The cost of the pyrolysis reactor amounts to approximately 10-15% of the total plant cost (Huber et al. 2006). However, the reactor is the central part of the process, having a key effect not only on the energy efficiency of the process but also the yields and characteristics of the resulting products. Reactors intended for the fast pyrolysis of biomass need to fulfill three basic requirements: first, very fast heat transfer in order to ensure rapid heating of the biomass particles at relatively low temperatures; second, very low residence time of the vapors inside the reaction chamber in order to minimize secondary reactions; and third, reduced purge gas flow in order to reduce dilution of volatile products and condensation requirements. Other aspects that need to be taken into consideration include attrition of the chars in order to avoid contamination of volatile products, and biomass particle size requirements in order to avoid excessive energy and economic costs in feedstock preparation. Various reviews have been dedicated to describing alternative reactor designs for fast pyrolysis (Meier and Foix, 1999; Bridgewater and Peacocked, 2000; Mohan et al., 2006).