Where Do The Nutrients Go During Anaerobic Digestion?
The eXtension web site addresses the question about whether or not manure nutrients disappear in an anaerobic digester. “Nutrients in an anaerobic digester do not disappear,” says Patrick Topper, Pennsylvania State University. “The reason some people claim that a digester ‘eats’ nutrients is because some of the nutrients settle out in the sludge and stay in the digester until it is mechanically cleaned out.” This process is especially true in Plug Flow digesters. Phosphorus often settles out during the digestion process, for example, thus giving a net reduction in phosphorus. In reality, the phosphorus is being stored in the solids, or sludge, accumulating in the digester. Some of the organic nitrogen may settle and a very small fraction may be lost with the biogas as ammonia, but essentially the nitrogen is not reduced in a digester, according to Topper. Learn more in the Pennsylvania State University fact sheet entitled, “The Fate of Nutrients and Pathogens during Anaerobic Digestion
