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By Dr Mark Burdass
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The Potential for Recirculation Aquaculture
Dr Mark Burdass
Recirculation Systems
• Systems used worldwide• Production capacity depends on treatment
system• Defining Recirculation Systems:
– System that recycles and renovates water for the culture of aquatic organisms!
Global Perspective
• Successful large scale recirculation aquaculture facilities in UK, Norway, Europe, US, Canada & Australia.
• Highly intensive recirculation facilities used in Scotland to produce salmon smolts
Definition
• Original definition 95% recycle (based on flow), means 5% exchange per pass
• More recent systems defined by daily volumetric exchange rates (10% per day)
• Lots of challenges with systems recirculating water at < 5% per day
Advantages• Controlled Environment
– Controlled temperature environment– Allows controlled product growth rates– More efficient food conversion– Predictable harvest routines– Allows production all year round– Biosecurity advantages– Enclosed environment means production free of
predators and other damaging wildlife– Allows efficient inventory control
• The systems designed to conserves heat and water through water reuse– Reconditions the water through filtration processes
• Allows effective economies of scale– This results in high production per unit area– Save on handling equipment as used more
intensively.
Advantages• Environmentally sustainable
– Use up to 99% less water than a conventional aquaculture facility
– Less than 1% of the land area– Allows waste to be managed in an
environmentally safe manner– Allows waste to be further processed or used
for hydroponics– Producing tropical fish locally has low carbon
footprint because of low food foodmiles in production
Advantages• Not restricted to traditional aquaculture
production locations• Not restricted to traditional UK aquaculture
species– Species such as barramundi, tilapia and
catfish possible in UK• Allows production to be placed near to
market
Why Recirculation Systems• Challenges
– High Initial Investment• Compared to other production methods
– Financing can be an issue because investors often want fast returns
– Technology is not well known• Getting better
– Very short response time– Reliability of electricity supply critical– Lack of track record
• Failures common• Hard to finance
Challenges• Not as yet able to compete with large
scale aquaculture production• Most Recirculation farms are under 500
tonnes in size• Don’t have the economies of production
volume– Supermarket product volume requirements
often above production of a single unit
Other Challenges• There have been a number of high profile failure
in UK and across Europe• Often difficult to determine why they failed,
however:• The reasons are various but have included:
– Technology was labour intensive and therefore running costs were too high
– Poor Design• Often under-capitalised
– Poor management decisions– Over optimistic market forecasts for product sales– Inexperienced staff
System Comparison
• Conventional intensive tilapia farm
• 17.4 tonnes per ha per year
• Water use: 21 m3 per kg of production
• Recirculation tilapia farm
• 1,340 tonnes per ha per year
• Water use: 0.5m3 per kg of production
Uses for Recirculation Systems• Hatchery• Nursery• Quarantine• Advanced fingerling production• Purging market sized product• Grow-out table production• Near market site holding system
Running Costs• Food and labour are the still the two main
costs• Heating and pumping often amount to less
than ¼ of the above• Initial capitalisation is a very significant
cost compared to conventional aquaculture
• Possibility for large units of using renewable energy supplies thereby reducing costs in the long term
Systems• High Stocking densities do not constitute
an efficient recirculation system!• High feed rates per day do!• It takes feed to grow fish!• Food is the main consideration when
designing and predicting the capacity of a system.
• An intensive recirculation system has a high capacity to grow fish rather than hold them
Technology
• The technology has been available for over 30 years
• Reliable• Efficient• Most failures are down to mismanagement
of systems or producing inappropriate species
Filtration System must:• Remove solid wastes
– Settleable, suspended and dissolved• Convert ammonia and nitrite to nitrate• Remove CO2
• Add oxygen• Maintain acceptable pH• Control Pathogens• Keep up with the generation of waste
Recirculation Process Diagram
BIOFILTER NH3 REMOVAL CO2 REMOVAL
O2 ADDITION
O3 ADDITION
O3 MONITOR
OZONEDESTRUCTION
BY UV
CULTURE TANKS
SEPTIC TANK
DRUM FILTER
PUMP SUMPFILTRATE
CLEAN WATER FROM UPPER LEVEL IN TANK
(SIDE BOX) 85%
AIR BLOWER
BOTTOM DRAIN15%
SWIRLSEPARATOR
BOTTOM DRAIN15%
SLUDGE TO WASTE
MAKE-UPWATER
Key Water Quality Parameters
• Dissolved Oxygen• Ammonia-Nitrogen (NH3 & NH4
+)• Nitrite-Nitrogen (NO2
- )• pH• Alkalinity• Carbon dioxide (CO2)• Nitrate-Nitrogen ( NO3
- )
Misperceptions
• Overly complicated• Prone to catastrophic failure• Only suitable for high value species• Needs highly educated staff to run
Key Issues for success• Use proven technology in system
construction• Ensure system has effective monitoring
systems• Build in back up systems to key processes• Most success has come from small units
which have scaled up• Use species with a track record in
recirculation systems• Be sure of the market
Key Issues for success• Business plan assumes market prices will
drop once production starts• Grow species with a short production time
to improve cash flow• Ensure product is fit for market• Ensure have the trained staff to operate
the systems
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