A method for performing an energy efficient desulphurization and decarbonization of a flue gas comprising sulphur oxides and carbon dioxide includes (a) starting a reaction between an electropositive metal and the sulphur oxides and the carbon dioxide of said flue gas; (b) reducing the sulphur oxides and the carbon dioxide of said flue gas simultaneously in an exothermic reaction with an electropositive metal and thereby generating reduced gaseous carbon products and solid reaction products while cooling; (c) extracting the solid reaction products of the reducing step (a) in a solvent to generate a first suspension comprising suspended carbon containing reaction products and sulphur containing reaction products; (d) oxidizing the first suspension obtained in step (b) to generate a second suspension comprising suspended carbon containing reaction products and oxidized sulphur containing reaction products; and (e) separating the oxidized sulphur containing reaction products from the suspended carbon containing reaction products.