To elucidate the spontaneous oxidation and heat generation mechanism of carbonized biomass, its molecular structure was analyzed and compared with that of coal. It was found that a carbonized biomass sample (BP-A) has bigger cluster sizes and shorter side chains than that of the coal known for its high spontaneous heating tendency. Furthermore, the ESR spectrum of BP-A was measured while switching the atmosphere from N₂ to O₂ under heating conditions. While the radical concentration increased in the coal, it decreased in BP-A. These results suggest that BP-A exhibits a different low-temperature oxidation and heat generation mechanism compared to the coal.
