adapting aquaponics systems for use in the american pacific islands

8/8/2019 Adapting aquaponics systems for use in the American Pacific Islands

1/23

Adapting aquaponics systems for

use in the American Pacific Islands

Adam Baker and Harry Ako

Department of Molecular Biosciences and BioengineeringUniversity of Hawaii at Manoa


2/23

Aquaponics systems are environmentally

friendly and productive

Feed eat feed and release

metabolites, which bacteria

remediate, and plants take up

2 crops from 1 input

No effluent (negligible

environmental impact)

Productivity 6 times

higher than soil

agriculture

Plants take up

metabolites to grow

Bacteria remediate

toxic N species

bioremediatedwater

Fish grow and excrete

metabolites

cleaner water

Feed


3/23

http://rps.uvi.edu/AES/Aquaculture/basil2002.jpg

Research began in the 1970s

Plants in raceways, fish and equipment under black tent

The most well known system was developed

by James Rakocy


4/23

Uses complex equipment Requiring:

A large capitalinvestment

Constant electricity

A trained staff tooperate and maintain

May explain the lack ofcommercial aquaponicssystems

Was attempted and failed

in Saipan

This system is complicated

clarifier

degassing tank

sump

screen filter tank

Air pumps, water pump, and

237 air stones (not shown)

fish tank


5/23

The hypothesis and approach of this work

Estimates of nutrient uptake and a deeper understandingof culture water nutrient dynamics are required for design

criteria, Rakocy and Hargreaves, 1993

Lettuce require specific quantities of nutrients to grow

Fish grown under a specific set of conditions (feed

input and stocking density) can provide these

nutrients A mechanically simple aquaponics system could be

developed after these parameters are defined


6/23

Determination of lettuce nutrient needs

Nutrients

Hydroponics

nutrients

provided

Remaining

after 4

weeks

Remaining

after 6

weeks

Manganese (mg) 307 2% 1%

Nitrogen (g) 33 70% 5%

Potassium (g) 53.7 74% 14%

Calcium (g) 31.1 83% 51%

Magnesium (g) 16.1 91% 53%

Phosphorus (g) 11.2 90%45%

Iron (mg) 337 123% 83%

Zinc (mg) 77.7 97% 62%

Copper (mg) 55.5 61% 56%

Boron (mg) 322 86% 59%

Provided lettuce with

hydroponics nutrients

Measured the nutrients

remaining in solution at an

intermediate (4 weeks)

and full (6 weeks) grow out

cycle with ICP-AES

Nutrients taken up at full

cycle were hypothesized to

be required nutrients (will

be used in future slides)


7/23

Verification of predicted lettuce needs by

amount

NutrientsRequired

nutrients

Provided to Low

Ca and MgManganese (mg) 305 307

Nitrogen (g) 31.6 33.3

Potassium (g) 46.0 53.7

Calcium (g) 15.2 18.8

Magnesium (g) 4.72 6.97

Phosphorus (g) 6.12 11.2

Iron (mg) 58.1 688

Zinc (mg) 29.6 77.7

Copper (mg) 24.6 55.5

Boron (mg) 133 322

Required nutrients in first column, those provided in second columnLow Ca and Mg predicted to be adequate

No difference in yield

0

50

100

150

200

Lettuce head weight (g)

Control Low Ca and Mg

Mean lettuce head weights (g)

aa


8/23


amount

Nutrients Requirednutrients

Provided toHigh N

Manganese (mg) 305 307



Calcium (g) 15.2 31.1Magnesium (g) 4.72 16.1


Iron (mg) 58.1 688

Zinc (mg) 29.6 77.7

Copper (mg) 24.6 55.5

Boron (mg) 133 322

High N predicted to exceed needs

Greater uptake observed but no benefit in yield, even under

higher light

a a

b b


Spring Summer


9/23


amount

NutrientsRequired

nutrients

Provided

to Low KManganese (mg) 305 307



Calcium (g) 15.2 31.1

Magnesium (g) 4.72 16.1


Iron (mg) 58.1 688

Zinc (mg) 29.6 77.7

Copper (mg) 24.6 55.5

Boron (mg) 133 322

Lowered K level should be inadequate

Significant reduction in yields

ab

Control Low K



10/23

Verification of predicted lettuce needs

through time

1/4th nutrients, Week 4 Control, Week 4

Lettuce provided nutrients relative to control

Nutrient depletion was predicted at Week 4

Significantly lower yields at Week 4


11/23

Lettuce provided nutrients

relative to control

Nutrient depletion was

predicted at Week 6

Significantly lower yields at

Week 6


a

b

Control nutrients

Verification of predicted lettuce needs

through time

Predicted levels of required nutrients seem accurate in

terms of both quantity and as a function of time


12/23

Footnote: Supplemental Fe was required

Supplemental Mnwas not required

Control,

Week 3

Aquaponics

(no iron) Week3

Aquaponics,

Week 4

Fe chelate

0

100

200

300

400a

a

No Mn addedMn added



13/23

Determination of conditions to produce

nutritious fish water

Nutrients

Required

nutrients

(g)

Required from

20 L fish water

mg (mg/L)

