Scotland's first floating semi-closed fish pen begins to take shape
The enclosure is being assembled at trout farmer Loch Alba Group's site at Ardnish, Loch Ailort
Trout farmer Loch Alba Group has begun installing the first Gael Force SeaQureWell floating semi-closed containment pen at its Ardnish site on Loch Ailort.
The pen won’t be stocked until all systems and controls are fully assembled, functioning and tested. Loch Alba’s team want to ensure they can manage and control all systems and the environment inside the SeaQureWell before moving the first fish into it.
“We have the floating collar for the first SeaQureWell installed and we will now spend the next few months rigging it with the bag and all of the systems and the pumps and control systems,” said Stewart Graham, who owns both Gael Force Group and Loch Alba Group.
Essentially, we could be farming up to 3,000 tonnes of biomass at Ardnish in a rolling 12-month period, with a significantly lower impact on the environment than the 300 tonnes currently consented in the old open net pens on the site
“Essentially, we want to ensure we have an environment that is as we expect and that we can control. When we're satisfied with that and all systems are running reliably and robustly, we’ll put the fish in.”
90%-plus waste capture
Gael Force began designing and developing the SeaQureWell in 2022. Like some other floating semi-closed containment systems that have been developed elsewhere, the SeaQureWell houses fish in an impermeable bag suspended from a cage collar. Water is drawn from below the level where sea lice are most likely to be found, and is discharged after being filtered. There is complete water exchange every 50 minutes.
The big difference between the SeaQureWell and other semi-closed systems is that, according to modelling, the SeaQureWell will be able to capture more than 90% of waste. The ability to remove a high percentage of sludge will be crucial to the success of the SeaQureWell, because deposition of fish faeces and uneaten feed on the seabed is a key factor in limiting the maximum biomass of fish that open net pen farms can stock.
Capturing 90% of waste could potentially allow a farm that has a limit of 300 tonnes for open net pens to instead stock 3,000 tonnes in SeaQureWells, said Graham.
Consent for one Well
The waste capture modelling was carried out using third-party propriety certified software, and the results impressed Scottish government regulators, he added, although it has still to be proven in the water.
“We say waste capture of 90% and over, but we will also stress test at 75% to ensure there’s the carrying capacity [on the site] and then we will monitor.”
Loch Alba Trout has consent for one 22,000 cubic metre SeaQureWell – big enough for 800 tonnes of fish - at Ardnish, and plans three more at the site. It bought the site off Mowi Scotland, along with two trout hatcheries - at Kinnaird near Montrose, and Frandy, near Auchterarder - and a freshwater grow-out site at Loch Earn.
“We believe we will get the required consents, which will mean that essentially we could be farming up to 3,000 tonnes of biomass at Ardnish in a rolling 12-month period, with a significantly lower impact on the environment than the 300 tonnes currently consented in the old open net pens on the site,” said Graham.
600g juveniles
Loch Alba will stock 600g fish, and harvest them at 4kg in under a year.
“We are proposing to have staggered stocking intervals, stocking every 13 weeks into individual Wells, and that will mean that our peak biomass at any one time is considerably lower than the total biomass produced in any 12-month period,” explained Graham.
The company’s production forecasts are based on an eventual peak stocking density of 40 kilos per cubic metre, which is two and a half times the 15kg/m³ density used in Scotland’s open net pens.
Initially, Loch Alba will stock at 20 kg per cube, then 30kg/m³, and finally 40kg/m³.
Stocking density
Graham has no fears that a more densely stocked pen will create welfare issues.
“First of all, if you take the mechanical capability of the system, we've designed for 50 kilos per cube, with redundancy and headroom at that. We are suggesting an operating level of 40. So, from a system point of view we have no problem coping with that. In addition all systems have at least 100% redundancy, too,” he said.
“From a natural point of view in terms of how fish shoal and how much of the volume is available to them that they're using at that level, we don't see any problem.
“You might think we would have issues, for example, in some of the certification which has a 15 or 17 kilo per cube cap on it.
“But what’s driving that is the environment’s ability to sustain that stocking level of fish due to the available oxygen in the ambient current, whereas we are oxygenating and controlling the minimum and maximum levels of oxygen we will have inside the Well, providing the right environment and demonstrating the survival rate. RAS (recirculating aquaculture system) facilities, which this effectively is at sea, are already operating at higher stocking densities than these levels.
“We are already engaged with certification bodies and we don’t see that that will be a blocker at all.”
A useful by-product
Graham views the sludge that will be removed from the SeaQureWells as a resource, and Gael Force has been working on ways to process it for different purposes such as biofuel and fertiliser.
“The equipment used is manufactured by third parties, but we believe we will have significant intellectual property around what’s required to bring it from a 1%-solid sludge through to a 90%-solid, dry product coming out the other end.
“We plan multi-stages of dewatering, filtering, pressing, drying, all parts of that process. We're not going down the pyrolysis route. Given that we’re producing all our own power on the site with generators, we have a lot of heat that we’re looking to shed and our idea will be to use that heat into the drying process, in the final drying of the sludge as it becomes a dry matter product.”
Graham is looking at the SeaQureWell from two perspectives: as the owner of the company that aims to sell the SeaQureFarm system to fish farmers, and as the owner of Loch Alba Group.
“From a Gael Force perspective, we see the target market in two areas. One is for post-smolt from which you will supply open net pens in higher energy sites for hopefully single-summer grow out,” he said.
“The other is for lower energy sites that currently cannot sustain high levels of biomass in an open net pen format. If we can demonstrate that we can capture 90+% of waste and you have a current 500 tonne consent, theoretically we should be able to take up to 5,000 tonnes grow-out on that site providing the environment can absorb the dissolved nutrients produced. So, that means some of these inshore sites which may not currently be viable in an open net pen configuration may very well be viable for grow-out.”
Six subsidiaries
That approach is already being taken by Loch Alba Group, which has created six subsidiary farming companies – SeaQureFarming 1 through to SeaQureFarming 6 – to pursue semi-closed farming at new sites, most likely for salmon which they hope will be in partnership with existing producers.
“The initial scoping is all done for these sites. We have four of the leases in place already. And the scoping exercise has been done for these. It’s quite likely at least one or two of them will be a post-smolt site. And possibly up to three or four of the others could possibly be grow-out sites,” said Graham.
