NOVELTY - The mixed-mode sandwich gasification process, comprises providing a gasifier having two different gasification medium injection zones, providing two different gasification medium, and controlling a volume and temperature of the two separate medium independently such that the gasifier has a reduction zone between two oxidation zones, and using char instead of increasing a fuel conversion and syngas production rate. The gasifier has an evaporation and devolatilization zone adjacent to one of the two oxidation zones. The two oxidation zones are coupled on opposite sides of the reduction zone.    USE - The mixed-mode gasification process is useful for high efficiency conversion of carbonaceous fuels (claimed) to clean syngas with zero residual carbon discharge, where the carbonaceous fuel is useful for commercial applications such as production of heat, electricity, gaseous as well as liquid fuels and chemicals.    ADVANTAGE - The gasification process can be operated at a lower temperature and higher efficiency than standard processes, maximizes the gasification efficiency and flexibility of the conversion process, and is capable of rapidly, economically and completely converting the carbonaceous fuels in an environmentally friendly manner with high quality.    DETAILED DESCRIPTION - The mixed-mode sandwich gasification process, comprises providing a gasifier having two different gasification medium injection zones, providing two different gasification medium, and controlling a volume and temperature of the two separate medium independently such that the gasifier has a reduction zone between two oxidation zones, and using char instead of increasing a fuel conversion and syngas production rate. The gasifier has an evaporation and devolatilization zone adjacent to one of the two oxidation zones. The two oxidation zones are coupled on opposite sides of the reduction zone. One of the two oxidation zones is a char oxidation zone that increases a high-temperature zone for achieving near-equilibrium gas composition and is located downstream of the reduction zone. One of the gasification medium consists of air, oxygen-enriched air and steam, and pure oxygen plus steam, and is injected into the char oxidation zone. Molten ash is recovered downstream of the char oxidation zone. The evaporation and devolatilization zone is located upstream of the two oxidation zones.