Progress in solid fuel utilization in fuel cells relies on devising effective delivery mechanisms for solid fuel and oxygen to the electrochemical reaction site. This paper provides a mechanistic overview of the different delivery modes and vehicles that have been adopted for engaging solid fuel and oxygen at the electrochemical interface to achieve efficient oxidation of carbon. Also, a "CO shuttle" mechanism is proposed to explain the operation and behavior of several direct carbon fuel cell (DCFC) approaches in CO2 or inert environments. This paper also introduces the operating principle and experimental results of a concept: the fluidized bed (FB) DCFC. It consists of a solid oxide fuel cell arrangement coupled to a Boudouard-type FB dry gasifier. A maximum power density of 175 mW/cm(2) (or 4 W) was achieved at 850 degrees C for the conversion of activated carbon in this FB-DCFC arrangement.