NOVELTY - The method comprises introducing a starting material comprising carbon dioxide gas as a carbon source and hydrogen gas in a reactor, passing the starting material through a reaction section of the reactor, where the reaction section is partially equipped with a catalyst to synthesize a methanol-containing liquid (108), providing the methanol-containing liquid to an output end of the reactor, where the methanol-containing liquid is a mixture of methanol and water, and inserting the methanol-containing liquid in a denitrification process to remove nitrogen content from waste water.    USE - The method for providing and inserting a methanol-containing liquid into a sewage treatment plant for producing methanol (claimed).    ADVANTAGE - The method ensures easy insertion of the methanol-containing liquid into the sewage treatment plant thus allowing easy, energy efficient, economical and rapid production of the concentrated methanol in an environmentally friendly manner with high quality and stability.    DETAILED DESCRIPTION - The method comprises introducing a starting material comprising carbon dioxide gas as a carbon source and hydrogen gas in a reactor, passing the starting material through a reaction section of the reactor, where the reaction section is partially equipped with a catalyst to synthesize a methanol-containing liquid (108), providing the methanol-containing liquid to an output end of the reactor, where the methanol-containing liquid is a mixture of methanol and water, and inserting the methanol-containing liquid in a denitrification process to remove nitrogen content from waste water. The current generator is provided with methane gas and carbon dioxide gas to provide power and flue gas. The current in the reactor is used to produce the methanol-containing liquid. The carbon dioxide gas is deposited to supply the carbon dioxide gas to the reactor, where waste heat in the reactor is used to assist another process in sewage treatment plants. INDEPENDENT CLAIMS are included for:    (1) an apparatus such as silicon-fire system for providing and inserting a methanol-containing liquid; and    (2) a sewage treatment plant with a digester gas.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a wastewater treatment process.    Methanol-containing liquid (108)    Denitrification tank (601)    Silicon-fire systems. (800)