Step 1: Biomass gasification converts solid biomass into producer gas.
Step 2: Different gasifiers are used depending on type, size, moisture content, and quality of biomass.
Step 3: A fluidized bed gasifier provides good mixing between biomass particles and gasifying medium.
Step 4: Due to better mixing and heat transfer, it can handle different types of biomass materials.
Step 5: Therefore, it is considered versatile and suitable for biomass including sewage sludge and pulping effluents.
\[
\boxed{\text{Fluidized bed gasifier}}
\]