bacterial counts before and after pasteurization


Pasteurization is needed, when food or household waste, animal by-products or other off-farm materials come into play. Pasteurization of animal by-products or off-farm materials are commomly operated as a batch process prior to entering the anaerobic digester.  


External products like household or food leftovers need to be heat treated at 158°F or 70C° for minimum 1 hour.


The table on the side gives an idea on the bacterial biomass present in raw manure (Gülle) for some selected bacterial species. It also reveals that mixing of manure and off farm material leads to higher bacterial numbers in the substrate ( going into the digester. Straight after pasteurisation (Hyg.out.) there is no evidence of the indicator organisms monitored. During mesophilc digestion the substrate faces a slight increase in e.g. enterococci.   


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