Method for producing methionine

A method for producing methionine comprising

• a) a crystallization step in which carbon dioxide is introduced into a reaction solution containing an alkali metal salt of methionine, which is obtained by hydrolyzing 5-[2-(methylthio)ethyl] imidazolidine-2,4-dione in the presence of an alkali compound selected from the group consisting of potassium hydroxide, sodium hydroxide, potassium carbonate, and potassium hydrogencarbonate, to precipitate methionine,
• b) a step of subjecting the reaction solution containing precipitated methionine resulting in the crystallization step to a solid-liquid separation to obtain methionine and mother liquor,
• c) a step of recovering methionine from the mother liquor by filtration,
• d) a step of drying the methionine obtained by step c) to obtain dried methionine, wherein the drying step also produces an exhaust,
• e) a step of sieving the dried methionine to obtain sieved methionine,
• f) a step of packaging the sieved methionine powders to obtain a packaged methionine product, and
• g) a step of transporting methionine between each of the steps c) to f),
• wherein the method comprises a step of adding waste methionine to the reaction solution, wherein the waste methionine supplied to the hydrolysis reaction solution includes
• recovered methionine in step c), and
• at least one recovered methionine selected from the group consisting of
• methionine discharged out of the system due to exhaust in the drying step,
• fine powdered methionine passed through a sieve mesh in the sieving step,
• methionine that is soared when filling a container with methionine in the product packaging step, and
• methionine lost during any of the transporting steps.