A method for manufacturing a composite product comprising organic natural fiber material and matrix material, wherein the lignin content of the organic natural fiber material is under 1 wt. %, and wherein the method comprises: - mixing the organic natural fiber material with the matrix material in a primary mixing stage to form a mixture, the primary mixing stage comprising a contacting step in which - the calculated bulk density of the organic natural fiber material contacted with the matrix material before the contacting step of the primary mixing stage is under 300 kg/m 3, while the contacting step does not start until the matrix material at least starts to melt, i.e. at least 10 wt.% of the matrix material is in melt form, the calculated bulk density referring to the bulk density of the organic fiber material comprising also compressed and decompressed bulk densities, and being determined according to the equation ρ calculated = mass flow of fibre conveying volumetric flow of mixer, - during the contacting step, the organic natural fiber material comes in contact with the matrix material that is at least partly in a form of melt, and - compression ratio of the organic natural fiber material is less than 4, wherein compression ratio is determined according to the equation R = ρ calculated ρ wherein R is compression ratio, ρ calculated is calculated bulk density of the organic natural fiber material, and ρ is apparent bulk density of the organic natural fiber material, the apparent bulk density referring to the bulk density of the organic natural fiber material neither compressed nor decompressed, and being determined by dividing the weight of a sample of the organic natural fiber material by its volume according to ISO 697 and ISO 60 (valid 2011), the method further comprising: - forming a composite product comprising the mixture. - mixing the organic natural fiber material with the matrix material in a primary mixing stage to form a mixture, the primary mixing stage comprising a contacting step in which - the calculated bulk density of the organic natural fiber material contacted with the matrix material before the contacting step of the primary mixing stage is under 300 kg/m 3, while the contacting step does not start until the matrix material at least starts to melt, i.e. at least 10 wt.% of the matrix material is in melt form, the calculated bulk density referring to the bulk density of the organic fiber material comprising also compressed and decompressed bulk densities, and being determined according to the equation ρ calculated = mass flow of fibre conveying volumetric flow of mixer, - during the contacting step, the organic natural fiber material comes in contact with the matrix material that is at least partly in a form of melt, and - compression ratio of the organic natural fiber material is less than 4, wherein compression ratio is determined according to the equation R = ρ calculated ρ wherein R is compression ratio, ρ calculated is calculated bulk density of the organic natural fiber material, and ρ is apparent bulk density of the organic natural fiber material, the apparent bulk density referring to the bulk density of the organic natural fiber material neither compressed nor decompressed, and being determined by dividing the weight of a sample of the organic natural fiber material by its volume according to ISO 697 and ISO 60 (valid 2011), - the calculated bulk density of the organic natural fiber material contacted with the matrix material before the contacting step of the primary mixing stage is under 300 kg/m 3, while the contacting step does not start until the matrix material at least starts to melt, i.e. at least 10 wt.% of the matrix material is in melt form, the calculated bulk density referring to the bulk density of the organic fiber material comprising also compressed and decompressed bulk densities, and being determined according to the equation ρ calculated = mass flow of fibre conveying volumetric flow of mixer, - during the contacting step, the organic natural fiber material comes in contact with the matrix material that is at least partly in a form of melt, and - compression ratio of the organic natural fiber material is less than 4, wherein compression ratio is determined according to the equation R = ρ calculated ρ wherein R is compression ratio, ρ calculated is calculated bulk density of the organic natural fiber material, and ρ is apparent bulk density of the organic natural fiber material, the apparent bulk density referring to the bulk density of the organic natural fiber material neither compressed nor decompressed, and being determined by dividing the weight of a sample of the organic natural fiber material by its volume according to ISO 697 and ISO 60 (valid 2011), - forming a composite product comprising the mixture.