Biomass can be effectively converted to synthetic natural gas (Bio-SNG) in water near or above its critical point (374°C, 22.1 MPa). If an active and selective catalyst is used, no tars or char are formed. The onset of the gasification reaction was visualized in sealed quartz capillaries as high pressure batch reactors by using a microscope. By pressure differential analysis of batch experiments, the onset temperature was found in the range 250-300°C, which is much lower than conventional atmospheric gasification processes operating at 800-900°C. A supported noble metal catalyst exhibiting excellent long-term stability was tested at 400-500°C and space velocities up to 33 gHC/gcat./h in a continuous test rig at 30 MPa.