Environmental impact assessment of wood products for bioenergy in Europe

In the last years the world energy demand has rapidly increased as a consequence of the worldwide economic growth and development and it is expected to increase faster in the next decades. Therefore the replacement of fossil fuels with renewable resources is considered to be crucial. Among different ways of producing renewable energy, biomass represents one of the most promising energy source. In this context, this work aims to compare the environmental impacts of different biomass supply chains, as firewood and pellet produced in Europe. The differences between the biomass supply chains are assessed through a “gate to grave”. Life Cycle Assessment for the impact categories: Global Warming Potential (GWP) and Ozone Depletion Potential (ODP); Photochemical Ozone Creation Potential (POCP) and Human Toxicity Potential (HTP). The boundary of LCA takes into account the forest operations and does not consider tree seedling, site preparation, fertilizer and herbicide treatments because of the naturalistic silvicultural practice used in Italy. The environmental impacts were calculated based on the method CML 2001 – Apr. 2013 from the Leiden University. The functional unit is 1 MJ of energy for domestic heating. The majority of the emissions are constituted of biogenic carbon dioxide produced by the biomass combustion. In the case of firewood supply chain, the study has outlined that for the short supply chain the critical phase of the life cycle in terms of GWP, POCP and HTP is combustion. Moving to the long supply chain, the on-road transport is the most critical phase: the contribution to GWP becomes more than double than the short supply chain and five times higher to ODP. Concerning the pellet supply chain, it was found that some specific processes (burning, drying, pelletizing) are the biggest contributors for all the four impact categories. Comparing the two biomass production, firewood shows the lowest impacts because of the less energy intensive production processes. Although most of the chemicals emitted in the life cycle of biomass cannot be offset, a sustainable naturalistic forest management, common practice in Italy, can completely offset the fossil CO2 emissions, the largest emissive component of greenhouse gases.