Life cycle assessment e water footprint assessment nella progettazione di una filiera bosco-energia in Sardegna

The study of the potential environmental impacts of a hypothetical wood-energy supply chain has integrated: the application of models (particularly, spatial models), the chemical and physical characteristics of the forest biomass, the techno-economic viability of different plant configurations and the Life Cycle Assessment approach, for the sustainable design of a supply chain in its life cycle. The main results are relevant in the decision-making process, related to the installation of the chain. They allow the decision maker to select the most appropriate choices, between multiple scenarios, as well as between various improvement options and responses for the potential impacts reduction. The present study has developed an approach for the wood-energy supply chain design, which integrates its most significant components (the cultural heritage of the territory, the best forestry practices, the technological and economic issues related to the exploitation of forest resources), by interpreting them from the environmental viewpoint. Indeed, for a really sustainable supply chain, none of the abovementioned components should be excluded, being them connected each other. LCA provides a valid interpretation of the systems and product supply chains related to the forest biomass, both in terms of impacts on various environmental matrices, and from that of the related potential damage on the Areas of Protection (human health, ecosystem quality, resources). The methodology is, actually, widely used in ex-post evaluations of wood-energy sectors, but, on the contrary, it is poorly implemented for the feasibility study and design; thus, the present work could represent a reference point and a baseline for future studies, insights and improvements. The study area is the Monte Olia public forest, located in the Northern side of Sardinia Island (Italy) and managed by Ente Foreste della Sardegna. A Life Cycle Assessment has been performed on the potential supply chain, by considering its main phases. Firstly, the availability of forest biomass for energy purposes has been estimated. Then, each phase of the chain has been analysed, by applying average data from similar case studies, as well as by implementing spatial models and optimisation methods for the biomass transportation. The most economically viable plant configuration has been selected by carrying out a techno-economic and environmental analysis on different plant technologies for the energy conversion of woody biomass. It has taken into account the energy demand of the service buildings within the study area, along with the characterisation of the main forest species of the Monte Olia forest (by means of laboratory determinations). The water consumptions and the emissions into water in the Life Cycle Inventory have been used for the second part of the study, which has focused on the application of the Water Footprint Assessment methodology for the designed supply chain. The analyses have consisted in: the quantification and separation of the local water appropriation and of the external amounts; the identification of the most significant supply chain phases with reference to the freshwater appropriation; the comparison between the internal appropriation volumes (related to the annual energy production) and the annual rainfall on the study area. The Water Footprint Assessment results have led us to assert the sustainability of the supply chain, from the point of view of the local freshwater appropriation. Another objective has consisted in the comparison of the Water Footprints related to the specific wood-energy supply chain and to a similar chain fed with fossil fuels (oil-fired boiler, instead of the biomass boiler), by identifying the differences in terms of Water Footprint components. The results have confirmed the greater environmental sustainability of short supply chains fed with forest biomass, than those fossil fuel-dependent. The last objective has concerned the difference between the impacts on water obtained by LCA and the results of the Water Footprint Assessment. In the present study, Life Cycle Assessment and Water Footprint Assessment have been effective tools for the sustainable wood-energy supply chain design. The use of both methodologies has allowed us to identify some critical points in the use of LCA for the management of the freshwater resources, if not being used in synergy with the Water Footprint Assessment.