H2 concentration of over 94% was contained in gases
collected during the period of temperature increase from 400 to
550 ◦C. However, concentration of H2 in gases collected for 30 min
while keeping temperature constant at 550 ◦C slightly decreased to
around 88%, and at this condition concentration of CH4 increases to
over 10% from below5% for gases collected from 400 to 550 ◦C.