In the present work, effect of micro nutrients (MN) (NiCl2, Fe2O3, CoCl2, (NH4)(6)Mo7O24) was compared with nanoparticles (NPs) of respective MN with cattle manure (CM) slurry in single and bi-phasic anaerobic digestion (AD) at a hydraulic residence time (HRT) of 20 days at a mesophilic temperature of 37 +/- 2 degrees C for the generation of biogas with enhanced methane (70-80%). Experiments were also carried out with CM slurry as control. During single phase AD, highest biogas production of 0.16 L/(g VS reduced) and 0.14 L/(g VS reduced) was obtained from Fe3O4 NPs and CoCl2 MN respectively whereas in bi-phasic AD 0.3 L/(g VS reduced) and 0.2 L/(g VS reduced) was obtained from NiO NPs and NiCl2 MN correspondingly. The results elucidated that NiCl2 (either as MN or NPs) yielded highest biogas in comparison with either control or other MN and NPs. (C) 2017 Elsevier Ltd. All rights reserved.