Oregon’s Methane Project -Oregon’s Methane Project -Experience and PotentialExperience and Potential

Mike Gamroth

Oregon State University

Dept. of Animal Sciences

The processThe process

• Anaerobic digestion – like the rumen– Longer retention

• Methane collection

• Methane use– Heat, hot water– Combustion engine electricity

“Methane digester”

Basic conceptsBasic concepts

• Decomposition of organic material

• Oxygen-free environment

• Numerous strains of microorganisms

• Biogas– Methane 50-80%

– CO2 20-50%

– Other gases

• Ambient temperature– Covered lagoon– Lowest output

• Mesophilic– Around 100º F– More forgiving

• Thermophilic– Highest output, lower retention time

Digester typesDigester types• Plug flow

– Suited to scraped manure– Most common on dairies– Long rectangular tanks– Heat added, in-ground or insulated– Retention time (RT) 15 to 20 days

Digester typesDigester types• Complete mix

– Typically upright round tanks– Benefits from regular feeding– Can handle “wetter” manure– When co-digesting, mixing important

Digester typesDigester types• Covered lagoon

– Lowest cost, simplest to operate– Best suited to warm climates, wet manure– Lowest gas output– Often will be “seasonal”

Digester typesDigester types• Biofilm

– Can augment any digester– A place for bacterial activity– Reduces retention time

Economics 101Economics 101• A thrifty digester system can payback

in 7 to 10 years– Initial cost– Operation costs– Value of energy, tax credits– Other benefits – odor control, solids sales

Benefits of digestionBenefits of digestion• Generate energy from biomass• Odor reduction• More readily available nitrogen• Pathogen reduction

$65 $68 $80 $83

Why there aren’t more…Why there aren’t more…

• Poor design

• Lack of skills, time

• Excessive maintenance, operation time

• Diminishing returns over time

• Lack of interest

• Out of business

EPA and Meyer, et al

Keys to successKeys to success• Know your manure quality• Match the digester technology with the

manure• Select a tested design and keep it simple• Take advantage of incentives• Monitor the system daily• Line up operation and maintenance

backup

ResourcesResources

• http://www.epa.gov/agstar/index.html

• Our project:– Energy Trust of Oregon– Oregon Beef Council– Oregon Dairy Farmers Association

• Amanda Green (360) 751-4190 Amanda Green (360) 751-4190

A partnership of Cal-gon Farms A partnership of Cal-gon Farms and Portland General Electricand Portland General Electric

The systemThe system

• Scraped manure• Piston pump to feed

digester• Digester effluent

through a screw-press screen

• Liquids stored in lagoon

• Solids in covered bunker

UsesUses

• Lagoon liquids mixed with water and irrigated onto field corn

• Solids are sold off the farm and used as bedding

• Recycling lagoon liquids through separator when not used for digester

Research projectResearch project

• Questions about the farm’s nutrient balance

• Questions about the start-up and stabilization of the digester

• Received money from a grant program to sample the digester during start-up and for a two month period during operation

• Evaluate solids as a soil amendment

Electrical OutputElectrical Output

Generation Record (based on PGE bills)

Cal-Gon Farms Biogas Project

6603362716778/3/2003

676291961411/27/2002

746312311510/29/2002

59630178869/28/2002

49430148178/29/2002

38432123017/30/2002

2753185275/30/2002

Avg kWh/day# DayskWhEnding Svc Date

Cal-Gon Anaerobic DigesterOrganic Acid Levels

0

500

1000

1500

2000

2500

3000

3500

1/9

/20

02

1/1

6/2

00

2

1/2

3/2

00

2

1/3

0/2

00

2

2/6

/20

02

2/1

3/2

00

2

2/2

0/2

00

2

2/2

7/2

00

2

3/6

/20

02

3/1

3/2

00

2

3/2

0/2

00

2

3/2

7/2

00

2

4/3

/20

02

4/1

0/2

00

2

4/1

7/2

00

2

4/2

4/2

00

2

5/1

/20

02

5/8

/20

02

5/1

5/2

00

2

Sample Dates

(mg

/L)

Acetic Acid

Butyric Acid

Propionic Acid

Basic resultsBasic results

Lb. / 1000 gallons

DM % N P K CFU/100 ml E. coli

Raw manure 13.0 43 6 26 59 mill.

Digester effluent 4.6 27 4 19 1.2 mill.

Solids 26.4 6.3/t 2.4/t 3.7/t

Exporting solids to reduce nutrient loadingExporting solids to reduce nutrient loading

Lb./cow-year (3.5 ton/cow)

N P K

Avg. separated solids1 17.1 3.0 6.5

Bernie’s separated

solids

22.4 8.4 13

Bernie’s lagoon solids 31.1 14.6 9.4

1 Average of 51 separators, Willamette Valley, 1995

Solids plotsSolids plots

DAF separation

TS TSS

Raw 1.9

Sludge 3.3

Effluent 0.4 0.05

90%+ P removal