NOVELTY - Producing particles of a coal-like solid, comprises reacting an aqueous reaction mixture containing a plastic material, comprising hydrolysable polymers preferably polyurethanes and/or polyesters, and a biological material, at a pressure of 2-60 bar and a temperature of 195-225 degrees C in the presence of a catalyst, preferably an acid, a base and/or a metal-based catalyst or sulfur-based catalyst, obtaining slurry of coal particles of a similar solid, adding an organic solvent to slurry of particles after reduction of water content of particles, and receiving a slurry of particles.    USE - The slurry of particles of coal-like solid is useful: as a carbon black substitute; and as a filler, as a reinforcing filler, as UV stabilizer, conductivity promoters, as a pigment, as a component for the preparation of color compositions, cosmetic compositions, building materials, plastic or rubber product, preferably vehicle tires, rubber mats, wet clothing, rubber mats, rubber sheets, rubber seals and bearings (all claimed).    ADVANTAGE - The method: minimizes the release of carbon dioxide; and utilizes fast growing plant that is easily available.    DETAILED DESCRIPTION - Producing particles of a coal-like solid, comprises reacting an aqueous reaction mixture containing a plastic material, comprising hydrolysable polymers preferably polyurethanes and/or polyesters, and a biological material, at a pressure of 2-60 bar and a temperature of 195-225 degrees C in the presence of a catalyst, preferably an acid, a base and/or a metal-based catalyst or sulfur-based catalyst, over a period of 0.1-48 hours, obtaining slurry of coal particles of a similar solid, adding an organic solvent to the slurry of particles of coal-like solid after reduction of water content of particles, and receiving a slurry of particles or particles with an increased proportion of smaller particles. The weight ratio of plastic material to biological material is 750:1-1.5:1. INDEPENDENT CLAIMS are also included for:    (1) Slurry of particles of the coal-like solid, obtained by the above mentioned without reducing the water content, or particles of a coal-like solid, obtained by reducing the water content of the slurry; and    (2) a carbon black substitute comprising the slurry of particles of coal-like solid.