Anaerobic Digestion: Turning One Man’s Trash Into Another

Man’s Treasure

January 20, 2009

Dr. Catherine Keske

Dr. Sybil Sharvelle

Recovering Manure to Produce Energy

• Benefits of Anaerobic Digesters

• How Digesters Work

• Trends and Feasibility

• Economic Issues

• How to Get Involved or Learn More

• Questions

Benefits of Anaerobic Digesters

Environmental

• Production– Soil management– Manure management– Biogas production

• Reduces environmental pollution– Water– Green house gases– Ammonia

Economic and Social

• On-farm energy generation (avoid electricity purchases)

• May sell energy to utilities

• Savings on bedding

• Sale of composted solids

• Carbon credits available

• Renewable energy certificates

• Odor control

Anaerobic Digestion: How It Works

High BOD Waste

Organics Acids

Acids CH4

High NutrientLow Odor

Waste

Anaerobic Environment

Cogeneration

Hot Water

CH4

Green Power

ADM Soybean Processing

Biodiesel Plant

Anaerobic Digester

Frito Lay

Hot Soybean Oil

Cold Soybean Oil

Hog Waste

Food Waste

Green Power

Model Project: Quadra Project in Indiana

WE Can Do This in Colorado Too!

Waste Suitablility

• Low solids content, < 14% solids

• Low inorganic content– Soil– Rocks

• Higher organic content, more energy content

Colorado – Cold Climate

Average Annual Minimum Temperature

Covered Lagoon – Not an Option

Colorado – Dry Climate

Average Annual Precipitation In Colorado

Need to Find Nearby Source of Wastewater or Add Groundwater to Waste

Successful Digester at Dairy in Montana

Alternative Design - Two Stage Leachate Collection

Low MoistureManure and

Other Waste

Organics

High Organic Leachate Anaerobic Digester Methane Gas

Costs of Anaerobic Digesters

• Cost of the digester:

Approximately $1 million

Average life: 15 yrs. (Range: 10-20)

• Cost of the solids separator:

Approximately $75,000

**Key to raising profitability**

• Opportunity cost

Cost of your next best alternative

Are Digesters Profitable? “Yes…”

• Several models show profitability– Measured in cash flows associated with the

investment

• Critical to use a solids separator– Use the solids as a co-product– Bedding is the most economic use

• Larger herds lead to economies of scale

• Key element to profitability: Energy prices

“…But…Will a Digester Work for My Operation?”

• Greater than 500 head (more than 1,000 head preferred)

• Requires steady flow of manure (CAFOs)• Climate matters – the warmer the better• Must be able to use the biogas• “Community” digesters are an option

– Pipelines transport waste to central site– Could consider other facilities (e.g. food

processing)

“Yes, But…”Economic Considerations

• Majority of studies conducted in the East

• Profitability relies on carbon credits– $2 per metric ton of CO2

• “Net positive gain” may include a net gain to the environment (not necessarily a net gain to the farmer/rancher)

• Profitability critically depends upon energy prices

Want to Learn More?

• Contact Us!

• Institute for Livestock and the Environment: http://ile.colostate.edu

• USDA Producer Workshop

2/19/09 York, Nebraska

• AgStar: http://www.epa.gov/agstar/

• Colorado Governor’s Energy Office:

http://www.colorado.gov/energy/index.asp

Sponsoring feasibility studies

Questions?