Interest in feedstocks for pellet production has been increasing in the Terrace, B.C. area for a number of years. However, Terrace has one of the highest annual precipitation rates in Canada, and western hemlock, which has high green moisture content, is the predominant tree species. One of the critical factors affecting the financial viability of a pellet production plant is the moisture content of the feedstock utilized because it must be dried to approximately 10% moisture content before further processing. Drying of pellet feedstock is accomplished in large dryers that use hog fuel, pellet residuals, or natural gas as fuels. The higher the moisture content of the feedstock, the more biomass is necessary to fuel the dryer and the longer the feedstock remains in the dryer. Feedstock drying costs can be 20–50% of the total pellet production cost, depending on the initial moisture content of the feedstock and the fuels utilized to dry it.
Several storage methods and technologies have been considered to reduce moisture content, including seasoning logs in carefully configured pile shapes and in covered storage buildings. One of the most promising technologies consists of covering piles (pulp decks or residue piles) with “breathable tarps” that allow the moisture to evaporate from the deck or pile, yet prevent it from gaining moisture during rain or snow.
FPInnovations, in cooperation with BC Timber Sales and Coast Tsimshian Resources, performed a tarping trial in an attempt to maintain low moisture content of pulp logs in the Terrace region.