WPAC Report Proper handling New safety data sheet for wood pellets By Gord Murray hen handled properly, wood pellet fuel is safe and be-nign. Wood pellets are made by drying and compressing pure wood particles. Naturally occurring lignin softens during pelletizing and then hardens during the cooling process to bind wood particles together as pellets. It is hard to imagine how such a pure product could be dangerous. Unfortu-nately, over the years, there have been instances where wood pellets have been handled improperly, resulting in serious injuries and even fatalities. In May 2002, during the discharge of pellets from British Columbia onboard MV Weaver Arrow in the Port of Rot-terdam, one stevedore died and several other workers were injured after enter-ing a ship hold where wood pellets had generated carbon monoxide (CO). A similar fatal case occurred in November 2006 onboard the MS Saga Spray in the Port of Helsingborg, Sweden, while the vessel was, again, discharging wood pel-lets from British Columbia. One seaman was killed, a stevedore was seriously in-jured and several rescue workers were slightly injured after entering an unven-tilated stairway next to a cargo hold. Other incidents caused by the re-lease of carbon monoxide from wood pellets have occurred beyond ships’ cargo holds, including three deaths in Europe since 2010, caused by entry into wood pellet storage facilities on domes-tic sites. At the end of January 2010, a 43-year-old engineer died in a small town in Germany after he opened a pel-let bunker door. A second worker who was standing right behind him was also affected but still able to call the emer-gency services. The pellet bunker had a storage capacity of approximately 155 W tons of pellets, supplying about 700 households with heat. In November 2010, a 38-year-old man in Ireland died after entering the 7-tonne wood pellet storage room for his boiler. His wife and another man were treated in hospital after trying to pull him to safety. Another fatality occurred in February 2011 in Switzerland, where a 28-year-old woman who was four months preg-nant was found dead in an 82-m 3 pel-let storeroom. The wood pellet heating system supplied 60 households. In this instance, there was a problem with the wood pellet conveyor, so the caretaker’s wife went to inspect the problem on his behalf. As the woman’s body was found almost completely wedged beneath the circular cover above the opening of the screw conveyor, it was initially assumed that the accident was primarily of a me-chanical nature. However, when exter-nal examination of the body revealed bright red lividity of the skin and fin-gernail beds, giving rise to the suspicion of CO poisoning, the body was sent for a full postmortem examination. The main hazards from wood pellets are: • Wood pellets generate CO and cause oxygen depletion. This means that closed storage spaces must be ventilated and tested for the presence of CO before a person can enter safely. • Dust from wood pellets in high concentrations is explosive if ex-posed to an ignition source. To prevent explosions, wood dust should not be allowed to accumu-late beyond 3-mm depth. Electri-cal equipment near wood pellets should be grounded to prevent static discharge. Cleaning of stor-age and work areas should be done by sweeping or with the use of an electrostatically secure vacuum sys-tem. Never use compressed air for clean-up. If a front loader is used for moving wood pellets on the floor, the edge of the bucket pen-etrating the floor shall be equipped with non-metallic electrically dissi-pative material to avoid electrostat-ic build-up and sparks. • For sensitive persons, wood pellet dust may cause mild skin irritation, may cause allergy or asthma symp-toms if inhaled. • When exposed to moisture and temperatures above 60C, wood pellets are susceptible to self-heat-ing and the potential to catch on fire. Ideally, wood pellets should be stored below 30C. In large-scale storage, temperature sensors con-nected to an alarm system are rec-ommended to detect high tempera-tures and potential fires. • When exposed to water, wood pel-lets will swell by about three to four times. This means that water should not be used for fire fighting in enclosed pellet storage vessels. Instead, nitrogen and carbon diox-ide should be used for fire fighting. • If pellets do catch on fire, punc-turing storage containment is not recommended since the pyrolysis gases developed inside the con-tainment are highly flammable and might explode or violently catch fire once in contact with air. Following the 2002 fatality in Rotter-dam, WPAC’s research director Staffan Melin created a material safety data sheet (MSDS) which described the haz-OCTOBER 2016 8 Canadian BIOMASS
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