After alkali treatment (Fig. 2D and E), it is clear that some cell tissues were destroyed and that the connections between cells are less than in the case of the untreated garlic straw (GS). This fact could indicate the partial removal of the external non-cellulosic layer, composed of materials such as hemicelluloses, lignin, wax, and other impurities contained in the garlic straw. This pre-treatment step was therefore essential to promote swelling of the fiber structure and to enhance the penetration of the bleaching agents.