Experimental results show that, depending on processing conditions and material formulation, a single-screw extrusion process based on chemical foaming can lead to a significant reduction in weight of unreinforced PLA foam (up to 48%) and cellulose fibre reinforced PLA foams (up to 25%) as well as an improvement in mechanical properties (tensile strength up to 30%). Nevertheless, it requires an optimized control of all process and material parameters.