Cow-powered Farm: Exploring the Possibilities of Anaerobic Digesters (E3080)

Anaerobic digestion is the biological conversion of organic matter to biogas and digestate in an atmosphere without oxygen.

Cow-powered Farm: Exploring the Possibilities of Anaerobic Digesters (E3080)

What is anaerobic digestion?

Anaerobic digestion is the biological conversion of organic matter to biogas and digestate in an atmosphere without oxygen. Biogas is typically 60 percent methane and 40 percent carbon dioxide, with some trace amounts of hydrogen sulfide and other gases.

Manure characteristics and handling systems for various types of digesters

Anaerobic digesters are sealed (airtight) tanks operated at either a mesophilic (95 degrees to 105 degrees F) or thermophilic (135 degrees to 145 degrees F) temperature. Common types of anaerobic digesters are covered lagoon, plug flow and complete mix. Less common digester types include fixed film, induced blanket and two-phase. Manure characteristics, handling and the use of bedding dictate which technology is appropriate (see Table 1). Depending on the digester type and technology provider, manure may be mixed. Manure and other feedstocks remain in the digester tank for as few as 5 days or as long as 20+ days. Because of Michigan’s cold winters, all digesters constructed in Michigan require insulation and heating to maintain optimum performance throughout the year.

 

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