Converting Dairy Manure into Energy. An introduction to anaerobic digestion of farm waste Stefan Grimberg Associate Professor Dept. Civil Environ. Eng Clarkson University

Thank you to Floyd Schanbacher

Anaerobic Digester Potential Benefits Odor Control Reduced liability Manure stabilization Help with nutrient management Soil stability Energy generation Offset farm electricity requirements from grid Sale of extra energy Heat generation to reduce fuel required Reuse of bedding solids Offset bedding cost

Odor Control

Reduced liability

Manure stabilization

Help with nutrient management

Soil stability

Energy generation

Offset farm electricity requirements from grid

Sale of extra energy

Heat generation to reduce fuel required

Reuse of bedding solids

Offset bedding cost

Plug Flow Digesters Little mixing Few mechanical parts Simple

Little mixing

Few mechanical parts

Simple

Mixed Digesters Mechanical mixing in tank More gas production Slightly higher capital cost

Community Digester Behringen co-fermentation plant in Germany

Digester Feed

Large-scale Digester Performance

Capital Cost of Manure Management Technology Source: AgStar Publication:

Digester economics Dr. Fick’s estimated fixed of $660 per cow is a little low for the farms we are looking at. Tinesdale farm (in Minnesota), with1800 cows, invested about $1,000 per head. Good estimate $1,000 per cow? At this capital assumption AD system become economical based on sold energy alone at power sale price of $0.09/kWh. (Mehta, 2002)

Dr. Fick’s estimated fixed of $660 per cow is a little low for the farms we are looking at.

Tinesdale farm (in Minnesota), with1800 cows, invested about $1,000 per head.

Good estimate $1,000 per cow?

At this capital assumption AD system become economical based on sold energy alone at power sale price of $0.09/kWh.

Case Study Gordondale Farms, Nelsonville, WI 750 head dairy Sell biogas to utility that generates electricity on site, utility owns and operates generator Sell at 0.015 $/kWh generated Martin, J.H., 2005. An evaluation of a mesophilic, modified plug flow anaerobic digester for dairy cattle manure. Final report for EPA contract GS10F-0036K

Gordondale Farms, Nelsonville, WI

750 head dairy

Sell biogas to utility that generates electricity on site, utility owns and operates generator

Sell at 0.015 $/kWh generated

Summary

Martin, 2005

Martin, 2005

Martin, 2005

Martin, 2005

Martin, 2005

Martin, 2005

Martin, 2005

Martin, 2005

Economic Evaluation Capital costs with co/gen: $748,000 Annual sale of power: $18,396 Avoided annual bedding cost: $60,000 Sale of extra solids: $8,600 Total benefits: $86,996 Payback period: Approx 6 years.

Capital costs with co/gen: $748,000

Annual sale of power: $18,396

Avoided annual bedding cost: $60,000

Sale of extra solids: $8,600

Total benefits: $86,996

Payback period: Approx 6 years.

Digester Systems Model Digester Solids Sep. Cogen Manure Other Input Biogas Electricity offset Surplus electricity Surplus heat Spread liquid fraction Solids for bedding Sale of solids Solids field application Heat

Example 500 cow dairy Free stall barn Scraped manure Include flush from milking parlor Northern NY

500 cow dairy

Free stall barn

Scraped manure

Include flush from milking parlor

Northern NY

Model Estimate: 500 cow dairy -$1.8 Annual Net Benefit per Cow without excess heat and methane credits $13.54 Annual Net Benefit per Cow if excess heat cannot be sold $38.27 Annual Net Benefit per Cow $111,463 Total Annual Benefits $10,000 Onsite Fiber value $16,739 Tax Offset $8,495 Farm savings-Thermal (internal) $25,171 Farm savings-Electric (internal) $4,203 Renewable Energy Tax Credit $7,646 Methane Credit $12,368 Thermal Sales (surplus) $17,707 Electric Sales (surplus) $9,133 Fiber sales Potential Annual Benefits $23,553 Maintenance, Repair Annual Operating Costs $68,774 Total Annual Cap. Cost over 10 yrs $656,180 Digester/Cogen system Capital Cost Cost/Benefit Item

Run Digester Model Demonstrate: Effect of size Power cost Bedding off set Any scenarios of interest?

Demonstrate:

Effect of size

Power cost

Bedding off set

Any scenarios of interest?

Conclusions Anaerobic digestion of manure has significant potential to decrease fossil fuel use in rural areas. Community digesters may be very cost effective due to larger scale and mixed feed composition

Anaerobic digestion of manure has significant potential to decrease fossil fuel use in rural areas.

Community digesters may be very cost effective due to larger scale and mixed feed composition