In Fig. 4 the effect of ultrasound amplitude and reaction
time on the methane content is displayed. In most instances
the methane content could be increased by acoustic cavitation
in comparison to the untreated sample. Best results could be
reached on the one hand with high amplitudes and low reaction
time and on the other hand with low amplitudes and
long reaction time. As described before, an intense energy
input (once by long reaction times or by higher amplitudes