Assessing environmental costs and impacts of forestry activities: A multi-method approach to environmental accounting

摘要

Concerns about greenhouse gas emissions and a possible future shortage of fossil resources are leading to a growing demand for wood biomass as a renewable material and energy source. In this context, forestry activities are increasing to meet the larger demand for wood biomass supply. Hence, there is also an increasing need for assessing environmental costs and impacts of forestry operations, considering both direct and indirect inputs supporting wood production systems as well as main outputs, co-products, and by-products. In this study, a multi-method assessment encompassing material, energy, and emergy demand as well as relevant emissions was implemented to explore the environmental performance and sustainability of timber and wood biomass production in the Alpine context of Fiemme and Fassa Valleys, Province of Trento (Italy). The Energy Return On Investment (EROI) calculated for timber and wood chips production was 51.9 and 28.1. These output/input energy ratios showed that the products' energy content was high compared to the direct and indirect fossil energy invested in both production processes. The global to local ratio of abiotic material calculated for timber and wood chips was 3.58 and 2.95, proving that about 2 times more matter flows were extracted and processed elsewhere than locally to supply the production processes. The fraction of renewable emergy calculated for timber and wood chips was 81% and 75% while the Emergy Yield Ratio (EYR) was 4.57 and 3.86, respectively, proving that the forestry system is considerably supported by renewable and locally available resources. The release of CO_2 was 855 and 1331CO_2 /yr when considering the whole Fiemme and Fassa Valleys. These last figures, compared to the potential of the two valleys for greenhouse gas mitigation, showed the ability of the investigated forestry sector to perform within the limits of the local carrying capacity in terms of CO_2 emissions. Finally, the scenario analysis highlighted the maximum production level compatible with a sustainable forest exploitation. In conclusion, the development of a multi-method approach to environmental accounting allowed a comprehensive assessment of forestry operations, providing a tool useful for local managers and policy makers committed to implement an environmentally sound management of forestry activities.