Forest biomass sustainable use for energy production: A dynamic optimization problem

The use of forest biomass for energy production requires a careful attention to the sustainable silvicultural practices that can guarantee the satisfaction of the environmental constraints, the control of the forest growth, the carbon stock, and the CO 2 emissions. This is a complex task because of the different environmental and economic issues (related to the characteristics of the territory, the energy demand, the forest biomass potential production, and the techniques for forest utilization) to be taken into account. Environmental Decision Support Systems (EDSS) are considered as valuable tools for the planning and management of renewable resources use for energy production. In this paper, an EDSS for the tactical planning of forest biomass use (i.e., for the planning over a medium-short term horizon, within a discrete-time setting and the assumption that the plant capacity and the sizing of all facilities are known) is proposed. In particular, attention is focused on a dynamic decision model. An optimal control problem, whose control variables are represented by the biomass quantity to be harvested, is formalized and solved through mathematical programming techniques. The novelties of the proposed EDSS regard the dynamical formalization of an optimal control problem for a sustainable use of the forest resources for energy production, the possibility of including different forest growth models (embedded as constraints in the optimization problem) and a carbon sequestration model as a function of the control and state variables, an accurate definition of forest felling and processing, primary transportation, and transportation costs, a constraint that limits the yearly harvesting to the biomass mean annual increment (calculated as function of the average age and of the control variables). The EDSS has been tested within the Val Bormida mountain community (Savona District, Liguria Region, Italy).