Research experience from the use of different additives in wood-fuel pellet production

Abstract

The use of wood-fuel pellets has increased significantly worldwide in recent years, especially in the United Kingdom. If wood-fuel pellets should continue to be a successful biofuel at the energy market, the pellet production industry has to reduce the production cost, since it is a low-margin business. Further, improved pellets regarding storability and strength of the pellets are crucial to manage the overseas transportation that causes material losses. In addition, the industry tries to produce pellets from a broader raw material base and at the same time satisfy the customer requirements while producing a sustainable product. The wood-fuel pellet industry has the possibility to meet all these criteria; however, it also has the potential for improvements. Using additives in pellet production is one way to meet the criteria. In conclusion, it is necessary to do the research that systematically investigates the consequences of using additives for wood-fuel pellets, and this work presents a compilation of results and experiences from more than 20 different additive studies and the test bed for pellet production research at Karlstad University– a pellet production unit adapted for additives studies. Additives, with an admixture of up to 2% (wt.), have been tested in the NewDeP (New Development for Pellet Technology) pilot plant for pellet production at Karlstad University. The research has focused on the electricity consumption, the physical and mechanical properties of the pellets, and the CO2 equivalents emitted during production. The results showed that the additives Wetland grass, Algae, Turpentine and Lignin decreased the electricity consumption in the pellet press but unfortunately also decreased the durability. The additives Resins, Molasses, White sugar, Native potato starch and Oxidized potato starch increased the durability of the pellet but showed almost no change in the electricity consumption. However, Oxidized corn starch, Spent sulphite liquor and Native wheat starch as additives increased the mechanical properties while it decreases both the electricity consumption and the climate impact, hence a Win-Win-Win situation.