Most of the fish wastes are utilized to produce fish meal in Sri Lanka. Peliyagoda fish market produces nearly three tons of fish waste per day and around only one ton of fish waste is used for producing fish meal.
by J.M.N.J. Jayathilake
Current situation in Sri Lanka
Sri Lanka produces about 530,000 MT of total fish catch annually from 500, 000 square kilometers of ocean area where there are exclusive fishing rights and nearly 2900 square kilometers of inland water bodies. We export less than 3% of the total catch while importing 100,000MT of fish varieties becoming a main fish and fishery products importer in South Asian region.
On the other hand, we generate considerable amount of fish waste either in solid form or liquid forms. FAO says that we lost tons of fish catch because of an array of undesirable characteristics such as extreme heterogeneity, small size, flavor, bony structure, unacceptable appearance, substantial fat content, threat of toxic substances plus mainly, due to improper handling and during the fish processing operations. For an instance, nearly one ton of fish is discarded daily without getting any use from Peliyagoda fish market which is the largest whole sale market in the country. Other than that, in fin fish processing, two third of the whole weight is discarded in the form of gut and frames. Processing of prawns generate waste about 25% of the total weight depending on the final product. This has two major consequences; environmental and economic.
Though this is not a famous topic among the public, awareness in possibilities of conversion fish waste into useful products is important towards a sustainable future. There are some projects that fish meal and manure are manufactured using fish waste in the country but still, the local requirements aren’t fulfilled by the production output.
Further, different byproducts and value added products can be developed including food supplements, pet feeds, pharmaceuticals (chitin, liver oil, calcium, vitamins, minerals, peptides), cosmetics (collagen) and other products such as fish leather. Currently, there are more innovative products in the experimental level which need to be introduced and incorporated with the industry.
Moving to waste management to resource management.
Most of the fish wastes are utilized to produce fish meal in Sri Lanka. Peliyagoda fish market produces nearly three tons of fish waste per day and around only one ton of fish waste is used for producing fish meal. Later, the government established and maintaining Ekala fish feed factory in order to produce nutritive and cost effective fish feeds for local industries. It has been sponsored by FAO and technical assistance was given by NARA. Recently, a high capacity technological facility was established to satisfy the local requirement of fish feed and remaining is aimed to be exported.
Sri Lanka has fish processing, shrimp processing and tuna processing plants which are ideal opportunities to extract pathogen free good condition fish waste. They also could be used as a pet feed ingredient, as it represents a valuable source of high‐quality protein and energy. Moreover, Tuna fish heads have been observed as an excellent source of fish oil in the form of unsaturated fatty acids. The oil extract percentage is nearly 4%. Though this can be implemented in fish processing plants in Sri Lanka, still there is no any effective program or project to conduct this process. Specially, fish species like Sardinella longiceps (Yaksalayo) which have no market value also can be utilized to produce fish oil as they are rich in oil.
Fish silage is another potential product that can be produced by fish waste within the country. Fish silage is a liquid product resulting from the liquefaction of a whole fish or a part by a autolytic process carried out by enzymes already present in the fish and accelerated by an acid that induces the proper conditions for the enzymes to breakdown the tissues and limits the growth of spoilage bacteria. This operation is simple, economically feasible and no sophisticated equipment are required. Unfortunately, none of the fish processing plants in Sri Lanka is producing fish silage using offal. There is a previously established fish silage plant in fishery harbor, it exists without getting the maximum use.
Most of the fish markets expel their solid and liquid wastes with urban waste without treating. The extensive literature on biogas production using many animal materials have been tested, but not fish waste. It’s relatively a good option to implement near small scale fish markets and landing sites. In addition, produced biogas can be used directly in a burner to produce thermal energy, electrical or mechanical energy.
Chitin and chitosan are food additives that can be extracted from crustacean exoskeleton which contain 15–20% chitin by dry weight. Collagen extracted from hygienic fish waste, can be used to produce valuable ingredients in cosmetic industry which is an alternative to animal collagens. They can be utilized for supplementing the skin of land vertebrates as well as in foods and biomedical materials. Fertilizers and food packaging are also can be found among most prominent current uses of fish waste worldwide.
gelatin extracted from fish skin, calcium supplements from fish bones, flavoring agents from prawn heads are among other value added potential products which are still in the stage of research and development. Researchers have shown that a number of useful compounds can be isolated from fishing industry waste including enzymes, proteins and many secondary metabolites that have antimicrobial and antitumor and antioxidant capabilities.
In the Sri Lankan context, there is a gulf between science and technology, together with the research findings and the commercial reality. Along with, skilled people with innovative ideas are abundant but the opportunities for them are rare. However, it’s necessary to turn into methods that convert fishing industry waste into valuable products on the roads towards sustainable development. That will be a huge step forward from the waste management to the resource management.
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