The SEM image of milled raw MG (Not shown) shows a highly
fibrillar structure covered by thin waxy layer on its surface, which
is frequently found in herbaceous biomass (Hu and Wen, 2008). In
comparison to the SEM image of untreated raw switchgrass, milled
MG possesses a more ordered structure with less waxy film. After
treating the grass in dilute alkaline, the crystalline structure of MG
fibrils is noticeably disrupted. The waxy layer on the surface is partially
removed, which indicates the breaking down of the lignin
(Hu and Wen, 2008).