The anaerobic digestion of kitchen waste was studied in both batch and continuous modes. The effect of increasing loading rates on pollutant removal and biogas production was investigated for single-phase digestion and twophase digestion systems. The anaerobic biodegradability of the kitchen waste obtained from the batch study was 83.5%. Single-stage digestion of kitchen waste was subjected to varying organic loading rates (OLR) ranging from 1.5 kg volatile solids (VS) m-3 d-1 to 5.5 kg VS m-3d _1, with a common, hydraulic retention time (HRT) of 15 d. The optimum performance of the system was observed at an OLR of 4.5 kg VS m -3 d-1 in terms of pollutant removal efficiency and biogas production. The removal rates for chemical oxygen demand (COD) and VS at this optimal OLR were 81% and 79%, respectively. Maximum, production of the methane was 0.288 m3/kg of VS added. Beyond the optimal OLR, the volatile fatty acids concentration increased and reached its maximum value (9.2 g/L) at the higher loading rate tested (5.5 kg VS m3 d-1). Anaerobic digestion of the kitchen waste was earned out in a two-stage reactor with different loading rates of 4, 6, and 8 kg VS m3 d-1. The retention time given to both hydrolysis and methanogenesis phases was 5 d, for a total HRT of 10 d. Best performances were observed in the third run with the OLR of 8 kg VS m-3 d-1. High removal efficiencies for COD and VS were found as 92% and 94%, respectively. A total of 0.22 m3 of methane was produced by 1 kg of VS added. Responses to the fluctuations in the loading rates were sudden and many times unfavourable in the singlestage system, while the fluctuations were suppressed or overcome at a faster rate in. the two-stage reactor, without creating too many problems. Comparison of the overall performance showed that phase-separated digesters or the two-stage digesters may offer the best choice for high efficiency, concerning pollutant removal. © 2008 NRC Canada.