Wood Pellet Properties Produced in British Columbia and Studies on Off-Gas Emissions at Low and High Storage Temperatures

Abstract

In the present study the physical properties of wood pellets produced in British Columbia for a period of 1.5 years were studied. The wood pellets were procured from Fibreco Export Inc., North Vancouver, BC, Canada, a local shipping company and a leading supplier of wood chips and pellets to major countries in Europe. Pellets were collected at the shipping point approximately for every 1.5 to 2 months time period. The physical properties of the wood pellets studied were moisture content, bulk & tapped density, pellet density, durability, percent fines, calorific value and ash content. The variability in the measured data was measured using standard deviation. Results indicated that the pellet properties moisture content, bulk density, particle density, durability and percent fines were in the range of 3.5-6.5 %, 700-800 kg/m3, 800-900 kg/m3, 1125-1175 kg/m3, 65-75 %, 0.04-0.14 %, 18-19 MJ/kg and 0.2 -0.9 %. The diameter and length were in the range of 6.4-6.5 mm and 14.0 to 19.0 mm. The results also indicated that higher ash content has reduced the calorific value, bulk density, durability and length of the pellets. The pellet properties measured were found to be significantly different at P<0.001. The study indicated that the quality of the pellets produced and exported to Europe are according to the national standards. Studies on off-gas emissions like CO, CO2 and CH4 and O2 depletion from headspace were carried out using glass canisters of 270 110 mm (L D) at storage temperatures of 5-40C. Commercial refrigerators and laboratory ovens were used to for low and high temperature studies. The results indicated that the emission of off-gases CO, CO2 and CH4 and depletion of O2 in the headspace were significantly low at 5, 10 and 20 compared to 40C. At 5C the maximum CO2 and CO concentrations observed were 1000 and 500 ppm whereas at 40 the maximum CO and CO2 concentration observed were 15989 and 25456 ppm for 23 of storage period. In addition to that the O2 concentration recorded at 5 and 40C in the headspace at the end of 23 days of storage period was 19.5 % and 2.1 %. There is no significant change in wood pellet properties during storage except the durability values has reduced by 3 %.