The cooxidative effect of ethanol on ammonia oxidation in supercritical water was studied for a range of temperatures (655-705 degrees C), initial ammonia (1-3 mM), ethanol (0-1.0 mM), and oxygen concentrations (0.7-5.0 mM), corresponding to fuel equivalence ratios ranging from 0.9 to 2.2 for the complete combustion of both organic species. With a stoichiometric amount of oxygen available for complete oxidation, the addition of ethanol on an equivalent molar basis was found to increase ammonia conversion from 20 to 65% at initial concentrations of I mM for each reactant, T = 700 degrees C, P = 246 bar, and tau = 2.5 s. Nitrous oxide was produced in much larger quantities for ammonia-ethanol cooxidation than for ammonia oxidation. Based on fractional yields of nitrogen product, this amounted to 40-75% for co-oxidation with ethanol versus 4-13% without ethanol present. (c) 2007 American Institute of Chemical Engineers.