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The Critical Moisture Range for Rapid Microbial Decomposition of Rice Straw During Storage

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Transactions of the ASABE. 52(2): 673-677. (doi: 10.13031/2013.26806) @2009
Authors:   A. P. Reddy, B. M. Jenkins, J. S. VanderGheynst
Keywords:   Biological activity, Moisture content, Respiration, Rice straw, Self-heating

Proper design of biomass storage systems is a critical factor facing lignocellulose-based industries. Improper storage conditions can result in decomposition and deterioration of biomass, and self-heating to the point of ignition. The goal of this research was to characterize microbial activity on a model lignocellulosic resource, rice straw, between 20% and 200% moisture content on a dry basis (d.b.) at 25C and 35C. Microbial activity was determined from CO2 evolution rate measurements made on batch incubations of wetted straw. The threshold moisture content below which microbial activity would not occur was found to be between 29% and 41% d.b. Microbial activity, represented as peak and cumulative carbon dioxide evolved, followed a sigmoidal relationship with respect to moisture content; activity increased exponentially with moisture contents between 30% and 100% d.b. and then leveled off between 100% and 250% d.b. The rate at which the biomass achieved peak activity increased with increasing moisture. Activity and the rate of self-heating were greater at 35C compared to 25C and suggest a greater risk for biomass deterioration, self-heating, and thermal runaway conditions under higher mesophilic temperatures.

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