In recent times, there has been a growing demand for the use of biomass as an alternative energy due to its sustainable nature. At present, anaerobic digestion and gasification has been proven as a promising technology for exploiting this energy from biomass. This review aims to provide a comprehensive and detailed analysis of the combination of anaerobic and gasification technology as a hybrid system for sustainable waste-to-energy generation. This review reveals that both anaerobic digestion and biomass gasification have been successfully demonstrated as technologies for energy recovery. However, to improve the conversion efficiency in both technologies, the utilization of an intensifier, additive, and enhancer will be required. Moreover, temperature has been identified as a major factor affecting the technologies and should be considered. The bibliometric study conducted revealed that China is the leading country and has set the pace for other countries to follow suit. Subsequently, waste-to-energy research could be easily implemented on a global scale. This study recommends an experimental study of anaerobic digestion and gasification as a hybrid system.