the sixth day but then increased sharply on the seventh
day to about 7.21 mL. Optimum biogas production was
not attained in this case as there was evidence from the
Figure 3 to suggest further production. Digester C rose
progressively from 0 mL from the start of the experiment
to about 6.72 mL on the fifth day and then decreased the
two remaining days of the study. Optimum gas
production could be said to be attained on the fifth day
since it recorded the highest mean biogas within the time
frame for Digester C.