Plasma Treatment of Cellulose as the First Step in the Synthesis of Second-Generation Biofuel.

Cellulosic ethanol has been an attractive biofuel for over a century. Despite the large scientific interest, the first step of treating cellulose before enzymatic hydrolysis is still inadequate, so the scientific community seeks innovative solutions. Among them, plasma treatment of raw cellulose represents an interesting approach. The literature on approaches to treat cellulose with gaseous plasma is surveyed, and the results reported by different authors are interpreted. Reactive gaseous particles like ions, electrons, metastables, and radicals interact chemically with the surface but do not cause significant depolymerization of bulk cellulose. Such depolymerization results from bond scission in the bulk cellulose by energetic plasma species capable of penetrating deep into the cellulose. Among them, photons in the range of vacuum ultraviolet radiation (photon energy above the threshold for bond scission) are the most suitable plasma species for the depolymerization of cellulose and the formation of water-soluble fragments, which are suitable for further treatment by enzymatic hydrolysis.