Manganese 0.310 7.20 0.36Nitrogen 31.6 752 37.6

Potassium 46.0 1100 54.8

Calcium 15.2 362 18.1

Magnesium 10.6 252 12.6

Phosphorus 6.12 146 7.28

Iron 0.058 9.80 0.49Zinc 0.030 0.72 0.036

Copper 0.025 0.60 0.030

Boron 0.130 0.30 0.015

Calculating target levels

Derived necessary daily

provisions

Assumed that these would be

met with a 20 L daily exchange

Converted to concentrations

Experimental set up

Stocked tilapia in a 200 L tank,removed 20 L of water daily

Periodically added fish

Monitored water chemistry and

feed inputs For a tray of 48 lettuce heads


14/23

Fish water met lettuce needs

Nutrients

(mg/L)

Daily

requirement

from 20 L

(mg/L)

Fish water

14 g

feed

daily

20 g

feed

daily

40 g

feed

daily

Manganese 0.36 0 0.002 0.001

Nitrogen 37.6 30 34 47

Potassium 54.8 101 100 105

Calcium 18.1 22.5 46.2 33.9

Magnesium 12.6 13.5 18.6 21.0

Phosphorus 7.28 4.46 6.36 10.7

Iron 0.49 0.001 0.011 0.038

Zinc 0.036 0.01 0.021 0.095

Copper 0.03 0.04 0.02 0.059

Boron 0.015 0.05 0.09 0.079

Required concentrations in

first data column

Fed 14 or 20 g of feed per day,

several nutrients were deficient

Fed 40 g of feed per day

however, nutrients were

sufficient

Another consequence is that

nitrogen may be used as a

proxy for all nutrients


15/23

Required fish parameters

TankNitrate N

(mg/L)

Daily feed

input (g)

Tilapia

biomass (kg)

1 44 59 2.5

2 49 54 2.5

Nitrate N

(mg/L)

Daily feed

input (g)

Tilapia

biomass (kg)

47 40 2.3

Repeated with replication, 5 weeks in duration

Sustained target nutrient concentrations under the following conditions

Numbers were relatively close and systems were sustainable

For a 200 L tank with 20 L daily water removalMet target nutrient concentrations (47 mg/L nitrate-N) with the

following conditions


16/23

A simplified aquaponics system:

Lettuce yields as good as hydroponics

When fish water nutrients were adequate, lettuce growth

matched hydroponics controls


a a

bc c

b

d


17/23


Fish growth parameters

Tank

Fish

recovered/

stocked

Mean

weight (g)Fish biomass (kg) Feed

input

(kg)

FCR

Start End Start End Gained

T1 51/51 66 114 3.4 5.8 2.5 4.8 1.9T2 48/48 71 132 3.4 6.3 2.9 4.7 1.6

During the 10 week aquaponics trial, fish growth was measured

These can be used to predict fish yields in aquaponics


18/23

Tank

Fish

biomass (%)

Lettuce

biomass (%)

Denitrification

or solids (%)T1 26 40 34

T2 32 41 27

T3 22 49 29

Mean 27 43 30

Of total nitrogen input into the system as feed:

27% is recovered as fish flesh

43% is recovered as lettuce biomass

30%, a relatively small fraction, is lost

(as nitrogen gas or as solids used to fertilize garden plants)None was released as effluent


Aquaponics is environmentally friendly


19/23

Scenarios. Single family size

Other designs are permissible as long as

the basic specifications are followed. Fish

under the plants, water flows, etc.

Components

1 lettuce tray (2.7 m2)

1 fish tank (200 L)

1 small air pump

Specifications

Water transfer manual

Cost of construction 250 USD

Fish biomass 2.5 kg

Daily feed input 40-59 g

Production 1.4 lettuce/day and1.0 kg tilapia/5 weeks


20/23

Scenarios. Micro-farm size

Components

8 linked lettuce trays1 fish tank (1,600 L)

1 small air blower

Specifications

Water transfer air lift pump

Fish biomass 19.2 kg

Daily feed input 0.32-0.47 kg

Production 3,300 lettuce

and 80 kg tilapia/year

Construction costs 2,500 USD

Projected income 8,600 USD/year at Hawaii farm gate prices


21/23

Scenarios. Small farm, 0.1 hectare

Components

Equivalent of 270 lettuce trays54,000 L fish tank volume

1 air blower

1 water pump

Specifications

Water transfer water pump

Fish biomass 648 kg

Daily feed input 11-16 kg

Production 133,000 lettuce

and 2,700 kg tilapia/year

Cost of construction


22/23

Summary

Fine tuned lettuce nutrient requirements Set fish parameters that provide optimal nutrition

to plants

Verified results in several aquaponics trials

Eliminated all electrical components but aerationin fish tanks

Identified rational parameters that will allow forflexible aquaponics design to accommodate

different needs and physical environments Described a simple methodology that can be

applied to grow other crops aquaponically


23/23

Thank you

This work was funded by the United States Department ofAgriculture (USDA) Center for Tropical and Subtropical

Aquaculture (CTSA) through Grant No. 2004-38500-14602

adapting aquaponics systems for use in the american pacific islands

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