Emergy evaluation vs. life cycle-based embodied energy (solar, tidal and geothermal) of wood biomass resources

Several environmental accounting methods exist to evaluate the rate of ecosystems resource exploitation and to strengthen the comparison among human production systems in terms of renewability and sustainable use of resources. However, their application rarely refers to the environmental work that is necessary to produce natural resources. The aim of this research is to advance the characterization of different wood biomass species by using the emergy principles and thus to estimate the geobiosphere work required to generate wood resources. The analysis has been conducted applying the classical emergy methodology and a recently developed life cycle-based embodied energy approach. This latter is implemented with the support of Life Cycle Assessment (LCA) principles and tools to disclose as a result vectors of Unit Embodied Energy Value ((UEEV) over right arrow), composed by three components: the Embodied Solar, Tidal and Geothermal Energy. Differently from emergy evaluation, the life cycle-based embodied energy approach does not consider the baseline concept and the emergy algebra, but the Solar, Geothermal and Tidal sources are independently quantified, keeping them separated and not weighted. The present paper shows that the latter method can provide a consistent framework to trace and evaluate the primary provision of energy throughout the formation of resources. Regionalized UEVs (Unit Emergy Values) and ((UEEVs) over right arrow) have been obtained and compared with regard to Fagus spp., Quercus spp., Picea spp., Pinus spp., Pseudotsuga spp., Fraxinus spp., Populus spp., Castanea spp., and other grouped conifers (Larix spp., Cupressus spp. and Abies spp.) and other deciduous species (Carpinus spp., Betulus spp., Alnus spp. and Robinia spp.). The trend of output values per unit of resource species obtained by means of the two methods was very similar when looking at the Solar Embodied Energy contribution, meaning that this flow has the main direct (with the life cycle-based embodied energy approach) and indirect (with the emergy one) influence on the generation of wood biomass. Results obtained by means of both methods can fill out the life cycle of products based on wood biomass, providing the natural contribution to wood species formation and thus embedding this information in the technosphere processes. (C) 2013 Elsevier Ltd. All rights reserved.