The microwave-assisted methane decomposition over a pyrolysis residue of sewage sludge (PRSS), which acted as a microwave receptor and a low-cost catalyst without further activation, was investigated in a multimode microwave reactor. For comparison purpose, methane conversion (MC) over an activated carbon (AC) was also studied. The results indicate that PRSS is a better microwave receptor than AC. Under the same microwave power (MWP), MC over PRSS is markedly higher than that over AC, due to the remarkably higher Microwave heating (MWH) performance of PRSS. MWH of PASS and AC is heavily influenced by atmosphere. Under the same MWP, the stable temperatures of the catalysts in hydrogen, nitrogen and methane atmosphere follow the sequence: T-nitrogen, > T-hydrogen > T-methane. On the other hand, it was observed that nitrogen showed different effect on MC over PRSS and AC under MWH. Specifically, under the microwave-assisted methane decomposition reactions, the effect of nitrogen on MC over PRSS is not obvious, but it has remarkable effect on MC over AC. Additionally, a large number of molten beads were formed on the surface of the used PRSS by microwave irradiation. The composition and formation mechanism of the molten beads were also reported. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.