Part 2 of Biogas and Anaerobic Digestion

Biogas and Anaerobic Digestion | Covered Lagoon

A covered lagoon digester is a large anaerobic lagoon (not a manure storage pond or basin) with a long retention time and a high dilution factor.  Typically covered lagoons are used with flush manure management systems that discharge manure at 0.5 to 2 percent solids.  The in-ground, earth or lined lagoon is covered with a flexible or floating gas tight cover.  They are not heated and considered ambient temperature digesters.  Retention time is usually 30-45 days or longer depending on lagoon size.

In climates that have elevated year round temperatures, such as southern and western U.S., these digesters can produce stable, reduced odor, nutrient rich effluent for application on fields and crops; pathogen and weed seed reduction and; produce biogas for farm energy use.  Heat recovery from the biogas can be used to heat nurseries on swine farms and warm milking parlors on dairy farms.  Very large lagoons in hot climates may produce sufficient quantity, quality and consistency of gas to justify use in an engine generator.  In areas with cooler climates, waste digestion, odor control and gas production will be less consistent and the low quality gas may need to be flared off much of the year for odor control and greenhouse gas reduction.


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