8. Economic considerations

8.1. Raw material quality

8.2. Pump water recovery

8.3. Blood water recovery

8.4. Stickwater recovery

We have now reviewed the process. We have isolated four areas of the process for consideration; raw material quality, pump water, blood water and stickwater where it might be possible to recover additional yield. Let's now look at the potential significance of the losses from these different areas.

The next stage in the process where there is a significant yield loss and therefore pollution of the surrounding bays and harbors is discharge of the pump water. With an average 5 year catch of 8.4 million metric tons of fish, the possibility exists that at a ratio of 2:1 water to fish, 16.8 million cubic meters of pump water is discharged into the Peruvian harbors in the average year. Based on the experience at the Pisco plants, and using our assumptions from Figure 11 we can calculate how much product is being lost and what the value of that product might be, based on average data. In Figure 42 we have broken down the Peruvian catch by port and have given the 5 year average catch for each of the ports. We then calculated how much fishmeal is being discharged in the pumpwater both before and after screening at each location. The difference between the two figures is how much additional revenue can be generated if 1 mm screens were installed in each factory. The average 50 ton/hour plant will generate 200,000 cubic meters of pumpwater per year with an estimated 11,322 metric tons of fish meal in it. The 1 mm screen will recover 4,440 metric tons of fishmeal worth $1.7 million in the average year. Screening through a 1 mm screen would be considered primary treatment. There are many types of screens available on the market today. One such device is the rotating hydro sieve which rotates opposite to the liquid flow that is introduced at a tangential angle creating a higher shear velocity. The milliscreen separates small suspended particles from the water and has been successfully used in many applications including the fishmeal industry. These screens can be obtained with openings as small as 0.25 mm.

The next source of yield loss and therefore pollution of the surrounding bays and harbors is discharged of the blood water. Blood water forms when the fish are stored in the raw holding bins. Pressure of the fish releases the liquid which contains oil and proteins. Based on our assumptions and the data published in the literature for other species, we have asumed that 20 kg of solids/ton of fish are lost per day and that the catch is all processed within one day. In Figure 43 we have calculated the losses from bloodwater for each location. While not as substantial as the losses from the pumpwater, the yield loss from discharging the bloodwater is still very significant. Again, for our average 50 ton/hour plant, the losses can be as large as 1110 tons of fishmeal worth an average of US$352,980 in a season.

In the USA and many of the other countries where fishmeal is produced, when the environmental regulations were being developed, the government first looked at what would be considered the best practical technology available to the industry. Best practical technology included the requirement for a stickwater plant or access to a stickwater plant. Fish contain about 80% liquid which consists of water plus oil. As the oil content of the fish increases, the water decreases and vice versa. Based on the material balance that was previously shown, stickwater represents about 60% of the weight of the fish that are unloaded and will contain about 8% solids. For plants that do not currently recover the stickwater, the losses in yield are enormous. Again, using our typical 50 ton/hour plant, about 30 tons of stickwater will be generated per hour. In a season, 60,000 tons of stickwater will be lost and at 8% solids, this works out to 5328 tons of fishmeal worth US$1.69 million. It also represents about 27% of the fishmeal that could be produced from the fish. In Figure 44 we made the assumption that 25% of the Peruvian plants do not have stickwater plants and then calculated the losses in fishmeal value for each of the ports.