Wood-based bioenergy value chain in mountain urban districts: An integrated environmental accounting framework

Using wood biomass for bioenergy production in mountain urban settlements can represent a win win strategy when it combines a continuous energy provision to households with a sustainable management of local forests, also boosting rural development and stakeholders' cooperation. In this study, we implemented a multi-method environmental accounting framework aimed at investigating environmental costs and impacts of a bioenergy value chain located in Sarentino Valley (North Italy). This assessment framework encompasses material, energy, and emergy demands as well as main emissions generated at each step of the chain: (1) forestry, (2) logistics, and (3) conversion. The resulting global to local ratios of abiotic material calculated for forestry, logistics, and conversion subsystems show that the global (direct and indirect) consumption of abiotic matter was respectively 3.6, 3.2, and 7.6 times higher than the direct material demand. The Energy Return on Energy Investment (EROI) of wood biomass and wood chips production (37.1 and 22.4) shows a high energy performance of these processes, while the EROI of heat generation (11.35) reflects a higher support of human driven inputs. The emergy renewable fraction, ranging from 77% to 37% across the value chain, shows a high use of local renewable resources in the bioenergy value chain. The total CO2 emissions of the bioenergy value chain (4088 t CO2 yr(-1)) represent only 7.1% of the CO2 sequestration potential of the Sarentino Valley forest ecosystem, highlighting the capability of the local forests to offset the CO2 emissions released by the value chain. The scenario analysis indicates that using both local sawmill residues and local forest wood chips to power the heating plant could further lower the environmental burden of the bioenergy chain, maximizing local and renewable resources use while reducing waste disposal. The multi-method environmental accounting framework provided a large set of performance and sustainability indicators useful for both local managers and policy makers in charge of ensuring a sustainable management of local forests and energy security of urban settlements. (C) 2016 Elsevier Ltd. All rights reserved.