a–d SEM micrographs for the cross-sections of the fuel briquettes with the smashed rice straw (b2 mm). (a) test B9 (100% smashed rice straw, at room temperature); (b) test
B13 (100% smashed rice straw, at 150 ); (c) test B14 (80% smashed rice straw/20% rice bran, at room temperature); and (d) test B18 (80% smashed rice straw/20% rice bran, at 150 °C).