Ultrasonication was applied to lower the ammonia level in livestock waste to enhance the anaerobic digestion performance. In simulated waste tests, in spite of an identical temperature increase, a higher ammonia removal rate was observed at lower frequency. This could be explained by the existence of athermal effects, accounting for 64% of the total ammonia removal rate. These effects originated from various convections (micro-streaming, micro-convection, shock-waves, and micro-jets), possibly caused by stable bubbles, and this indigenous mixing ability led to a negligible effect of aeration in the ultrasound assisted ammonia stripping process. In actual waste tests, an ammonia removal rate of up to 55% was achieved with a 0.77 h^(-1) mass transfer rate coefficient. After ultrasonication (28 kHz, pH 11, 15 min) of livestock waste, 58% higher CH4 yield was achieved due to the decrease of ammonia concentration (28%) and enhanced solubilization (51%).