Poly(lactic acid) (PLA) is one of the most promising renewable polymer to be employed in injection molded parts. However, the heat deflection temperature and the impact properties should be improved. The reactive blending with polycarbonate (PC) in the presence of an interchange reactions catalyst was demonstrated to be a successful strategy. This process was applied to both virgin and recycled-PC/PLA blends and interesting differences were evidenced as a function of different viscosity in the melt, of the polymers. The blends were prepared in a laboratory extruder, tensile and impact properties were measured, and the phase morphology was investigated even by electron microscopy. Cellulose/polymer composites were also prepared by using PLA/PC blends as polymeric matrix. Fibres having different thickness and aspect ratio were selected and used as fillers in extrusion trials. The elastic modulus increased thanks to the reinforcing behavior of the fibres and several models were applied to fit the experimental trends as a function of composition. Keywords: poly(lactic acid), polycarbonate, recycling, renewable, catalyst