With increasing reaction time and amplitude the energy
input in the reaction system increases, too, leading to a higher
number of cavitation bubbles and therefore to increasedcavitational effects [13]. With amplitude of 125 mm and 2 min
reaction time the biogas yield is depressed (379 NL/kg ODM) in
comparison with the results at the same reaction time and
lower amplitudes. In this case the concentration of the
bioavailable substances is maybe too high, leading to an
acidification in the fermentation tests and therefore to nonideal
milieu for methanogenesis. So, the energy input has to
be investigated in relation to the substrate used and adjusted
to reach optimal conditions for the fermentation process.