The heat source for the endothermic gasification process of almost all pilot plants usually comes from exothermic oxidation, which is called autothermal gasification. However, 2 pilot plants designed their gasification technology to operate in allothermal gasification, where the heat source comes from external sources. The heat source for the gasification reaction of plant No. 4 was the exothermic oxidation reactionin the separate reactor, and plant No. 6 used plasma torch as the heat source, which can provide a very high gasification temperature of 1,000-1,100 °C. Air was the dominant gasification agent used in all pilot plants. Only plant No. 1 used steam-air mixture as the gasification agent to enhance the producer gas heating value.