Emission of Volatile Organic Compounds from Softwood Pellets during Storage

The emission of volatile organic compounds (VOC) from fuel pellets made from fresh and stored Norway Spruce and Scots pine sawdust was investigated. Measurements were done by head-space (HS) and gas chromatographic mass spectrometric methods. It was found that pellets, under certain conditions, emit high levels of VOCs, especially volatile aldehydes but that the drying temperatures of sawdust and self-heating of stored pellets affect the composition of the emitted compounds. In pellets with a pungent smell, high levels of hexanal and pentanal together with minor amounts of other aldehydes were detected. A chemical characterization of sawdust and pellets was also done. During storage the amount of lipids was reduced due to oxidation. Spruce sawdust contained considerably lower amounts of fatty and resin acids than pine. Thus pellets made from stored sawdust might generate fewer VOCs than pellets made from fresh sawdust. Pellets made from Spruce sawdust emit fewer VOCs than pellets made from pine. It was also Concluded that the lipid content of sawdust could be used as a maturation indicator for sawdust.