In the face of climate change, wood pellet is increasingly used as an replacement to coal or heating oil in residential heating and power generation. British Columbia is the Canadian biggest exporters of wood pellets with over one-million metric-tonnes produced in 2014. During the journey from the rainy BC coast to the consumers, pellets are exposed to weather element during loading at the port; pellet moisture content are increased from initial moisture content of 5%. Current loading protocol is to stop loading at any event of rain, regardless of the rain intensity, to prevent deterioration in pellet quality. However, some recent research observed that an increase from 5% to 8 or 9% in moisture content does not significantly decrease pellet durability, implying that pellet quality is acceptable at light rain conditions.
A robust experiment has to be conducted to confirm whether loading should be allowed under light rain conditions. With the financial support of the Pinnacle Renewable Energy Inc., my research simulated the different rain intensities by applying water on the pellets at different rates and time. It shows that at rain intensity less than 0.5 mm/hr, loading of pellets may continue for more than 1 hour, before mechanical durability of pellets drops below 96.5%. This result showed that loading of wood pellets during light rain conditions (rain intensity less than 0.5 mm/hr) may be continued for an extended amount of time.
The youtube video show a separate minor study on the swelling of wood pellets where the volume changes over time are measured. The objective of this test is to quantify the difference in the swelling volume between moist air wetting and spraying wetting. The pellets swell faster under moist air condition than spraying condition. This may be due to the slow adsorption of liquid water droplet through the pellet surface.
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