Life Cycle Assessment of Wood Pellet

Abstract

The primary purpose of this project is to assess the environmental impacts associated with the wood pellet production. The study has extended to the entire life cycle of wood pellet, which includes the up- and down-stream processes. Therefore it leaves the Life Cycle Assessment (LCA) the best method to carry out such study. LCA is a popular tool for evaluating environmental impacts of products or services. In this study, the mainstream LCA methodology is adopted, which includes four steps starting from goal and scope definition, life cycle inventory analysis, to life cycle impact assessment, and interpretation. The results of the study will be used for the wood pellet producer to communicate with its customers and also facilitate a better environmental management. The entire life cycle of wood pellet can be divided into eight main processes. According to the results of inventory analysis, the Silviculture is the most fossil fueldependant process, while the Pellet Production is, however, the most energy-intense process. Regarding the emissions, the final Combustion process contributes most to the air emissions, but the Pellet Production has a remarkably high emission of hydrocarbons, which can be explained as incomplete combustion of a mass of biofuel. The resources use, on the other hand, is close related to the consumption of electricity, since the electricity production is included in the system. The process with bigger demand of electricity results in bigger amount of resources use. When it comes to the characterisation level, the inventory data have been aggregated and translated into real environmental impacts. There are at least six different environmental impacts are possible to be initiated from the wood pellets production. It is noted that the Silviculture and the final Combustion are the least environmental preferable processes, due to the relatively big environmental impacts potential in relation to these two processes. There are three valuation methods involved in the report to weigh the importance of the environmental impacts against from one to another. The results of the three valuation methods are somehow different, which is, however, only because the methods tend to weight the importance of the environmental impacts from different perspective, and there is no such best weighting method exits. At last, a sensitivity analysis is given to discuss the hot points in the report, which is about to test the uncertainties of the data. Plus a discussion part is made at the end of the report to discuss the account of carbon dioxide emission in bioenergy system, and a crude comparison of avoided green house gas emission of using different kind of wood energy.