Pretreatment of the biomass feedstock is the first step in the gasification process. It is essential in some cases due to the process characteristics, but it generally helps to improve the quality of the fuel by homogenizing its size, moisture content, and density. For the operation of continuous processes, biomass storage is required, yet it may lead to issues related to decomposition and self-heating. Pretreatment can help solve or minimize the impact of these issues. It includes several processes, such as size reduction (milling, grinding, and pulverization), screening, drying, torrefaction, pelletization, and pyrolysis.