Supercritical water gasification of sewage sludge by continuous flow tubular reactor: A pilot scale study

•The pilot scale, continuous flow tubular reactor was designed, specially produced.•Effects of temperature, feed concentration, and KOH catalyst were studied.•Temperature, sludge concentration and KOH had great effect on the system yield.•SCWG is a promising and efficient technology for the gasification of wet biomass.•Unlike conventional gasification methods, no hazardous emissions.