A method of treating an offgas includes purifying the offgas to remove particulate matter, water, undesirable gaseous components and inert gases to produce a dried carbon oxide gas feedstock, and converting at least a portion of carbon oxides in the dried carbon oxide gas feedstock into solid carbon. In other embodiments, a method includes passing a dried carbon oxide gas feedstock through a multi-stage catalytic converter. A first stage is configured to catalyze methane-reforming reactions to convert methane into carbon dioxide, carbon monoxide and hydrogen with residual methane. A second stage is configured to catalyze the Bosch reaction and convert carbon oxides and hydrogen to solid carbon and water.

The present invention relates to a method for efficiently recovering valuable metals from end-of-life waste lithium batteries by dry molten smelting and, more particularly, to a method for recovering lithium by mixing ground or crushed waste lithium batteries with a flux including a Ca compound and a sulfur component and melting same at a high temperature of 1300 C. or higher, and then obtaining a lithium-sulfide compound (Li2SO4) volatilizing therefrom.