A process for preparing methanol by (a) producing a synthesis gas comprising carbon monoxide, carbon dioxide and hydrogen from a carbonaceous feedstock in a synthesis gas production unit, (b) feeding the synthesis gas from stage (a) to a methanol synthesis unit and converting it at a temperature of 150 to 300°C and a pressure of 5 to 10 MPa abs in the presence of a methanol synthesis catalyst to a reaction mixture containing methanol, water, carbon monoxide, carbon dioxide, hydrogen, dimethyl ether and methane, condensing a methanol- and water-enriched crude methanol stream out of said reaction mixture, and conducting the crude methanol stream and a gaseous stream comprising carbon monoxide, carbon dioxide, hydrogen and methane out of the methanol synthesis unit, (c) expanding the crude methanol stream from stage (b) in an expansion unit to a pressure of 0.1 to 2 MPa abs, and obtaining an expansion gas comprising carbon dioxide and methane and a degassed crude methanol stream enriched with methanol and water, (d) separating a carbon dioxide- and dimethyl ether-comprising low boiler stream by distillation from the degassed crude methanol stream from stage (c) in a distillation apparatus, and obtaining a methanol- and water-enriched bottom stream (VIII), and (e) separating a water-containing high boiler stream from the bottom stream (VIII) from stage (d) in a further distillation apparatus, and obtaining methanol by distillation as stream, which comprises (f) feeding the carbon monoxide, carbon dioxide, dimethyl ether and methane components of value in streams and in at least one of the two streams and to a combustion unit and combusting them therein with supply of an oxygenous gas having an oxygen content of 30% to 100% by volume, forming carbon dioxide-containing flue gas, (g) separating a carbon dioxide-enriched stream from the carbon dioxide-containing flue gas from stage (f) in a carbon dioxide recovery unit to form an offgas stream (XIII), and (h) recycling the carbon dioxide-enriched stream separated off in the carbon dioxide recovery unit from stage (g) to the synthesis gas production unit of stage (a) and/or to the methanol synthesis unit of stage (b). (a) producing a synthesis gas comprising carbon monoxide, carbon dioxide and hydrogen from a carbonaceous feedstock in a synthesis gas production unit, (b) feeding the synthesis gas from stage (a) to a methanol synthesis unit and converting it at a temperature of 150 to 300°C and a pressure of 5 to 10 MPa abs in the presence of a methanol synthesis catalyst to a reaction mixture containing methanol, water, carbon monoxide, carbon dioxide, hydrogen, dimethyl ether and methane, condensing a methanol- and water-enriched crude methanol stream out of said reaction mixture, and conducting the crude methanol stream and a gaseous stream comprising carbon monoxide, carbon dioxide, hydrogen and methane out of the methanol synthesis unit, (c) expanding the crude methanol stream from stage (b) in an expansion unit to a pressure of 0.1 to 2 MPa abs, and obtaining an expansion gas comprising carbon dioxide and methane and a degassed crude methanol stream enriched with methanol and water, (d) separating a carbon dioxide- and dimethyl ether-comprising low boiler stream by distillation from the degassed crude methanol stream from stage (c) in a distillation apparatus, and obtaining a methanol- and water-enriched bottom stream (VIII), and (e) separating a water-containing high boiler stream from the bottom stream (VIII) from stage (d) in a further distillation apparatus, and obtaining methanol by distillation as stream, (f) feeding the carbon monoxide, carbon dioxide, dimethyl ether and methane components of value in streams and in at least one of the two streams and to a combustion unit and combusting them therein with supply of an oxygenous gas having an oxygen content of 30% to 100% by volume, forming carbon dioxide-containing flue gas, (g) separating a carbon dioxide-enriched stream from the carbon dioxide-containing flue gas from stage (f) in a carbon dioxide recovery unit to form an offgas stream (XIII), and (h) recycling the carbon dioxide-enriched stream separated off in the carbon dioxide recovery unit from stage (g) to the synthesis gas production unit of stage (a) and/or to the methanol synthesis unit of stage (b).