covered anaerobic digester

Covered Anaerobic Digester

Developing an Environmental Management System (EMS) Approach for Agriculture and

Agribusiness Dec. 18, 2000

Julian Barham

Barham Farms

Zebulon, NC

Case Study - Barham Farm

• Located - Johnston County, NC

• modern swine farm• populated in 1994• owned and managed

by Julian and Elaine Barham

Background Information

• 4000 sow - farrow to wean• 4 gestation barns• 2 farrowing barns• slatted floors (grates)• shallow pit/recharge• flush pit 4/8 day cycle• waste gravity flow

Process Diagram

1994 - 1996 Effluent from barns to anaerobic lagoon

40,000 gallons/day (total solids < 1.0%)• lagoon surface = 6 + acres

Traditional Anaerobic Lagoon Design

Freeboard

Rainfall/Storms

Storage

Treatment

Sludge

FieldApplication

Evaporation Emissions

Covered Anaerobic Digester ?

1 Odor Control 2 Energy Resource3 Ammonia Emissions4 Rainfall Exclusion (*)

Anaerobic Digester and Storage pond

Treatment

Sludge

Biogas

Anaerobic Digester Storage Pond

Rainfall

Digester effluent

Lagoon Cover Design

• partial cover ?

• bank to bank ?

lower cost (?)

rainwater into lagoon

odor reduction

high maintenance

rain exclusion

no emissions (sealed)

biogas storage

low maintenance

Partial Cover - Practical Application !

Bank to Bank Cover - Practical Application

Things Involved

Biogas• Methane + CO2 + H2S• Greenhouse gasOptions• Flare• IC Engine• Micro Turbine• Burner/Boiler

Equipment NeededBoiler for hot water

- 10,000 gallon hot water storage

- hot water for space heating and mats

Engine for co-generation

- 120 KW for peak shaving

- engine heat recovery - hot water

Lagoon PerformanceBarham Lagoon Performance

0

200

400

600

800

1000

1200

1400

1600

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec1997 & 99

Bio

gas

Yiel

d (c

u.ft.

/hr.)

30

40

50

60

70

80

90

100

110

Predicted BiogasMeas.Biogas 97Meas.Biogas 99Predicted Temp. Meas. Temp. 97Meas. Temp 99

Lago

on T

empe

ratu

re (F

)

** readings middle of month

estimated data pt.

Covered Anaerobic Digester Effluent

Organic Carbon - reduced 85%

TKN - reduced 30%

Total P - reduced 75%

K - reduced 20%

Ref: ASAE Proceedings

8th InterNatl Symp.

Oct 2000

Eval. of Alternat. Waste Sys.

Digester Effluent Use:

Apply at agronomic rate to low value hayland!

Digester Effluent Use:

Nutrient rich for high value produce in green house environment!

Benefits Seen

Biofilter - low energy input process

Reduce Ammonia Emissions (NH4 to NO3)

Lower pH

Greenhouse

Other Results and ConclusionIt’s not

“A Sows Ear to a Silk Purse”

but

Demonstrated

Energy Resource

Reduced Emissions

Marketable Produce

Manageable System

?