Correlation Between CO Off-gassing and Linoleic Fatty Acid Content of Wood Chips and Pellets

Abstract

During storage of wood pellets emissions of carbon monoxide (CO) and a large quantity of volatile organic compounds (VOCs) can be detected. These off-gases have been reported to originate from autooxidation reactions of woods own fatty acids, but data on CO formation rates based on fatty acid content is still scarce. In this paper data on the formation rates of CO from oxidation of pure linoleic acid are presented and compared to CO formation rates measured from spruce shavings, spruce sawdust and pellets made from the respective raw materials. To determine whether linoleic acid content is a realistic prediction tool for CO formation the fatty acid contents of the spruce materials have been determined and a comparison of predicted CO formation rates (based on linoleic acid content) to actually measured CO formation rates has been made. The results show that, albeit the fact that the determination of linoleic acid content is not the sole determining factor for an accurate prediction of CO formation rates, it is a helpful indicator in estimating a critical maximum rate of CO formation. The actual formation rates for CO, however, are typically lower than the predicted values and depend to a large extent on the history of the material and whether or not it has been activated. Activation includes treatments such as pelletizing, drying and/or milling.