Case study in Fish Processing

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1. Case study or built example

Case study

2. Industry Sector

Fish industry

3. Process description

Cleaner production assessment was carried out in a polish herring filleting plant. The company generally processes herring and cod and in total 4.000 tones of raw herring per year. Products of the different processes are frozen or marinated fillets. The production takes place in two mechanical filleting lines and one hand filleting line and the solid waste is treated in a fish meal plant owned by the company.

Figure 1: Process flow chart of the operation

4. Planning and organisation

The organic load in the wastewater was too high and neighbours complained about odours and effluent from the plant. Therefore the managing director decided to commit the company to a project which aim is to reduce the emissions to the environment. A team consisting of the managing director, a technical engineer and a supervisor was formed and furthermore consultants were pledged to assist with the project. It was decided by the project team to focus on the filleting line.

Overall aim:

  • To upgrade production while finding a compromise with local and central authorities
  • To address complaints of residents nearby


  • To increase yield
  • To decrease pollution load in effluent
  • To reduce odour
  • To improve work improvement


  • To increase yield by 3%
  • To reduce water consumption and wastewater volumes by 50%
  • To receive no complaints

5. Pre-assessment

Although the company processes herring and cod the project involved just the herring processing line.

A site inspection revealed following problems:

  • excessive waste on the floor caused by poor housekeeping
  • running hoses
  • poor hygiene
  • insufficient monitoring of yields
  • poor maintenance of equipment
  • a very damp, cold work environment: waste making the floors wet and slippery
  • a general impression of untidiness

After the inspection the team decided to focus on the herring filleting department because it generates a large quantity of wastewater with a high level of organic matter and it causes economic losses. Furthermore it was noted that the yield is 3-5% lower than optimum levels. It was also decided to find a way to improve hygiene, waste treatment and quality in the department in general.

6. Assessment

The first step was to make a sketch of the plant which depicted the water and wastewater reticulation system. Then water meters were installed which measured the following parameters of each key process:

  • water consumption
  • organic load (COD) and suspended solids content of the wastewater
  • energy consumption and
  • product yields

With the collected data various strategies of Cleaner Production were developed for every problem and process and were listed in a table.

After undertaking the strategies in terms of their technical and economical potential the team selected several options for implementation:

  • introduction of new process systems to improve the product yield
  • dry collection of offal
  • water saving opportunities
  • production of silage from offal

7. Implementation and Continuation

Then an implementation plan was drawn up.

Yield improvements:

  • A system for grading fish was introduced. An installed belt grader removes the fish which is too small or too big. This measure enabled the filleting machine to produce fish fillets of uniform size.
  • A production control system was installed and staff and the managers underwent training.
  • Equipment monitoring procedures were put in place which included the sharpening and changing of knives at each shift.
  • Product yield monitoring procedures were also introduced for each filleting line. Machines are adjusted based on the feedback from the monitoring results.

Dry collection of offal:

  • Small chutes guide offal and water to the filtration belt with 1 mm mesh size so that water and waste can be separated. The separated water flows to floor drains and is transprted to a microfiltration belt with smaller mesh size.
  • The separated solid waste is transported to the silage plant.
  • Wasterwater which contains offal from the floor is transported by gravity to the main filtrating for screening. Then the offal is added to main offal stream and is also used for the silage production.

Water saving activities:

  • Installed water meters record consumption.
  • Trigger nozzles were added to all cleaning hoses.
  • Solenoid valves on all filleting machines assure now that water is shut off during shut down periods.
  • Operators are made aware of water consumption.

Production of silage:

  • Offal is not sent to the fish meal plant any more, now it is used for silage production. The procedure consumes less energy and is used as fodder.

8. Results

After more than 6 months of production following points were noted:

  • Increased product yield (5-7%)
  • Less water consumption (20 m3/h instead of 32 m3/h), it results in total reduction of 37%.
  • Volume of generated effluent also decreased by similar amount.
  • Organic load in wastewater is reduced by 41-88%.

Silage is sold and represents an additional profit for the company. Furthermore its production does not generate any pollution and as consequence the fish meal plant has been closed.

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