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