Artichoke processing wastes were used to evaluate the biogas generation by
anaerobic digestion using semi-continuous feeding system. Obtained data show
that populations of anaerobic saccharolytic, proteolytic, cellulose decomposers
and acid producing bacteria were higher records at 20 days hydraulic retention
time (HRT) than either 30 or 40 days HRTs. Highest concentration of volatile
fatty acids (VFA) was obtained when the HRT and feeding rate were 20 days and
2 liter/day, respectively. The pH values which ranged form 7.17-7.72 were
favourable to biogas generation and methane production and this was observed
at different fermentation periods. The loss percentages in total and volatile solids
were increased with the increase of hydraulic retention time. The highest rates of
biogas production were observed during the first fermentation turn and this was
true at various hydraulic retention times. Average methane percentage was
higher at 20 days HRT compared to the methane percentages those observed at
HRTs of 30 and 40 days. Highest rates of biogas and methane production per kg
volatile solids either added or consumed were observed during the first
fermentation turn. Biogas and methane production rates were higher at 20 days
HRT during the first turn than other HRTs and fermentation turns used dul"ing
the study.