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Anaerobic Digestion 101

For an illustration of a manure-fed anaerobic digester system, see AgSTAR's Anaerobic Digester System Flow Diagram (PDF) (1 pg, 826K), and for more in-depth information on how anaerobic digester systems work see Recovering Value from Waste (PDF) (4 pp, 855K).

Biogas Recovery Systems

Biogas recovery system components:

  • Manure collection systems.
    A system is needed to collect manure and transport it to the digester. Existing liquid/slurry manure management systems can readily be adapted to deliver manure to the anaerobic digester.

  • Anaerobic digesters.
    Anaerobic digesters, commonly in the form of covered lagoons or tanks, are designed to stabilize manure and optimize the production of methane. A facility for digester effluent storage is also required.

  • Biogas handling systems.
    Biogas (a product of the decomposition of the manure, typically comprising about 60 percent methane and 40 percent carbon dioxide) is collected, treated, and piped to a gas use device.

  • Gas use devices.
    Biogas can be used to generate electricity, as a boiler fuel for space or water heating, upgraded to natural gas pipeline quality, or for a variety of other uses. Flares are also installed to destroy extra gas and as a back-up mechanism for the primary gas use device.

  • Digester byproducts.
    In addition to the biogas recovery system, the effluent of the anaerobic digestion can be used to create a number of digester byproducts.
Manure source and collection
Manure handling
Anerobic digester Effluent storage Digester byproducts
Biogas handling systemFlare gas
Gas use

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