A method is provided for producing GeCl4 with or without SiCl4 from optical fibers, the method comprises the steps of: reacting comminuted optical fibers including germanium and optionally silicon oxides with a reagent including a solid carbonaceous reducing agent, chlorine and a boron compound to obtain a gaseous product including gaseous GeCl4, gaseous SiCl4, and gaseous BCl3 in accordance with the reactions: 2BCl3(g) + 1.5GeO2 = 1.5GeCl4(g) + B2O3; 2BCl3(g) + 1.5 SiO2 = 1.5 SiCl4(g) + B2O; B2O3 + 1.5C + 3Cl2 = 2BCl3(g) + 1.5CO2; and then condensing the gaseous GeCl4, BCl3 and optionally SiCl4 into liquid GeCl4, BCl3 and optionally SiCl4. The invention further provides a method for producing SiCl4 (and optionally GeCl4) from glassy residues obtained from optical fiber manufacturing and wasted optical cables. The method includes the steps of: reacting comminuted glassy residues with a reagent including a solid carbonaceous reducing agent, a salt, a boron compound to obtain a gaseous product including SiCl4, BCl3, and optionally GeCl4; and then condensing the gaseous SiCl4, BCl3 (with or without GeCl4) into liquid SiCl4, BCl3 and GeCl4. There is also provided a method for producing SiCl4 from a SiO2 containing material.