Harvesting of wood in an italian district: a quantitative stand-level analysis

To mitigate climate change, one of the most important ecosystem services provided by forests is the production of wood, that can be used both for long life-cycle wood products and to generate energy (thermal, TE; electric, EE; GJ). The analysis of wood supply is essential: (i) to support local Authorities and supply chain operators in sustainable forest management, and (ii) to promote the transition into a low-carbon emission economy. The studies that quantify wood supply are still few and generally based on data coming from forest inventories or remote sensing, and rarely take into account site-specific primary data collected in the Forest Management Plans (FMP). In this study – carried out considering 45 FMPs located in the Valle Camonica District (Northern Italy) – data related to 2019 forest stands (total area: 3.67∙104 ha) were analyzed, showing that – in the period 1984-2016 – wood was harvested 4333 times in 1215 stands (60% of the total). The collected data were organized in the model WOody biomass and Carbon ASsessment (WOCAS v2), able to calculate – at the stand level – the masses of: (i) harvested stem (Sh; t·ha-1·yr-1 dry matter, hereafter DM), (ii) produced logging residues (Rp; t·ha-1·yr-1 DM), (iii) harvestable logging residues usable for energy conversion (Rh; t·ha-1·yr-1 DM), and (iv) stored carbon (Cm; t·ha-1·yr-1 C) within the stand. Results show that in the District: the total harvested stem is Sh_tot = 1.25∙105 t DM; logging residues reach 4.04∙104 and 2.70∙104 t DM for Rp and Rh, respectively. Assuming that Rh is transformed into woodchips (1.13÷1.32∙104 toe, corresponding to 4.72÷5.52∙105 GJ) to feed local cogeneration central heating plants equipped with Organic Rankine Cycle (ORC), the cogenerated thermal and electric energy are: TE = 2.63÷3.08∙105 GJ and EE = 5.99÷7.01∙104 GJ, respectively. Moreover, if cogenerated energies substitute both the natural gas (the most widespread fossil fuel used in the District for heat generation) and the grid electricity (made by the Italian electrical production mix, based on fossil and renewable energy sources), the avoided emissions into the atmosphere (excluding the transport phase of the wood-to-energy chain) are equal to 2.25 ÷2.63∙104 t CO2.