Gasification of rice wastes toward green and sustainable energy production: A review

Rice wastes are one of the high potential biomasses due to their large capacity and distribution throughout the world. Harvesting the energy from those rice wastes, including rice husk and straw, is considered clean, sustainable, and economical. Among various energy conversion technologies, gasification is considered a promising technology to convert those wastes to highly-efficient fuel gases. However, the updated technologies in rice waste gasification are still minorly and incomprehensively discussed. This review critically discusses the updated status of gasification technologies, including fixed bed, fluidized bed, entrained bed, and staged gasification, for rice husk and straw, as well as economic analysis. As a matter of fact, rice straw gasification is less studied extensively than rice husk. It is clear that gasification is a promising technology to harvest energy from rice wastes, but it seems that each gasification technology shows its own advantages and disadvantages. Fluidized and entrained beds have higher feasibility compared to fixed bed in terms of cleaner syngas due to lower tar content, leading to simpler cleaning and purification system. Moreover, a staged gasification can potentially offer the best syngas production due to the separation of the processes and process optimization at different levels. From an economic point of view, an integrated rice mill and rice waste gasification is the best option to obtain high economic performance. The utilization of rice wastes, especially through gasification, should be further extended following the trend of a new energy system that is carbon-free. Their utilization for electricity or hydrogen-based fuel production is considered promising to extend the possible market in the future.