In biomethanation systems ammonia is generated by denitrifying process. However it immediately gets converted into soluble ammonium salts in the presence of acids formed in the acidogenic phase. For raw materials like animal wastes and protein material, amount of nitrogen coming from raw material in the form of proteins is more. The correct and relevant measure of nitrogen is C/N ratio. For stabilized biomethanation, ideal ratio is between 20 to 30 If C/N ratio is low, more free ammonia is produced and the reaction gets affected due to ammonium toxicity. High ammonia generation raises the pH to 8.5 . The pH of the reactor is maintained at around 7.2. Thus ammonia toxicity is true for systems based on human/animal wastes which have C/N ratio less than 20. ( In such systems C/N balance is maintained by adding organic material like straw.) The sludge however can have some ammonium smell, if left as it is. If the sludge is subjected to well designed composting system keeping proper balance of C/N ratio, even this nuisance can be avoided. Digestion List Archives: http://www.crest.org/discussion/digestion/200202/ Digestion List Moderator: Paul Harris, paul.harris@adelaide.edu.au http://www.roseworthy.adelaide.edu.au/~pharris List-Post: <mailto:digestion@crest.org> List-Help: <mailto:digestion-help@crest.org> List-Unsubscribe: <mailto:digestion-unsubscribe@crest.org> List-Subscribe: <mailto:digestion-subscribe@crest.org> Other Digestion Events and Information: http://www.bioenergy2002.org http://crest.org/discussiongroups/resources/biomass/biogas/BIOGASMK.pdf http://www.crest.org/articles/static/1/1010424940_7.html Beginners Tour of Biogas http://WWW.roseworthy.adelaide.edu.au/~pharris/biogas/beginners
