This work presents and applies a camera-based fuel tracking system for quantification of the motion of individual fuel particles at the surface of bubbling fluidized beds operated under hot conditions. In particular a bubbling fluidized bed with a cross section of 1.44 m(2) operated at 800 degrees C is investigated. Mixing of wood pellets and wood chips is investigated by feeding batches of fuel and applying multi particle tracking to the videos recorded by a specially designed camera probe. The influence of the bulk solids cross-flow and fluidization velocity on the mixing of fuel particles is analyzed. It is shown that the new fuel tracking method can withstand industrial conditions. Applying the method gives reproducible results and yields lateral dispersion coefficients in the range 10(-3)-10(-2) m(2)/s for both pellets and wood chips. The lateral mixing of the fuel increases with fluidization velocity and, to a minor extent, with the cross-flow of bulk solids. As observed in previous work, the location of fuel particles on the bed surface confirms the existence of preferred bubble paths, and these are smeared out by the cross-flow of bulk solids. The vertical mixing is hindered by the cross-flow of bulk solids, while it is enhanced by fluidization velocity, which is in agreement with previous research. (C) 2015 Elsevier Ltd. All rights reserved.