Method for obtaining reinforced packaging paper

A procedure for obtaining a reinforced packaging paper comprising:

• a) applying a residual liquor obtained from alcohol-water pretreatment of lignocellulosic residues on a packaging paper, wherein said residual liquor comprises:
• a solid fraction in suspension of 1-70% by weight/volume with respect to the total, comprising lignin and lignin-carbohydrate complexes and no sulphur degradation compounds;
• and
• a liquid fraction of 30-99% by weight/volume with respect to the total, containing glucose between 0.04 and 2.07 g/L, xylose between 0.31 and 14.57 g/L, arabinose between 0.09 and 3.46 g/L, acetic acid between 0.083 and 12.40 g/L, furfural between 0.004 and 8.73 g/L and
• b) drying the packaging paper obtained in step a), to obtain the reinforced packaging paper;
• wherein, prior to step a), the pretreatment of lignocellulosic residues comprises the steps of:
• (i) pretreating the lignocellulosic residues in a mixture of alcohol and water in the presence of an acid that acts as a catalyst to obtain a liquor and the solid pre-treated residues;
• (ii) separating the liquor of (i) from the solid pre-treated residues;
• and
• (iii) concentrating the liquor of (ii) to recover the alcohol and to obtain the residual liquor applied in step a).