To determine the Klason lignin content and sugar concentration, to 250 mg of the solid (dried and extracted white birch or solid after white birch pre-treatment in dioxane/HCl/HCOOH) was added 3.75 mL of a 72 wt% H2SO4 at room temperature. The suspension was stirred periodically (every 15 min with a glass rod) for 2 h and 145 mL of Milli-Q H2O was added followed by refluxing the suspension at 120 °C for 4 h. The suspension was filtered on a tared frit. The solid was dried at 105 °C overnight and the mass of the filtered solid was determined gravimetrically to determine Klason Lignin content. The filtrate was diluted with H2O to 250 mL and concentrated to 50 mL at 80 °C. The solution was then analysed by HPLC to determine the sugar content (glucose, xylose, mannose, galactose and arabinose).