The current investigation focused on obtaining experimental results on self-heating properties of different woody biomasses during lab-scale storage. The heat released from the different biomass samples was measured by isothermal calorimetry, with the purpose to assess the contribution to self-heating during storage. Biomass samples were stored at different temperatures and metals were added in order to investigate if the presence of metals would increase the risk of self-heating. There was an increase in heat release after 10-30 days of storage, and the addition of metals gave rise to an increase in heat release. The results are intended to be useful when planning for the large-scale use of different biomasses, leading to the need of storage.