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Meltwater flows from trucks transporting fresh fish. It is dangerous for traffic – and unnecessary
Researchers have the solution to the problem of runoff.
“The critical factor is that the fish are sufficiently chilled to a core temperature lower than 1°C before they are packed in crates filled with ice,” research scientist Bjørn Tore Rotabakk at Nofima says.
Together with other researchers, they have found the ideal temperatures for all stages, from packaging to the delivery of fresh fish. This will reduce the amount of runoff during transport.
Rotabakk took on the assignment from the Norwegian Seafood Research Fund, together with Christian Petrich from Sintef Narvik and Jørgen Lerfall from the Norwegian University of Science and Technology.
Model for calculating runoff
The researchers have produced a website with a model that will help the seafood industry calculate the volume of runoff that is produced based on the temperature of the packaged fish.
There are large variations in fish temperature control between the various industry players. The main challenge with runoff probably lies with the producers, where the fish are generally not cooled properly, according to Rotabakk.
Most of the fresh fish transported by trucks in Norway are transported in polystyrene crates chilled with ice. Insufficient cooling of fresh fish before packing and icing causes a significant amount of ice to melt during transport.
“If the temperature in the fish is 3 degrees, it produces almost 650 litres of runoff. If the temperature in the freight room is also set to 3 degrees, then you get a total of 740 litres during the first 48 hours of the fish being in transport,” Rotabakk says.
Slippery roads and foul odours
The meltwater is allowed to drain off the trucks through drainage holes and onto Norwegian roads.
Seafood companies and the Norwegian Truck Owners Federation estimate that a single truck can release up to 3,600 litres during a 36-hour transport.
Road authorities believe this can lead to slippery roads (both in the summer and winter), soiled ferries and foul odours. It can also create other traffic safety issues.
According to the Norwegian Broadcasting Corporation NRK, the Norwegian Public Roads Administration and the police have considered reporting fish farming companies for complicity in breaching the law.
Significant differences in temperature control of fish
The vast majority of participants in the study reported a target temperature of 1–3°C for fish packed with ice. The researchers conclude that this will result in ice melting and runoff during storage and transport.
Fast and effective cooling would be in the interests of the producers, distributors and consumers alike, as it reduces both the enzymatic and bacteriological activity, and thus provides better quality and extended shelf life of the fish.
“If you are unable to cool the fish well enough, for example during transport in the summertime, you can either compensate by postponing the shipment, or by using watertight crates,” Rotabakk says.
Several methods can solve the runoff problem
Several attempts have been made to stop the runoff problem, but no one has succeeded in eliminating it so far.
The researchers summarise the status quo in their scientific report Reduction of runoff meltwater from fish transport:
- Watertight crates seem to be a feasible alternative that can be implemented quickly as long as the fish is sufficiently chilled. Watertight crates must either be designed to collect the runoff meltwater without the water coming in contact with the fish, or an absorbent layer must be used that is capable of absorbing the runoff. Both solutions will be more expensive compared to the current solution, where the meltwater is drained away through drainage holes in the crates.
- Another option is to fit collection tanks underneath the trucks to collect the runoff meltwater. There are certain capacity issues with this option, as the tanks currently available only hold approximately 250 litres. It will also take time before tanks can be installed on all semi-trailers transporting fish in Norway.
- Another option is alternative refrigerants that do not produce runoff meltwater, such as CO2 snow and gel-ice. CO2 snow is costly and can involve HSE concerns. Gel-ice is also more expensive than ice and creates waste management problems for the customer.
Rotabakk et al. Reduksjon av smeltevann fra fisketransport (Reduction of runoff meltwater from fish transport), Nofima, 2023.
- The most important measure to reduce runoff from trucks transporting fish is to ensure that the fish is sufficiently chilled – i.e. to below 1°C – before it is loaded onto trucks for transport.
- Measures such as watertight crates and collection systems are feasible, but no systems currently exist that present a quick solution to the problem.
- A combination of improved chilling practices and watertight crates or collection systems could be a good option.
- A model has been created where you can calculate the volume of runoff meltwater produced based on the temperature of the fish as it enters the crate and the ambient temperature of the crate. The model was launched during the webinar on 18 April.
About the project
- Norway is a major seafood exporter, with exports reaching 1.7 million tonnes of wild-caught fish and 1.4 million tonnes of farmed fish in 2021. Of this, 1.1 million tonnes of the salmon was exported fresh, while 111,000 tonnes of wild-caught fish were sold fresh (Norwegian Seafood Council).
- The project was funded with 2.5 million NOK (roughly 237,000 USD) by the Norwegian Seafood Research Fund in the period June 2022 to March 2023.
- The project was led by scientists from Nofima, SINTEF Narvik and NTNU.
- The reference group consisted of representatives from Norfra AS, Nordlaks produkter AS, Grieg Seafood Finnmark AS, the Norwegian Truck Owners Association, Lerøy Norway Seafood AS and The Norwegian Seafood Federation
(Sources: The Norwegian Seafood Council, Statistics Norway and Nofima)
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