Plastics including polyethylene (PE), polypropylene (PP) and polystyrene (PS) were provided by Li Ke Polymer Materials Company in Shanghai, China. The particle size of plastics is around 80–120 mesh. The black-liquor lignin was grounded and seized to produce particle size of 70–100 mesh. The ultimate analysis and proximate analysis of black-liquor lignin and different plastics are listed in Table 1.