Additives play a major role in wood pellet characteristics and are a subject of major interest as they act as binding agents for the biomass raw material. Past research has reported the use of lignosulphonate, dolomite, starches, potato flour and peel, and some motor and vegetable oils as additives for wood pellet production. This paper reviews the available research on the effect of different additives on wood pellets' physical and thermal characteristics. It was found that lignosulphonate and starch additives improve the mechanical durability but tend to reduce the calorific value of the wood pellets. Motor and vegetable oil additives increase the calorific value minimally but significantly increase carbon monoxide emissions. Corn starch and dolomite additives also significantly increase carbon monoxide emissions. In order to produce wood pellets with desired physical and thermal characteristics, a suitable additive with the right biomass material should be used. 1. Introduction The Canadian government is promoting clean energy usage; accordingly, the provincial governments have chalked out plans to become completely coal-free in the near future [1]. However, according to the International Energy Agency, in 2009, wood energy that is considered clean comprised only 4% of Canada’s total primary energy supplies [2]. Wood pellets have emerged as a very successful renewable fuel source for energy production, due mainly to their many beneficial characteristics, including high density and calorific value, low moisture content, and relative convenience of transportation and storage. Wood pellets are wood fuel made from compacted sawdust and other wood waste [3]. Residential use of the prime class wood pellets have ？mm diameter and 3.15–40？mm length (EU standards) [4], and 5.84–7.25？mm diameter and ？mm length (USA Standards) [5]. Canada is emerging as one of the world leaders in wood pellet production. The wood pellet production capacity in Canada has grown from 300,000 tonnes in 1997 to 2.93 million tonnes in 2011 [6, 7]. This growth is due in part to the European Union’s (EU) renewable energy promotion policy, as 90% of total Canadian pellet production goes overseas while domestic usage is extremely low [8]. Price of wood pellets in Europe ranges from US 215 to US 275 per tonne, whereas in the North American market, the average domestic residential retail price ranges from US 175 to US 250 per tonne [9]. Wood pellet production plants are present in almost all provinces of Canada, but the majority of pellet production comes from Western Canada (British
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