Life cycle assessment of residual forestry biomass chips at a power plant: a Portuguese case study

The residual forest biomass (RFB) sector has been experiencing strong development at European level and particularly in Portugal mainly due to the increase of energy production from renewable sources. The aim of this study is to assess the environmental impacts of eucalyptus RFB chips production chain in Portugal. The environmental and economic impact comparison of the processes included in the production chain is presented as well. The environmental impacts were calculated by the life cycle assessment approach described in the ISO 14040 series of standards. The production chain assessed included all processes from eucalyptus forest until the delivery of RFB chips at the power plant. The main conclusion of this study is that eucalyptus wood production is the process that presents the greatest environmental impact through the product life cycle. Considering only emissions and depletion of energy resources, RFB chipping is the process that presents the higher environmental impact followed by transport of RFB by truck and trailer and transport of RFB by forwarder. These operations are responsible for approximately 81 % on ‘‘Respiratory inorganic’’ and 87 % on ‘‘Fossil fuels’’ which are the two most significant normalized impact categories. In economic terms, the transport of RFB by truck and trailer presents the highest cost followed by chipping and processing of trees. These three operations are responsible for approximately 80 % of total costs. A sensitivity analysis showed that a 32 % increase in the transport distance from the forest to the power plant would cause an 8 % increase in ‘‘Climate change’’.