Fig. 1 shows the images of cogon grass before and after combustion.
Once the organic compounds were decomposed, many empty spaces
were left between the veins. It can be seen in Fig. 1c that ashes are distributed
on the mid-rib and parallel veins of the grass. These ashes
mainly consisted of silica. Because very little ash remained after combustion,
silica content in cogon grass is relatively low. To further confirm
the hypothesis, the composition of major elements in cogon grass was
obtained using CHNS. The results are tabulated in Table