The process energy efficiency of supercritical water gasification was determined by a detailed calculation of the energy balance. Ten tons (wet) per day of chicken manure, the moisture content of which was adjusted, was employed as the model feedstock. An efficiency ratio of 70% was obtained for chicken manure having a water content of 80%. The key operating parameters for ensuring high process energy efficiency were the heating value of feedstock and heat recovery efficiency. This result, along with the heat exchanger efficiency measured in the pilot plant, clearly indicates the high potential of supercritical water gasification technology as a wet biomass gasification process.