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Home > Protecting Our Lands & Waters > Conservation > Conservation Practices > Manure/Methane Digester

Conservation Practices
Minnesota Conservation Funding Guide


Manure/Methane Digester

Plug-flow manure digester. Photo MDA.
Plug-flow manure digester. Photo MDA.

This on-farm methane-powered engine and generator produces energy from the manure in a digester. Photo MDA.
This on-farm methane-powered engine and generator produces energy from the manure in a digester. Photo MDA.

Anaerobic manure digesters (also called methane digesters) collect manure and convert the energy stored in its organic matter into methane, which is used to produce energy (gas or electricity) for on-farm or off-farm use. The conversion to methane is the result of anaerobic digestion—a biochemical process in which organic matter is decomposed by bacteria in the absence of oxygen. Digesters must be airtight (no oxygen) for anaerobic digestion to occur.

Methane is often called biogas; technically, biogas is methane plus other anaerobic digestion byproducts. At any rate, the gas is flared or combusted to generate energy—a process with multiple other benefits including (among others) significantly reduced feedlot odors and greenhouse gas emissions.

Generally, manure used in digesters should have a total solids concentration of 14% or less and be mostly free of soil, sand, stones or fibrous bedding material (it can be processed to remove these materials). Supplemental feedstocks such as food processing wastes and wastewater can often be added to manure digesters.

Why consider an anaerobic digester on your farm?

Environmental benefits

  • Turns manure into a source of renewable energy
  • Improves air quality by reducing odors and greenhouse gas emissions
  • Protects water quality by reducing the potential for pathogens to enter surface or ground water

Practical benefits

  • Generates energy that can be sold
  • Generates heat or other energy for on-farm use
  • May qualify for carbon credit payments
  • Aids manure management by making solid-liquid separation easier
  • Results in potentially higher-quality manure for use on crops (more nutrient-rich and fewer weed seeds)
  • Enables animal bedding to be reused
  • Reduces feedlot problems with flies

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Similar & related practices

More information

Guidance from USDA's Natural Resources Conservation Service

Other resources

MN Dept of Agriculture

    Other

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    Contact

    See contacts for specific programs that fund this practice in the side-by-side payment comparison or contact your local Soil and Water Conservation District