AbstractLiquid–solid fluidization characteristics of irregularly shaped Biobone particles were studied in a fluidized bioreactor column 2.35 m high and 0.1 m dia. The wet biobone particles had a density of 1,890 kg/m3. Two size ranges were studied: 1.70–2.36 mm and 1.25–2.36 mm. The Biobone is a natural cheap material composed of collagen, which is a strong protein structure, embedded with microcrystals of hydroxyapatite and calcium phosphate, and it is an excellent matrix of commercial importance used for the immobilization of enzymes, whole cells and other biocatalysts. Fluidization characteristics of Biobone particles, which include measurements of pressure drops, holdups, minimum fluidization velocities, particle entrainment, and residence time distributions at different water superficial velocities, are reported. Because of the highly irregular shape of Biobone particles, new fluidization behavior was observed, which was much different from the fluidization behavior of spherical particles reported in the literature. A new channeling index, Ic, is proposed to quantify the channeling characteristics of fluidized Biobone particles, and a new parameter, α, was developed to distinguish the transition between fixed and fluidized states of the Biobone par