1. Cow Power
Amy Urling

2. History of Cow Power
2004: CVPS (now Green Mountain Power) starts using cow power at Blue Spruce Farm in Bridgeport, VT (Seedstock.com)
2006: Second farm (Berkshire Cow Power) in VT starts generating cow power (Seedstock.com)
2007: Third farm (Green Mountain Dairy Farm) in VT starts generating cow power (Seedstock.com)
2009: The number of CVPS customers using cow power increases to (Wang et al, 2011)
2010: The EPA estimates U.S. cow power is producing 340 million kwh of electricity (Wang et al, 2011)
2010: The EPA and USDA signed an agreement to advance the implementation of cow power digesters (AgStar, 2010)
2013: 18 digesters in VT (Seedstock.com)

3. How it Works
Farmers take the cow manure and feed it into an anaerobic digester on the farm. The digester is built to hold 21 days worth of farm waste at roughly 100°F. Bacteria in the digester convert the waste into various products, one of which is methane gas. The gas produced by the bacteria is then delivered to a modified natural gas engine. The biogas fuels the engine, which in turn spins an electric generator to create electricity. Heat generated from this process is repurposed to keep the digester warm, which offsets fuel purchases on the farm. The energy generated is then fed into the electricity grid for distribution to customers. The left over digested manure is processed through a mechanical separator and can be used to replace sawdust or sand as bedding for the animals. Solids not used for bedding may be further processed and sold as fertilizer. (GreenMountainPower.com)

4. Energy Transformations
Sun shines (radiant) Grasses grow (chemical) Cows eat and digest grasses (mechanical and chemical) Cows poop (mechanical) Poop is put in a digester (mechanical) Bacteria convert poop to methane (chemical) Gas spins an electric generator (mechanical) Electricity is produced (electrical)

5. Raw Materials Raw Material = Cow Poop Farms with digesters
Potential for Cow Power

6. Cost, Reliability and Efficiency
Cost = 10 cents per kwh (Blue Spruce Farm, 2011)
Reliability = Very reliable; cows always poop
Efficiency = 60% - 70% (Lawson)

7. Advantages
Renewable
Electricity can be used on the farm and sold back to the grid
Locally available
Methane is trapped instead of going into the atmosphere as a greenhouse gas
Better manure management than open lagoons
Left over solids are used to make cow bedding which saves the farmer money

8. Disadvantages Cows can create water pollution and soil erosion
The land cows live on has to be open, so trees may need to be cut down
To set up the cow power system, farmers have to rely on loans and grants
Electricity is more expensive (customers have to pay 4 cents more per kwh)

9. Environmental Effects
Air Pollution: The methane (CH4) from cow poop is a powerful greenhouse gas. Cow power traps some of the methane so it doesn’t go into the atmosphere.
Mining: None
Habitat Disturbance: Cows need open land, so trees may be cut down. Cows are usually fenced in.
Renewable

10. Cow Power in Vermont
Cow power is definitely increasing in VT. There are currently 18 digesters in VT each producing about kw per day
PBS video about Cow Power in Vt:
(Agstar, 2011)

11. Cow Power Example
Woodchuck Cider Mill in Middlebury, VT (Woodchuck, 2013)
Monument Farms Dairy has 500 cows
Woodchuck gets 25% of its electricity from the farm

12. Other Interesting Facts
One cow produces over 30 gallons of manure a day (
For every kwh of electricity produced from biogas, there is a net reduction of 414 g of CO2 emission. (Agstar, 2010)
CVPS had the first manure-to-energy program that helps run an environmental college (Green Mountain College), a local Brewery (Long Trail Brewing Company), an office of the US Forest Service (in Rutland), a National Park (Marsh- Billings-Rockefeller National Historic Park in Woodstock) and New England's largestAlpaca Farm! (Cas-Cad-Nac farm)! (Blue Spruce Farm, 2010)
Fibers recovered for animal bedding save farmers $100,000/year (Blue Spruce Farm, 2010)

13. References
AgSTAR | US EPA. (2010). Retrieved from
Blue Spruce Farm. (2011). The Condor, 113(1).
Green Mountain Power. (n.d.) Retrieved from works/#sthash.Jfc5vUsj.dpuf
Lawson, Tom (n.d.) Overview of Anaerobic Digestion and Digesters. Retrieved from
Vermont Cow Power Program Makes Most Out of Manure, Benefits Farmers and Environment. (n.d.). Retrieved from environment/
Wang, Q., Thompson, E., Parsons, R., Rogers, G., & Dunn, D. (2011). Economic feasibility of converting cow manure to electricity: A case study of the CVPS Cow Power program in Vermont. Journal of Dairy Science, 94(10), doi: /jds
Washington.edu (2012). Retrieved from
Woodchuck. (2013). Cow Power, Turning Manure into Energy. Retrieved from power/