Dry matter losses can be a remarkable cost factor and emission source in biomass supply for energy and biorefining. Roundwood is not sensitive for dry matter losses and that is why storing along a supply chain and in terminals should be focused on roundwood, if possible. Within harvesting residues and comminuted material, dry matter loss of 1% per month is an appropriate figure to be used in inventory calculations. In worst cases, dry matter losses can be close to 3% per month. The measurement of dry matter losses is challenging and despite of serious efforts, the predicting of losses and their biological and physical processes are not known wellenough.