Super-cooling of fish leaves a smaller environmental footprint
Dry ice has long been used as a cooling medium. It is well-known that dry ice becomes gaseous when it sublimes (evaporates from solid state). This, together with the degree of cooling, is the basis for the concept's commercial name: SuperGreen.
Stig Are Karlsen (left) and Thomas Juve emphasise SuperGreen's good environmental effects. "We've worked with super-cooling of fish since 1998, and are continuing to develop this product," they say. (Photo: Tom Riis)
"We've worked with super-cooling of fish since 1998, and are continuing to develop this product," says Stig Are Karlsen, head of market development at Yara Praxair.
Lowering the investment threshold
Today, one pallet of fish from a salmon facility on Sotra in Norway is bound for the USA, and another for Korea. These are time-consuming trips, with the fish being shipped to demonstrate to a customer that the technology really works. "The customer needs to see for itself that super-cooling is better than the traditional cooling method," says Karlsen.
Karlsen makes a distinction between water ice and dry ice. Today, water ice is the dominating method, but Karlsen and his department at Yara Praxair wish to change this. "We're working to improve our technology and lower the investment threshold," he says.
Yara Praxair's strategy is to focus on megatrends. "The world is facing a population explosion. If we are to eat healthily, on a sustainable basis, we need to make greater use of aquaculture," says Karlsen.
Production of farmed fish is increasing and expansion of the markets requires greater use of expensive and time-consuming transport. "We're talking about large volumes. Every 20 minutes a trailer crosses Norway's border," Karlsen says.
"Super-cooling has a really positive impact on quality, which is a competitive advantage," says Thomas Juve of Yara Praxair's market development department.
The combination of low temperatures during storage and transport, together with the surrounding high CO2 concentrations, inhibits all bacteriological growth while the product is super-cooled.
"For super-cooling of fish we use pre-dosed dry ice. The energy from the dry ice lowers the product's temperature to around -1.5ºC. Water ice would never be able to lower the product's temperature so much," says Juve.
The dry ice sublimes in the course of five to seven hours. The fish, either fillets or whole fish, will have become its own refrigerator, and will retain a guaranteed unbroken cooling chain for up to 80 hours. "This means that the production facility can control the product's quality right up to when it reaches the consumer, which is not possible with water ice," says Juve.
The sublimed dry ice in gaseous form is led out of the crate of fish, which is another important aspect of SuperGreen: the weight in the crate is equal to the weight of the fish, because the dry ice has gone.
"This means that the dry ice does not give any extra weight during road or air transport. Traditional cooling requires three to four kilos of dry ice per crate. This weight difference has a big impact on transport-related CO2 emissions. SuperGreen is ecofriendly," Juve emphasises, adding:
"It's also very expensive to transport many kilos of water by air."