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Reprinted, with permission, from the proceedings of: Mitigating Air Emissions From Animal Feeding Operations Conference.

The proceedings, "Mitigating Air Emissions from Animal Feeding Operations", with expanded versions of these summaries can be purchased through the Midwest Plan Service.

This Technology is Applicable To:

Species: Poultry, Dairy, Beef, Swine
Use Area: Manure Storage
Technology Category: Manure Treatment (Anaerobic Digestion)
Air Mitigated Pollutants: Odors, Methane, Hydrogen Sulfide

System Summary

Anaerobic digestion of manure provides significant odor control as well as greenhouse gas reductions compared to conventional open manure storage systems. Anaerobic digesters and covered anaerobic lagoons are designed to promote the production of methane and collect the methane and other gases as biogas for utilization. Biogas can be flared or utilized as a fuel for boilers, reciprocation piston internal combustion engines or microturbines. While flaring the biogas does not generate energy, it still provides effective odor control and greenhouse gas reduction when compared to conventional open manure storage emissions. The use of biogas as a fuel results in the production of renewable energy.

Applicability and Mitigating Mechanism

• Works with liquid manure slurries
• Air emissions from digester are combusted with biogas
• Odor is destroyed when biogas is combusted
• Biogas can be used as an energy source

Limitations

• Significant capital expenditure required
• System cost may exceed economic return
• Air pollution controls may be required on biogas combustion devices.
• Biogas (methane) is explosive when mixed in air (LEL from 5 – 15% CH4 in Air)

Cost

An economic analysis of 38 AD system installations is provided in the NRCS Technical Note; An Analysis of Energy Production Costs from Manure Anaerobic Digestion Systems on U.S. Livestock Production Facilities (USDA, 2007). The analysis reports, based on cost data available for specific AD systems, that the capital cost adjusted to 2006 dollars for a covered lagoon AD system ranged from $88,000 to $162,000 and for a plug flow AD system cost ranged from $69,000 to $603,000. The majority of the systems included in the analysis (19 of 38) were dairy plug flow AD systems. The average cost for the dairy plug flow systems included was $748 per cow in 2006 dollars. These costs do not include an estimate for operation and maintenance costs, which was calculated as ranging from approximately 2-7% of the total capitol costs of the digester and generator set. Furthermore, the analysis concludes that approximately 36 percent of the total capital cost is associated with electrical generation equipment.

Authors

Kelsi Bracmort¹, Robert Burns^{2 1}USDA Natural Resources Conservation Service, ² Iowa State University
Point of Contact:
Dr. Kelsi S. Bracmort, kelsi.bracmort@wdc.usda.gov

The information provided here was developed for the conference Mitigating Air Emissions From Animal Feeding Operations Conference held in May 2008. To obtain updates, readers are encouraged to contact the author.