Methane production from biomass gasification is an alternative route compared to conventional techniques for the efforts to reduce the carbon foot print. In the current work, production of methane is studied from steam gasification of palm kernel shell (PKS) in thermo gravimetric analyser (TGA) and mass spectrometer (MS). Response surface methodology (RSM) is applied to investigate the effect of operating parameters and to identify the optimized parameters. The four main process variables were investigated within the specific range of temperature of 650 -750'C, particle size of 0.5-1 mm, CaO/biomass of 0.5-2 and coal bottom ash of 0.02-1. Temperature and CaO/biomass ratio were found to be the most influencing variables on methane production. The optimised conditions obtained were temperature of 750 °C, particle size of 0.99 mm, CaO/biomass of 1.25 and coal bottom ash of 0.08. The presence of Fe, Mg, Al oxides in the coal bottom ash catalysed the process and enhanced the methane yield from 37 to 43.3 vol . © 2016 The Authors.