Dairy Anaerobic Digestion Systems and their Impact on Greenhouse Gas and Ammonia Emissions

Anaerobic digestion is a process in which microorganisms degrade organic material, such as dairy manure, in the absence of oxygen to produce biogas and digestate. Biogas is composed mostly of methane, which is the main constituent of natural gas (Table 1). Digestate is the degraded organic material that exits the digester after the digestion process. Digestate contains nutrients that can be used as an organic fertilizer. Although many of the nutrients change form, the total amount of nutrients remains nearly constant (<1% of nitrogen is lost in biogas). Anaerobic digestion produces renewable energy while also reducing odors, pathogens, antibiotics, and greenhouse gas emissions.