Scientist calls for use of natural refrigerants in ice slurry systems on fishing vessels

May 19, 2023

Though ice slurry refrigeration systems offer many advantages for the fishing industry, there are few ice slurry systems installed on fishing vessels that use ammonia (R717) or CO₂ (R744) for ice slurry systems.

That was the assessment delivered by Kristina Widell, Senior Research Scientist at SINTEF Ocean, at the 10th International Institute of Refrigeration (IIR) conference, held in Ohrid, North Macedonia, April 27–29. She spoke on behalf of the CoolFish Project, funded by the Research Council of Norway, to provide a sustainable solution for chilling Norwegian seafood and reducing CO₂e emissions.

While the potential for development is evident, the current lack of market interest in natural refrigerant solutions in the fishing industry hinders its progress. “There is an urgent need to address refrigerant leakage and transition to natural refrigerants in onboard fishing vessels since the use of high-GWP refrigerants is hindering progress towards sustainability,” Widell said.

Efforts are needed to raise awareness and foster industry-wide collaboration “to unlock the full potential of ice slurry system in seafood preservation in the fishing industry,” she said.

The most efficient chilling rate

Widell believes that an ice slurry system provides “the most efficient chilling rate along with an option of cold thermal energy storage,” said Widell. Other ways of chilling fish onboard include ice storage and refrigerated seawater (RSW).

Ice slurry systems require a refrigeration system connected to an ice slurry generator, a storage tank for the produced slurry and possibly a mixing device to correct the water/ice ratio.

Ice slurry offers distinct advantages over flake ice in seafood chilling, said Widell. Comprised of small, microscopic ice crystals, slurry effectively fills the gaps between fish, facilitating enhanced heat flow and resulting in a high chilling rate.

Unlike water, slurry aims to harness the latent heat stored within the ice crystals. Control over latent heat can be achieved by producing slurry with a specific ice fraction or concentration. By capitalizing on these features, slurry ensures optimal heat transition and provides a more efficient and controlled environment for seafood preservation, said Widell.

Thus, ice slurry systems offer significant advantages in fish preservation, including rapid cooling, gentle handling, extended shelf life and improved product quality. The slurry-chilled fish exhibit better microbial conditions, enhanced water binding capacity, improved texture and increased freshness.

In addition, the pumpability of ice slurry ensures easy transportation and distribution, streamlining the chilling process.

“Studies conducted on various fish species, such as European hake, farmed turbot, perch, horse mackerel, salmon and cod, have consistently shown superior quality parameters when utilizing the slurry system,” said Widell.