The Fe/olivine catalyst effectiveness regarding tar primary reduction during biomass gasification in dual fluidized beds has been investigated. The use of Fe/olivine instead olivine leads to an important decrease in the amount of produced tar, which was reduced by up to 65% at 850 degrees C, naphthalene being the most stable molecule. It has been found that Fe/olivine materials have a double effect on tar destruction. On the one hand, they act as a catalyst for tar and hydrocarbon reforming. On the other hand, they can act as an oxygen carrier that transfers oxygen from the combustor to the gasifier, and part of the oxygen is used to burn volatile compounds. The catalyst was fairly stable because the result was confirmed during 48 h of continuous operation. The Fe/olivine material characterization (X-ray diffraction, Mossbauer spectroscopy, temperature programmed reduction and oxidation, etc.) revealed that the catalyst structure was maintained despite the large number of oxidizing-reducing cycles. The carbon that formed on the catalyst surface was low and easily oxidized in the combustion zone. Therefore, the inexpensive and non-toxic Fe/olivine catalyst is a material suitable for use as primary catalyst in a fluidized bed gasification of biomass. (c) 2012 Elsevier B.V. All rights reserved.