In integrated gasification combined-cycle (IGCC) systems, the synthetic gas is cleansed of its hydrogen sulfide, ammonia and particulate matter and is burned as fuel in a combustion turbine (much like natural gas is burned in a turbine). The combustion turbine drives an electric generator. Hot air from the combustion turbine is channeled back to the gasifier or the air separation unit, while exhaust heat from the combustion turbine is recovered and used to boil water, creating steam for a steam turbine-generator.

Combined use of combustion turbines and steam turbines are known as "combined cycles", which is why gasification-based power systems can achieve unprecedented power generation efficiencies. Currently, gasification-based systems can operate at around 45% efficiencies. A conventional coal-based boiler plant, by contrast, employs only a steam turbine-generator and is typically limited to 33-38% efficiencies.