Anaerobic digester 1 Anaerobic digestion 1 Anaerobic treatments Biogas 1 COD removal efficiency 1 Clean development mechanism 1 Effluent treatment 1 Effluents 1 Emission control 1 Energy policy 1 Fatty acids 1 Methane 1 Methane gas 1 Methanosaeta concilii 1 Methanosarcina 1 Methanosarcina sp 1 Operation period 1 Organic loading rates 1 Palm oil mill effluent 1 Palm oil mill effluents 1 Recycling 1 Recycling rate 1 Removal 1 Renewable energies 1 Renewable energy resources 1 Settling tanks 1 Sludge samples 1 Start-up 1 Treatment performance 1 Treatment process 1