This article explains the basics of black liquor gasification in the pulp and paper industry. Black liquor, which accounts for most of the fuel consumed in Kraft mills, is usually combusted in recovery boilers to recover chemicals and to produce process steam and on-site electricity (via a steam turbine). The efficiency of such boilers is, however, low (around 65%-70%). Black liquor gasification is a process in which a clean synthesis gas (syngas) is produced from black liquor by converting its biomass content into a gaseous energy carrier.