Oxy-fuel combustion is a GHG abatement technology in which coal is burned using a mixture of oxygen and recycled flue gas to obtain a rich stream of CO2 ready for sequestration. A thermobalance and an entrained flow reactor (EFR) were used in this work to study the combustibility of coals and blends with biomass under oxy-fuel conditions. Mixtures of CO2/O2 of different concentrations were used and compared with air as reference. Combustion profiles were performed in the thermobalance and burnout temperatures were calculated from these results. During these tests, it was observed that CO2 concentration exerts a low effect on the combustibility of the samples. In addition, interactions between coal and biomass were negligible. In the EFR tests it was observed that the burnout of coals and blends with a mixture of 79%CO2-21%O2 was lower than in air. However, an improvement in the burnout was achieved when the oxygen concentration was higher than 30%. The results of this work indicate that coal burnout can be improved by blending biomass with coals under CO2/O2 mixtures.Spanish MEC (Ministerio de Educación y Ciencia), Project: “Procesos avanzados de generación, captura y almacenamiento de CO2. Oxicombustión”). CSIC, I3P Program co-financed by the European Social Fund.Peer reviewed