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Research article - Peer-reviewed, 2018

VOC off-gassing from pelletized steam exploded softwood bark: Emissions at different industrial process steps

Boren, Eleonora; Larsson, Sylvia H.; Thyrel, Mikael; Averheim, Andreas; Brostrom, Markus


Formation of hazardous gases during transport and storage of biomass for large-scale bioenergy production is an important safety concern. While off-gassing has been addressed in numerous studies for raw woody biomass, very few describe it in the context of biomass for bioenergy production pre-treated by thermal technologies such as steam explosion. Volatile Organic Components (VOCs) are expected to be altered by the treatment, but until now there is no research published on VOC profiles of steam exploded materials in industrial scale. In the present study, VOCs emitted from the products were evaluated by sampling from different production steps from steam explosion of softwood bark, and following the production chain including also pelletization. Off-gasses were actively sampled using Tenax TA absorbent and analyzed by GC MS. The VOC formation dependency of operation and storage conditions at different process steps was evaluated by multivariate statistical analysis. We showed that the different process steps along the production line was the main influencing factor for VOC off gassing amounts, with highest VOC levels directly after the steam explosion process. Treatment severity mainly altered the relative composition of VOC profiles with more terpenes emitted from milder treatment, whereas more severe treatment shifted VOCs composition to contain more furans, e.g. furfural. In summary, treatment by steam explosion leads to potentially problematic VOC off-gassing profiles from the material, and levels vary considerable along the production line. The findings are important from a fuel handling and working environment perspective.


Tenax-TA; Thermally treated biomass; Pellet storage; Emissions; Furans; Terpenes

Published in

Fuel Processing Technology
2018, Volume: 171, pages: 70-77