The invention relates to a composite material filament having rheological characteristics suitable for use in additive manufacturing by extrusion, a method for manufacturing a three-dimensional composite product with an additive manufacturing system from a filament of such composite material, and to a three-dimensional composite product obtained by an additive manufacturing system using such composite material. The filament is formed of material comprising semi-crystalline polylactic acid and chemical pulp of wood-based cellulose fibers, wherein the amount of chemical pulp of wood-based cellulose fibers is selected such that sufficient complex viscosity is obtained at melt state, such that upon additive manufacturing by extrusion, composite melt formed of the filament has a ratio of shear storage modulus to shear loss modulus G′/G″ equal to or higher than 1.0 at a temperature equal to or higher than 133° C.