 Copper 1000 1750 Nickel 300 400 Lead 750 1200 Zinc 2500 4000 Mercury 16 25 Chromium 1000 1500 fish wastes, as well as dead fish. The European Union established a norm for the agricultural use of water treatment plant sludge by the 86/278/CEE directive. In this norm, the maximum limits for heavy metals in sludge to be used in agriculture were defined. These values are shown in Table 1. 5. Dead fish. According to law CE 1774/2002, dead fish were defined as Category 2 materials. Article 5, chapter 2.e states that dead fish are “animals or parts of animals not mentioned in article 4, that die without being sacrificed for human consumption, including those sacrificed to eradicate an epizootic illness.” In this law it is clearly stated that category 2 materials must be ensilaged or composted. But other alternatives are also allowed: • Incineration in an incineration plant. • Treatment in an authorized treatment plant to: 1. Eliminate the waste by incineration. 2. Use recuperated fats as fertilizers or other uses in oleochemical plants. • Treatment in authorized treatment plants to: 1. Use the proteins as fertilizers. 2. Transform in biogas plants or compost plants. 3. Eliminate in authorized waste dumps fulfilling the 1999/31/CE directive. There are some exceptions that allow, category 2 and 3 animal wastes, and always under authorities approval, incineration or “in situ” burying. The alternatives studied for the organic waste are summarized in the Table2. Conclusions Wastes basically originate from two sources: • Human activities: wastes produced by mishandling and inefficient procedures. • Equipment and facilities: lack of automation and obsoTable 2. Management opportunities for each waste type Possible Uses Fish meal Mink Compost Acid Biodiesel Animal Agrarian Glue, feeding ensilage feeding use varnish, paint Waste Type Fresh gut/ slaughtered fish * * * * Ensilage * * * * * Fats * * Sludge * * Dead fish * * * Possible uses of wastes lete equipment reduce the productive ratios and increase the generation of wastes. In each of the freshwater fish farms, the specific minimization opportunities have to be studied to identify the most suitable opportunities for each farm. As far as the valorization and management of the wastes is concerned, exploitation opportunities for freshwater fish farms are strongly limited by European Union legislation (CE 1774/2002), especially for dead fish, which is still a problem that needs to be solved. The remoteness of the fish farms and the inherent logistical costs for waste collection make it difficult to obtain any profit from the organic wastes. Apart from that, correct management of those wastes requires a major effort for the farms, basically because of the: • Need to separate wastes, which means the need to acquire specific storage devices for the different wastes. • Need to install refrigeration or freezing facilities to maintain fish waste in good condition until it is collected. • Long distances to be covered by truck to send the wastes to the authorized treatment plants. • Need to hire the services of a licensed waste managment company.
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