The present invention relates to the field of thermoplastics, the synthesis thereof and the use thereof. It describes in particular the integration of light ash resulting from the combustion of waste from the paper-making industry into thermoplastic matrices. It describes in particular the manufacture and use of novel thermoplastic composite materials containing a thermoplastic resin and light ash resulting from the combustion of waste from the paper-making industry. The present invention also describes a novel filler material capable of being combines with a thermoplastic resin in the manufacture of a thermoplastic composite material.