Fuel quality and dry matter losses of stored wood chips - Influence of cover material

Irregular seasonal demand from heat- and combined heat and power plants means that outdoor storage of forest fuels is an inevitable step in the forest fuel supply chain. Storage of fresh comminuted biomass render substantial dry matter and energy losses. Covering can protect wood chips from rewetting, leading to a higher net calorific value and lower dry matter losses, and thus increase the amount of available energy. This study examined the combined effect of covering material on fuel quality and the amount available energy from wood chips stored in a full-scale pile. The combined changes in fuel quality and dry matter loss reduced the amount of accessible energy by 9.8% in the uncovered part, by 5.6% when covered with water proof or light semi-permeable cover materials and by 1.0% when covered with a thicker semi permeable material. Fuel quality of wood chips can be improved by covering the piles during storage but the gain is affected by the type of cover material. Seasonal storage in properly covered chip piles facilitate an increased annual utilisation of chippers and chip trucks which reduces overall biomass supply chain cost