In an experiment with 3.6 % acid content and a similar milling duration as for cellulose a lower soluble fraction was achieved compared to impregnated cellulose (Figure , second bar). This experiment showed that the milling duration has to be increased for the lignocellulosic feedstock, which is probably due to the lignin content that hardens the structure. The results after increasing the milling duration as well as varying the acid content are shown in Figure . Without acid a soluble fraction of around 25 % is obtained. Hereby we have to keep in mind that wheat straw has 14.3 % extractives which are included in the soluble products. Substracting the fraction of extractives from the soluble product fraction leads to an uptake around 10 % which is in the same range as for cellulose alone. For higher milling durations of 255 min and acid contents of 3.6 and 6 %, a soluble fraction above 90 % is achieved. Hereby, sufficient energy was supplied to the system to break the rigid structure and then depolymerize it.