Cleaner Production in Fish Processing
Fish industry is very widespread in terms of operation types, scales of production and outputs. Species of fish processed are cod, tuna, herring, mackerel, salmon, pollock and many others. 90% of worldwide fish production is accounted by marine fish, with the remainder being fresh water fish and fish produced by fish farming. Generally fish processing operations are located close to fishing areas. Some sectors like the salmon harvesting season are just seasonal.
The most important fish area is the northwest pacific region in term of caught volume and processed. China, Peru, Chile, Japan, USA, Russia and Indonesia are the top producing countries. These nations produce more than a half of worldwide fish production. Approximately 75% of worldwide production is used for human consumption. The remainder is used for processing fish oil and fish meal. Only 30% of fish produced for humans consumptions are marketed fresh. The big part is marketed in frozen form or in form of ready- to- eat-meals and other form of products.
The life cycle of fish products commences with the capture or growing of fish. Then the fish are processed to different products like fillet (fresh, frozen, marinated), canned fish, fish protein products like sumrimi, fish oil and fish meal. Fresh products are highly perishable and require a refrigerated storage because of preventing the microbiological spoilage. Highly processed products like canned fish have a longer shelf life and need less refrigeration than fresh products. The cycle ends with the consumption of products by human or animals and the disposal or recycling of the packaging
Figure 1: General flow diagram for fish processing
3. Environmental impacts
In fish industry generated waste is generally highly perishable and has to be refrigerated because if not it spoils rapidly. Flesh becomes soft and loose and lost pieces can find their way into effluent stream.
- Water consumption:
Like in other food industry sectors the high consumption of water is a problem in term of environmental pollution. Water is used for holding and transporting fish, cleaning equipment and working areas, washing raw materials and products, thawing, de-icing and for fluming offal and blood. In fish meal and oil production sea water is furthermore used for cooling and condensing air from evaporators and scrubbers. A lower rate of water is required for the centrifuges and steam production. Automated processing equipment has installed water sprays which flush the offal away.
Typical ranges of water consumption:
- ~5-10 m3 for filleting
- ~15 m3 for canning
- ~0.5 m3 for fish meal/oil production
- ~20 m3 seawater per ton of fish intake
- Effluent discharge:
A high rate of water becomes effluent. The effluent itself is influenced by the perishable nature of fish and fish products. Products losses also contribute to the waste loads which are often mixed accidentally with the effluent stream. Effluent of fish processing contains a high level of organic matter like oils, proteins or suspended solid, phosphates, nitrates, scraps of flesh and blood, soluble substances, detergents and cleaning agents. The main source of effluent are handling and storage of raw fish followed by processing, fluming of fish and products, defrosting and cleaning. In canning operations the effluent is generated from draining of cans after precooking and from spillages of sauces, brines and oil. In fish meal and oil production the major sources are the bloodwater from the storage and unloading, stickwater from the centrifuges and the condensate from the evaporators. The quality of the effluent depends on type of processed fish. Oily fish species like salmon and tuna cause more pollution loads because of their high oil content and because they are generally not gutted or cleaned on the fishing vessel. It also depends on the type of processing. For pickling of fish brine is used, therefore the wastewater will contain salts and acid. If the effluent is discharged into the water bodies without correct treatment the pollutants can cause oxygen depletion, pollution of beaches and shores and oil floats on the water which end up in the surrounding coast line.
- Energy consumption:
The rate of consumed energy depends on the age and the scale of the plant, of the range of products and the level of automation. Energy is required for operating machinery, producing ice, heating, cooling and drying. Processes which involve heating are particularly energy intensive; processes like filleting require less energy.
- 65- 87 kWh per ton of fish intake for filleting
- 150-190 kWh per ton of fish intake for canning
- 32 kWh per ton of fish intake for fish meal and oil
- + 32 litres of fuel oil
Because of the use of fossil oil resources energy consumption causes air pollution and produces greenhouse gas emissions which are linked to global warming. Therefore use of more environmentally benign resources is proposed.
Typical by- products are surimi and flaked fish. Hydrolysed fish wastes can be used for fish or pig meal or as fertiliser component. A well organized management of by products is very important because additional revenue can be generated and disposal costs can be lowered.
- Air emissions:
In the fish industry sector odour can be an important environmental issue. The major sources are storage and bad handled waste material. Odour is also generated during cooking and drying processes in fish meal production-
Refrigerant systems often use chlorofluorocarbons (CFCs). If they are released to the atmosphere they have a serious effect on the environment. Therefore the systems are often replaced by non- or reduced CFC- systems.
4. Cleaner Production opportunities
In general little use of hazardous substances is common in fish industry. Therefore following described Cleaner Production opportunities focus on reducing the consumption of resources, increasing yields and reducing the volume and organic load of effluent streams. Because of its delicate nature, slippery surfaces and size variations it is very difficult to automate the handling of fish and fillets. So generally the fish and fish products are directed in manual way through the processes. This means that the operator has an important rule in terms of plant performances.
- Water consumption:
Measures for water savings are very common in the food industry sector. Water is used for cleaning, for flushing offal and blood from equipment and areas and for fluming offal to floor drains and collection sumps. The first step for reducing water consumption is to make an analysis of water use pattern with water meters. The data should be discussed and weak points should be identified. An example for a “weak point” is running hoses which are not in use, because they cause a continual and unnecessary run of water. A solution can be automatic shut-off equipment. Then a fix minimum rate of water has to be specified to assure the hygiene standards and undisturbed process operations. A rational solution for the reuse of wastewater from fish thawing is its use for offal fluming or for initial cleaning.
Figure 2: Checklist of ideas for water savings
- Effluent discharge:
The objective of implementing CP is the reduction of pollutants in the effluent and effluent volume in general. The measures are closely linked to water consumption. Less consumption causes less effluent.
Figure 3: Checklist of ideas for reducing effluent loads
- Energy consumption:
Electricity is used to operate machinery, lighting, air compressor and cold storage. Thermal energy in form of steam and hot water is used for cooking, cleaning and sanitising. In this area often no capital investment is necessary and simple better housekeeping and optimisation of existing processes is enough to lower energy consumption. More savings can be made also by using improved and more energy-efficient equipment and heat recovery systems. Additional savings of plants demand for energy can be made by use of benign sources like naturals gas for generating thermal energy and renewable sources for generating electricity.
Figure 4: Checklist of energy saving ideas
One strategy for waste reduction is the recovery of marketable by-products. Good examples are surimi and flaked fish. Chitin and Chitosan are chemicals which are extracted from crab and shrimps shells and which produce polymers which are similar to cellulose. Chitosan is used for the production of animal meal products and in various medical applications. Hydrolysed fish wastes are applied as fish or pig meal or as fertiliser component. The collection and utilization of these by-products can only be realized by the presence of dry transportation of offal. Strategies for transport without water are for instance the installation of filtering conveyors or a vacuum system. For plants with many manual operations bins for collecting the offal can be provided.
Reference: Cleaner Production Assessment in Fish Processing; prepared by COWI Denmark for UNEP (United States Environment Programs) and Danish Environmental Protection Agency, 2000 Denmark
- case studies