Waste-to-energy Anaerobic Digestion - Continued

After finding the little video that shows the basics of how this process - an alternative to a Fibrowatt plant - works, I also found a second article that offers a pretty thorough look at digesters.  This one, entitled, Anaerobic Digestion of Animal Wastes: Factors to Consider, and written by John Balsam and Dave Ryan, can be found at http://attra.ncat.org/attra-pub/anaerobic.html.  The article emphasizes farm-scale installations of the digester technology, types of systems, and practical considerations; there are also some additional references to other case studies.

The photo here is from a Wikipedia article, which you can find on the seach "poultry farming in the United States."

For highlights, it lists some of the benefits of using the digester process for electricity...

• A well-insulated, three-bedroom home that requires 900,000 Btu/day for heating in cold weather could be served by 50 dairy cattle, 600 hogs, or 7,870 layers (assuming that around 35 percent of the biogas produced will be used to maintain the digester’s temperature).
• A dairy using the national average of 550 kWh/cow/year could generate 70 percent of its electrical needs with biogas (assuming 20 percent generator efficiency and that around 35 percent of the biogas produced will be used to maintain the digester’s temperature).
• A swine operation that uses about 55 kWh of electricity and 5.75 gallons of LP gas per hog per year (including feed mill and incinerator) could supply 40 percent of its energy needs with biogas (assuming 20 percent generator efficiency and that around 35 percent of the biogas produced will be used to maintain the digester’s temperature).

The article outlines the risks of this process, including the components of the biogas, which are worth taking a look at, then goes into some practical information about how to size the installation, along with factors to consider:

• The specific benefits to be derived
• The number and kind of animals to be served
• Where the system might be placed
• How the manure and other inputs will be collected and delivered to the system
• How the required temperatures will be maintained
• How all the risks associated with the process, some of which are substantial, will be mitigated
• How the outputs will be handled
• The amount of monitoring and management time required

The article closes with a nice cost-benefit calculation of two farm-scale installations:

• Barham Farm: Covered Lagoon, costs $289,474, revenue $46,000 per/year
• Martin Family Farm:  Covered Lagoon, costs $95,200, revenue $16,000 per/year

So perhaps I should append this information to my discussion of the economic impacts to farmers - here is a process that actually would return revenue to the family farm, rather than ratcheting up costs. For reference, here is a post on the Fibrowatt squeeze on local farmers:  http://hburgnews.com/2010/04/29/fibrowatt-the-farmer-squeeze/