Moisture content effects on self-heating in stored biomass: An experimental study

Biomass is essential for modern bioenergy applications, but long-term storage of large volumes of it can pose challenges to plant safety due to the intrinsic self-heating characteristics of biomass piles. In recent years, serious fire accidents have occurred because of self-heating. However, little research has been conducted on this concern. The effects of different initial moisture contents (range of 20–95 %) on the self-heating characteristics of rice and wheat straw, which are two different agricultural biomass residues, are investigated in this study. Biomass samples with different initial moisture contents are stored in a well-insulated container, and the temperature and oxygen levels within the stored biomass samples are monitored. Based on the tests, the heat production rate, oxygen consumption rate and microorganism growth rate are derived, and the impacts of the initial moisture contents on the self-heating characteristics of the stored biomass samples are analysed. The highest temperatures in the stored rice straw and wheat straw are attained under initial moisture contents of 50 % and 20 %, respectively, while the largest heat production rates for both straw types are attained under an initial moisture content of 95 %. An increase in the initial moisture content greatly enhances the overall biological reactivity and oxygen consumption rate. The heat production and oxygen consumption levels exhibit a clear positive correlation. Under identical storage conditions, wheat straw is more susceptible to self-heating than rice straw, as shown by its higher heat generation, faster oxygen consumption, and shorter temperature peaking time. This study contributes to a quantitative understanding of the underlying processes and provides valuable experimental data for model development to guide safe biomass storage systems.