Notably, the production of fish in aquaculture systems has a lower carbon footprint per kilogram of output compared with other terrestrial animal production systems. This ultimately means that fish systems have much lower nitrogen and phosphorous outlet when compared to beef and pork production systems. Typically, fish species, such as the Atlantic Salmon, have a feed conversion ratio of about 1:1.2, which means that just over 1 kg of feed is converted to the equivalent quantity of fish meat.
The feed requirements for the production of food are therefore far more sustainable when comparing the typical feed requirements of land-based animals (beef has a typical feed conversion ratio of 1:6). Together with insects, fish are the most efficient converters of feed into a high-quality protein source. Unfortunately, fish stocks in the world’s oceans are declining fast due to overfishing. Aquaculture therefore has an enormous role to play in food security for current and future generations and is therefore commonly referred to as the new “Blue Economy”.
There are various methods of finfish aquaculture, which include:
open-net pens or “cages”, where fish are kept inside a large floating net, fixed to the bottom of a lake or sea bed
pond-based aquaculture, where ponds are either fully or semi-enclosed bodies of water and where water is filtered and treated before return to the ocean
The Recirculating Aquaculture System (RAS), as selected for the Cape Nordic Corporation Project, is such a pond-based system, where a closed environment allows for water to be treated and recirculated, with reduced wastewater discharge. In contrast, open-net pens allow for interaction between the environment inside the pen and outside the net. This means that there is a risk of waste, chemicals, parasites and diseases being exchanged between the two environments, with a possible disturbance of the local ecosystem.
RAS SYSTEM METHOD
Some of the benefits of Recirculating Aquaculture Systems (RAS) include:
Minimise any requirement for antibiotics and therapeutants resulting in the production of high quality, ‘safe’ seafood.
No requirement for predator or parasite control.
Eliminate the release of parasites and alien fish species to recipient waters.
Enables secure production of non-endemic species.
Full control over effluent waste, which can be treated before discharge.. CNC will utilise multitrophic aquaculture to create a completely independent ecosystem, allowing for the discharge of essentially clean water back into the ocean.
FLEXIBILITY IN PRODUCTION
There is flexibility in the production meaning that, in the longer term, multiple species can be farmed simultaneously.
Some flexibility in the location of the facilities allows for a site to be selected which is in proximity to markets and processing facilities.
INCREASED GROWTH RATES
Optimised feed use (superior feed conversion ratios) and increased growth rates compensate for additional energy costs associated with pumping and water purification (in comparison to open water sea cage fish farming).
REDUCED EXPOSURE TO BAD CONDITIONS
Reduced exposure of fish stock to stressful conditions, such as unfavourable weather, temperature, pollution, red tides and predation.
With the wastewater effluent purge stream generated by the RAS system, CNC aims to create a symbiotic ecosystem, which will naturally filter and consume excess food, solid waste, nitrogen and phosphorous present in the water before discharge to the ocean.
An integrated multitrophic system comprising of several complementary aquaculture species will be incorporated as part of the complete fish production facilities. The various species will be introduced such that they feed off one another, as they do in nature, creating a balance between the biological and chemical processes in the system.
THE MULTITROPHIC AQUACULTURE SYSTEM WILL INCLUDE INCORPORATION OF THE FOLLOWING SPECIES:
CNC aims to develop the fish facilities in the most environmentally-friendly manner and has considered:
- Integrated multitrophic aquaculture systems, meaning that natural ecosystems will be created to clean the final effluent purge stream before returning this to the ocean.
- Botanically-sensitive areas, which will be protected by means of facility and construction area setback, liners and cut off drains, such that there can be no influence of the multitrophic systems on the natural groundwater conditions.
- Sustainable sources of freshwater via boreholes has been carefully considered and tested by CNCs geohydrology specialists.
- Preservation of the dunes with a single dune crossing point considered at a location where environmental impact will be a minimum.
- Energy efficiency of the entire facility by means of utilising the water in the RAS systems for natural thermal inertia and thereby minimising the energy footprint of the facility.
- Generation of over 70% of the facility’s energy needs by means of renewable energy – namely wind power and solar PV. The wind turbines will be optimally located (set back from the coast) so that they do not pose a threat to migrating birds and furthermore do not result in excessive noise pollution for neighbouring farms and communities.
- Aesthetically-pleasing buildings, which will blend into the natural environment and which will have minimal visual impact.