north a f unit: methane aquaculture - auburn ...€¢two solar stills at a time heat the sludge for...

The North Auburn Fisheries unit, located in Auburn,

Alabama harvests Nile Tilapia year round. The tilapia

grow to maturity in two adjacent tanks located inside

of a greenhouse to. The winter months make it

difficult to keep the water warm for healthy growth

conditions. Monetary constraints posed by traditional

heating methods creates the need to develop a

sustainable heating system that utilizes the fish

waste at hand.

•Heat tank water from 22˚C to 25˚C through anaerobic

digestion and collection of generated methane.

•Alter agriculture digestion systems for an

aquaculture system.

•Design a completely nature powered and cost

effective system to demonstrate the potential in

green energy.

•Heat tilapia sludge from 22° to 35°C, on cloudy

and sunny days during the winter months.

•Run in batch mode for about 1 hour

•Two solar stills at a time heat the sludge for one

digester

•The solar stills will be filled 3 times a day with 24

gallons of sludge

•Top of solar still can open to allow user to push

leftover sludge into outlet

Methane aquaculture system consists of:

• 4 solar stills

• 5 fixed film anaerobic digesters

• Rain water capture barrels

• Methane burner for heating

This increases the revenue potential of tilapia by

facilitating increased tilapia growth and decreasing

the use of electrical heating. The system also creates

an opportunity to educate future generations on the

potential of sustainable energy.

Dr. Jesse Chappell, Dr. Mark Dougherty, and Dr. Oladiran Fasina.

NORTH AUBURN FISHERIES UNIT: METHANE AQUACULTUREAnnie Gallagher, Steven Major, Bobbi Steenbergen Williams

Biosystems Engineering Department, Auburn University, Auburn, Alabama 36849.

PROBLEM STATEMENT

DESIGN GOALS

Methods

SUMMARY

LOCATION MAP

PROPOSED DESIGN

Acknowledgements

SOLAR STILL DESIGN

COST ESTIMATE

DIGESTER DESIGN

Fixed Film Anaerobic Digester

•55 Gallon, 15° cone bottom tank with removable lid and stand.

•Denim insulation, and black tarp to keep digester temperature

between 32°C and 35°C.

•Fixed film of textured plastic electrical conduit pipe to increase

contact between bacteria and total solids.

•Digesters run in batch mode, with a hydraulic retention time (HRT) of

1 day, and a solid retention time SRT of 10 days.

•Slurry runs through system in updraft mode.

•System of 5 digesters produces 16 meters cubed a day.

Figure 3: Sketch up rendering of Fixed Film Anaerobic Digester.

1. Existing Features: Waste water with 2% solids flows from the Tilapia tanks to clarification basin.

2. Solar Stills: Thickened sludge (5% solids) from the hydrostatic valve are gravity fed into the solar still. The

sludge is heated from 22°C to 35°C.

3. Fixed Film Anaerobic Digesters: Fed every 24 hours with 48 gallons of sludge from the solar stills.

4. Digestate Collection: Digestate from fixed film digesters is collected in a trough to be used as fertilizer.

Figure 2: SketchUp Rendering of Methane Production System

Components Amount

Solar stills $ -254.30

Fixed Film Anaerobic Digesters $ -2.094.10

Pump and piping

(2” PVC Sch. 40 painted with white paint

for UV protection)

$ - 592.19

Cost Saved on Heating

(December- February)

$ 223.39

Increased Revenue from Fish Sold

(December- Februry)

$ 2937.00

Revenue from System Per Year $ 219.80

Table 1: Cost Analysis of system for months that water needs heating,

doe not include maitence, operation, or production

Figure 1: North Auburn Fisheries Unit located north of auburn university

on N. College Street.

Digestate Solids Trough

Liquid Digestate Collection

Educational Board

Solar Stills

Methane Storage

Water HeaterExisting Clarification Basins