3.2.2. The effect of the rice bran
At a fixed percentage of the rice bran, both the air-dry density and
the compressive strength of the briquette with the smashed rice straw
(b2 mm) increase as the hot-pressing temperature increases. This
tendency is similar to that of the briquette with 100% of the smashed
rice straw. For example, for a briquette with 20% of the rice bran, as the
hot-pressing temperature increases from the room temperature (test
B14) to 150 °C (test B18), the air-dry density substantially increases
from 0.57 to 1.02 g/cm3, and the compressive strength significantly
increases from 4.1 to 85.0 kgf/cm2. These results can be explained by
the structure of the briquette. Comparing with Fig. 7(c) in test B14 and
Fig. 7(d) in test B18, the structure of the briquette in test B18 (150 °C)
is more compact than that of the briquette in test B14 (the room
temperature)