For impregnation the required amount of 96 % sulfuric acid was weighed in a 500 mL round bottom flask and diluted with about 50 mL diethyl ether per 5 g biomass. Here, the acid content is given in % based on the total mass including acid load itself. After adding the biomass the resulting suspension was stirred for 1 h at room temperature. The solvent was removed under reduced pressure and the product was dried under vacuum on the Schlenk line. The grinding balls are placed in the grinding bowl, 5 g of impregnated cellulose is added and the grinding process is started. The experiments carried out were run with grinding cycles of five minutes grinding followed by two minutes cooling, with the aim that temperatures of 90 °C were not exceeded to prevent subsequent reactions. Possible subsequent products starting from monomeric sugars which were formed in small amounts could be furfural and hydroxymethylfurfural. For clarity, only the total effective grinding time without the cooling cycles is given. Directly after the grinding process, the temperature inside the grinding bowl is measured and noted with a Scan Temp Pro 440 infrared thermometer in order to exclude subsequent reactions at temperatures above 90 °C.