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Kraft black Liquor: from a Paper Industry’s by-product towards Energy Storage

As stated in the introduction, kraft black liquor is a waste product from paper production using the so-called "kraft" method, developed by Carl F. Dahl in 1879. The name comes from the German kraft, meaning "strength", as the paper resulting from this process was more resistant. It differed from other methods used until then in that it used bases, typically sodium hydroxide (NaOH) and sodium hemi-sulfide (Na ₂ S), to enable the extraction of the cellulose contained in the wood as well as other biopolymers present, namely lignin and hemicellulose. The extracted cellulose then forms the pulp, with the remainder being dissolved and degraded in the form of oligomers, ultimately making up the kraft black liquor. Black liquor is simply an aqueous, alkaline suspension of degraded lignin and hemicellulose, accompanied by the various salts involved in...