From time immemorial, firewood has been a very important source of energy for mankind. Later in history, wood for energy decreased its importance because of other more convenient and cheaper sources, mainly fossil fuels. Today, focus is again on use of forests as a producer of energy with main drivers being climate change, shortage and increasing prices of fossil fuel sources, and safety in energy supplies. However, intensive use of forest biomass is qu- tioned since fundamental ecological processes may be influenced negatively thus making up a trade-off with the benefits of using an otherwise sustainable source of energy. In this book, selected aspects of intensive use of forest b- mass for energy is treated with main focus on ecological aspects like maintenance of soil fertility, recycling of the combustion ash, inf- ence on biodiversity and pests, and economical aspects both at forest owners level and for society. Another focus point is the implemen- tion of this knowledge into decision support, recommendations and guidelines. The geographical scope is mainly the Nordic and Baltic region. The EU-financed project “Wood for Energy, - a contribution to the development of sustainable forest Management” (WOOD-EN- 1 MAN) , make up the frame for the book. Seven partners participated in the project: Forest & Landscape Denmark, Swedish University of Agricultural Sciences, Finnish Forest Research Institute, Norwegian Forest and Landscape Institute, Lithuanian Forest Research Institute, Latvian State Forestry Research Institute, and Estonian University of Life Sciences with Forest & Landscape Denmark as coordinator.