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.