**3.4 Rotary drum gasifiers**

To reach uniformity of the biomass during gasification without combustion (using gasifying agents rather than oxygen/air), mechanical mixing can be applied as rotary kiln type reactor (**Figure 6b**). In this rotating cylinder, biomass is well mixed in contact with gasifying agents. Differing from fluidized bed and entrained flow equipment, the gasifying agents' flow rates can be at any value in rotary drum gasifiers.