Removal of root extractives

A procedure of the NREL/TP-510-42619 standard has been followed in order to remove extractives from the root samples [66]. In this procedure, the samples have been wrapped in Kimwipes^® and stapled into 2 cm Kimwipes^® square packets. The samples have first been Soxhlet-extracted in water for 15 hours and subsequently air-dried overnight. The air-dried samples have been returned into Soxhlets and extracted in 95% ethanol for 24 hours. The samples have been kept at room temperature for two days to allow for the evaporation of ethanol. Additionally, the samples have then been dried in an oven at 50°C until reaching constant mass (Heratherm ^™ OMS60, Thermo Fisher Scientific ^™). The dry masses of the samples have been recorded before further processing, and samples stored in a desiccator until further processing.