Method for producing alkali metal cyanides as solids, comprising the steps: i) an absorption step in the form of absorption of hydrogen cyanide from a hydrogen-cyanide-containing synthesis gas in an aqueous alkali metal hydroxide solution to produce an aqueous alkali metal cyanide solution; ii) a preparation step for the cyanide-containing waste gases obtained in step i), wherein iia) in a first combustion step, the cyanide-containing waste gases obtained in step i) are subjected to substoichiometric combustion (oxygen content in the combustion chamber smaller than stoichiometrically required); iib) in a cooling step, the reaction mixture obtained in step iia) is cooled by introducing an aqueous liquid; iic) in a second combustion step, the reaction mixture obtained in step iib) is combusted by supplying further oxygen under superstoichiometric conditions (oxygen content in the combustion chamber greater than stoichiometrically required); iii) a crystallization step in the form of introducing the alkali metal cyanide solution into an evaporative crystallizer which is heated by heating, in particular by steam heating, and in which a pressure below atmospheric pressure (below 1013 mbar) is present; iv) a condensation step for the cyanide-containing vapors produced in step iii) to a cyanide-containing vapor condensate; v) a recirculation step in which the cyanide-containing vapor condensate obtained in step iv) is used as an aqueous liquid in step iib). i) an absorption step in the form of absorption of hydrogen cyanide from a hydrogen-cyanide-containing synthesis gas in an aqueous alkali metal hydroxide solution to produce an aqueous alkali metal cyanide solution; ii) a preparation step for the cyanide-containing waste gases obtained in step i), wherein iia) in a first combustion step, the cyanide-containing waste gases obtained in step i) are subjected to substoichiometric combustion (oxygen content in the combustion chamber smaller than stoichiometrically required); iib) in a cooling step, the reaction mixture obtained in step iia) is cooled by introducing an aqueous liquid; iic) in a second combustion step, the reaction mixture obtained in step iib) is combusted by supplying further oxygen under superstoichiometric conditions (oxygen content in the combustion chamber greater than stoichiometrically required); iia) in a first combustion step, the cyanide-containing waste gases obtained in step i) are subjected to substoichiometric combustion (oxygen content in the combustion chamber smaller than stoichiometrically required); iib) in a cooling step, the reaction mixture obtained in step iia) is cooled by introducing an aqueous liquid; iic) in a second combustion step, the reaction mixture obtained in step iib) is combusted by supplying further oxygen under superstoichiometric conditions (oxygen content in the combustion chamber greater than stoichiometrically required); iii) a crystallization step in the form of introducing the alkali metal cyanide solution into an evaporative crystallizer which is heated by heating, in particular by steam heating, and in which a pressure below atmospheric pressure (below 1013 mbar) is present; iv) a condensation step for the cyanide-containing vapors produced in step iii) to a cyanide-containing vapor condensate; v) a recirculation step in which the cyanide-containing vapor condensate obtained in step iv) is used as an aqueous liquid in step iib).