NITROGEN ENRICHMENT OF ORGANIC WASTES BY AMMONIATION

The benefits of amending soil,vith cellulosic organic wastes generated during the processing of agricultural products are limited by their l ow nutrient value, occasional strong odors, and high costs of transpor tation. The objective of this study was to develop a chemical process to enrich the N content and reduce the water content of cellulosic org anic wastes to enhance their value as nutrient supplements. Various co mbinations of pressure (300-9000 kPa), temperature (60-240 degrees C), and O-2 and NH3 concentrations were used to identify optimal paramete rs for N enrichment of various wastes by reaction with anhydrous NH3. Total N contents of sugarcane (Saccharum officinarum L.) milling waste s, rice (Oryza sativa L.) hulls, and several composts were increased 5 .9 to 17.1 times under the optimal combination of reaction parameters tested. Ammoniation resulted in dry, dark brown. organic products cont aining 50 to 90 g N kg(-1) and having negligible odor. Nitrogen enrich ment increased as the organic C content of the organic wastes increase d. For all materials studied, the optimal N enrichment was obtained at a reactor pressure of 7200 kPa. Optimal reaction temperature varied b etween 80 and 180 degrees C. Maximum fixation was attained in <120 min for all materials studied. Products ammoniated under optimal conditio ns contained 87 to 93% of their N as organic N. Increasing reaction te mperature decreased the proportion of,vater soluble to insoluble organ ic N in ammoniated materials. Anaerobic incubation of soils amended wi th ammoniated bagasse indicated about 20% of N in this material was re leased as mineral N within 14 d.