Decomposition of Four Ammonium Nitrate Propellants

The biodegradability of four ammonium nitrate propellants, trimethylammonium nitrate TMAN, isopropylammonium nitrate IPAN, triethanolammonium nitrate TEAN, and hydroxylammonium nitrate HAN was assessed in batch and continuous cultures under a variety of conditions. IPAN, TMAN, and TEAN were decomposed under aerobic conditions in batch and continuous cultures in a variety of media. Under anaerobic conditions in batch systems and denitrification conditions in continuous flow systems TMAN and TEAN were decomposed while IPAN was incompletely degraded. No significant build-up of intermediates was observed under any of the conditions studied. All three compounds were readily decomposed in soils at a variety of concentrations and in a range of different soil types. HAN was found to be chemically unstable down to a pH of 5.9. All four compounds tested negative in the ames screening test for mutagenicity. The contamination of stock solutions of TMAN and TEAN with nitrosamines may present the biggest hurdle to overcome in looking towards successful biological treatment of these propellants.