The Hout Bay Fishmeal Factory
The Hout Bay Fishmeal Factory
The fishmeal production process comprises three basic phases, namely indirect steam cooking, pressing of the cooked fish matter, and indirect drying. Evaporation units are used to concentrate the exuded cooked liquid (fish water); the concentrate is then added back to the fishmeal process before final drying. In summary, the process is a reduction of raw fish into fishmeal and fish oil, both of which are critical ingredients used in the specialised animal and aqua feed industry. At every stage, controls are in place to minimise unsavoury by-product and to ensure the quality of the ultimate product.
of The Hout Bay Fishmeal Factory
Catching and transporting raw material
The South African stocks of sardine, anchovy, round herring, and horse mackerel are highly mobile migratory fish that occur in South African waters from the Orange River on the west coast to approximately Port Alfred on the east coast. Wooden and steel vessels use a purse seine net to catch the fish in the upper layers of the sea, and shoal sizes can reach 200 tons per catch. The raw material is stored in the hold of the vessels and transported as fast as possible to the fishmeal plant.
Offloading and storage
Raw material is pumped from the vessel to the storage pits where fish water is drained from the batch before weighing. The fish pits are completely enclosed and have refrigerated circulating cold air in order to maintain good quality and minimise autolytic deterioration.
The raw material is conveyed into the continuous steam jacketed cookers where the raw fish is cooked, causing the liberation of the fish solids, oil and water. The plant’s cooker enables optimal temperature transfer and residence time for the fish.
Odour Suppression Plant
While the plant employs various odour suppression technologies to target and minimise odour, the plant has a characteristic fishmeal-processing smell. This is especially noticeable during periods of overcast and low ambient temperate, during periods with wind direction towards residential areas and during periods of windless conditions.
The smell comes mainly from the driers, where hot air passes over the cooked fish matter and in the process emits odorous vapours that are entrained in the air stream. The indirect drying process used at the plant has no air in direct contact with the fishmeal and the vapour removed from the cooked fish can be condensed because of smaller volumes of air.
The fishmeal factory collects all production emissions from cookers, conveyors, driers and other processing equipment and channels it though a high-capacity seawater scrubber. This assists in condensing the odourous vapour and all non-condensables are then channelled to a balancing tank which divides the gases either in a two-phase chemical scrubbing system or into four boilers for gas combustion. An oxidising agent is used for chemical scrubbing in order to react and minimise the odourous compounds.
Other elements of the odour suppression system include enclosed and refrigerated fish holding tanks at fish intake phase as well as bag filters in the bagging phase.
While the plant employs all the above technology to target and minimise odour, it cannot completely eliminate the smell of fishmeal processing. The factory’s intermittent operation schedules, which depend on fish availability as well as weather conditions during production, will produce the characteristic fish-processing odour. This may give a misleading impression of inefficiency at the plant and this website is part of our commitment to being open about the process.
The output from the cooker is then transported to a series of decanters which aid with the separation of the solids from the liquids.
The liquid is then pumped to centrifugal separators, producing stick water which is pumped into a holding tank for processing and oil which is polished and stored in tanks. The stick water contains fine solids which are concentrated in a Waste Heat Evaporator and this concentrate is then added to the solid phase in the driers.
Solids from the decanters are conveyed to indirect steam driers where concentrated process water is added to produce a mixture with a moisture content of 35%. Meal exiting the dryer is at a moisture content of less than 10%.
The bagging process has filters and cyclones that remove dust and recycle the fines back into the storage bags to reduce wastage. The final product is bagged into 50kg and/or bulk bags depending on customer demand.
Fishmeal – The final product is stored in warehouses pending despatch to customers.
Fish oil – The final product is loaded in bulk tankers and containers.
Boiler steam generation
The plant uses four John Thompson Oil Fired Boilers with a steam capacity of 14000 kg/hr for two boilers, 16000 kg/hr for the remaining two.
The water vapour from the two indirect driers is passed through a waste heat evaporator to re-use the heat, the remaining vapour is condensed in scrubbers and the non-condensables are ducted to a mixing tank from which the boilers draw air to incinerate the odorous vapour. The air from the plant is also scrubbed and fed into the mixing tank. The surplus air not burnt in the boilers is treated in a chemical scrubber.
At the Hout Bay Fishmeal Factory, sewage water effluent is pumped into the municipal sewage system.
No water effluent is discharged into the sea. The fishmeal production does not produce any production effluent. However all wash water which is produced during cleaning is pumped to the City of Cape Town’s sewage plant in Hout Bay. The factory samples the water effluent monthly and sends it to an independent laboratory for analysis. The plant utilises seawater in the scrubbers for cooling purposes and, if it does not come into contact with any plant liquids, is returned to the sea. This too is periodically sampled and then analysed by independent laboratories.
The Hout Bay Fishmeal Factory provides employment to 91 permanent shore-based staff and supports in excess of 120 seagoing employees.
Emissions from production processes at the Hout Bay Fishmeal Factory are associated with an unpleasant odour, the impact of which the plant is continuing to address and reduce.
Following a survey conducted in 1995-96, the CSIR produced a report on the impact of the factory – An Assessment of Community Exposure and Potential Health Effects of Emissions from the SA Sea Products in Hout Bay. The results of this survey confirmed that the processing of fishmeal and its associated activities do not constitute an environmental health risk.
A 2011 report of the St Helena Bay operations, based on independent studies and conducted on behalf of the Department of Environmental Affairs, also concluded that emissions at low levels pose no significant impact on human health. During recent and previous measurements of the exit gas from the odour abate system it was determined that the emission levels were within an acceptable range.
The plant operates under an environmental management plan (EMP), whereby fish volume restrictions are strictly enforced.
The Hout Bay Fishmeal Factory has undergone a thorough improvement process in the past two decades which has significantly reduced its odorous emissions.
Scientific analysis on raw material caught is performed daily and compiled into status reports. The data collected is used to monitor catches, abundance, distribution and biology and associated environmental information.
Some of the control measures included in this plan are the following
Odour complaints register
Representative analysis of all incoming fish is sent to independent and approved laboratories for TVBN analysis. This is an indication of fish freshness and is dependant on both time and temperature. Analysis results are reported to the licensing authority. Processing of fish must be undertaken within 24 hours after fish was caught
Processing of old or decomposed fish is prohibited
The plant reduces the intake of fish during unfavourable weather conditions
Proper maintenance systems are in place in the processing plant
Systems include preventative maintenance programmes
Management olfactory surveys are conducted on a daily basis (and when there are complaints) at key locations in the area surrounding the plant