Thinking inside the box

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Second-hand shipping containers have found all sorts of uses, from schools and theatres to pools and labs. Now, thanks to Finland’s Natural Resources Institute, we can add another: a prototype salmonid farm.

How does it work? “The unit includes both a fish tank and the necessary water recycling technology,” explains the foundation, which is also known by its Finnish acronym “Luke”.

The container-based modular solution enables scalable plug-and-play farm solutions. The core idea of the developed plant concept is “modularity”, and the utilisation of multi-functional technologies in water treatment.

Project leader Tapio Kiuru says the modular concept brings savings in design costs, component manufacturing and procurement costs, and plant set-up costs. Other benefits, he adds, include low water consumption, energy efficiency and a fast production cycle.

The fish farm, assembled from ready-made modules, also enables a rapid assembly and start of production. Production can be phased and it can be flexibly scaled. The foundation said: “The modular plant concept and the possibility of a simpler partial circulation of water instead of full recirculation also makes implementation of new technology easier.”

Kiuru adds: “Luke’s method can meet several of the current key challenges in circulating aquaculture, such as high investment costs and, for example, high feed and labour costs.

The key idea, he explains, is the use of multi-functional technologies in order to save investment and running costs. Other advantages include energy efficiency and low water consumption, as well as allowing a production strategy to ensure there are no “off-flavour” problems.

He says: “When it comes to shipping containers, we are not the first to bring them to aquaculture, but Luke’s new innovation makes the effective utilisation of shipping containers possible in aquaculture.”

A prototype of a fish container unit has been tested in Laukaa. How successful has it been so far? “We have grown six batches of rainbow trout so far in our pilot farm which has two 40-foot container units and one 20-foot container unit,” Kiuru explains.

“Results have been extremely good in all respects and there have been no off-flavour problems at all when we have used these systems in intensive partial re-use aquaculture system (PRAS) mode. The feed conversion ratio (FCR) has been below 1.0 in all six patches that have been produced so far.

“We were quite surprised to see below 1.0 FCRs even when the final size of the trout was 3.4kg. It might well be that the full production capacity has not been seen yet, as the best- performing group was actually the one that had highest final density (105kg/m3) that we have tested so far. In this case, final size of trout was 1.27kg and FCR was 0.83. Also other production parameters were quite impressive – specific growth rate (SGR) of 1.48 and mortality of 0.05%.

“Our full-scale experiments with trout sizes from 90g to over 3,000g have shown that over 100kg/m3 final densities are possible in these systems. Maximum feed load in our trials have been 1kg of feed per 1m3 tank water per day, so in theory maximum production capacity of one 40-foot unit could be over 20 tonnes per year, as water volume is about 50m3. However, it is not possible to use all tanks with full capacity all the time. Our results suggest that 10–12 tonnes per year is a realistic production capacity for one 40-foot container unit and production capacity of the farm depends on number of the units.”

Small is beautiful

Luke has applied for a patent for the developed technology and Business Finland Research has granted funding of €378,000 (£323,000) for a commercialisation project.

“We believe more reliable and cost-effective technology can attract producers not only from recirculating aquaculture system (RAS) sectors, but also from traditional sectors when sustainable intensification is sought after. We believe this technology fits especially well to small or medium-sized producers,” says Tapio.

He adds: “This is, in a way, a reversal of current trends in building larger and larger RAS farms, but our first results have shown that the cost per production capacity will be very competitive compared with current RAS technologies, even in much smaller scale. Modularity brings some benefits as well. Rap-up time will be shorter and gradual expansion is possible. Plug-and-play systems could be used not only in novel farms but also to increase capacity rapidly in existing farms.

“Europe is a leader in trout and salmonid consumption, and there is an obvious need for aquaculture intensification too. The European market is therefore probably the most interesting for this technology. However, simplicity, easiness of transportation and lower requirements for local infrastructure could make these systems very potential way of food production in third countries too. Also site-specific risks are lower as these units can be relocated if necessary; it secures the value of the investment. This is, of course, something new and beneficial in all markets, but especially in areas that have more site-related uncertainties.

“We have produced only rainbow trout with our prototypes so far, and as we are cold water specialists ourselves, the salmonids are natural choice for our first target. However, we are aware of other potential fish species and even shrimp as well, but other species is the area that we are looking forward to enter a bit later.”

The engine room (Photo: Natural Resources Institute)

 

 

 

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