The potential of energy utilization from logging residues with regard to the availability of ashes

This paper evaluates the conditions under which the availability of ashes suitable for recycling limits the expansion of a sustainable energy harvest of logging residues from the forest. One of the major potentials that could increase the use of bioenergy in Sweden is the use of logging residues—tops and branches—that are now left behind in the forest. To avoid nutrient depletion and increased acidification, wood ashes should be recycled to the forest ecosystem. An increased use of logging residues will lead to a higher demand for recyclable ashes. The harvest of logging residues will probably be restricted if the available amount of ashes is less than the demand. A model is developed for the relation between the energy potential of the logging residues that could be utilized, the loss of nutrients in the technical chain, the available amount of wood ash from other sectors, and the level of nutrient compensation in the forest. The results indicate that the availability of ashes suitable for recycling will not limit the expansion of energy from logging residues if the loss of nutrients in the technical chain and the level of nutrient compensation are restricted. Actions in order to make this possible are proposed.