Using life cycle assessment (LCA) to evaluate the environmental characteristics of ethanol biorefinery

The main objective of this project is to identify suitable life cycle assessment (LCA)-based environmental metrics which can be used to assess the ethanol biorefinery, with emphasis on evaluating the co-products associated with different feedstocks.;After identifying the most appropriate LCA-based methodology, several scenarios were identified for the comparison of environmental advantages and disadvantages of ethanol production from different cellulosic biomass feedstocks. These scenarios included ethanol production from wood chips, an energy crop (triticale) and hemicellulose. These feedstocks can be used in greenfield ethanol production or at an Integrated Forest Biorefineries (IFBR) at an existing pulp and paper mill. The pulp and paper industry is an important Canadian industrial sector with many motivations for continuously improving its environmental performance from a life cycle perspective. Therefore, the application of LCA in pulp and paper process analysis has increased in recent years and there is a potential of using LCA in the assessment of process variants, in order to analyze the effect of mill modifications on the performance of the whole system. In this study two aspects of the IFBR were studied. ne process is a novel use of two processes, the first of which provides ethanol (main product) and energy (co-product) in the form of steam. This steam is then sent to the pulp mill in order to provide the additional energy required for the pulping by changing the type of generator used in the ethanol mill. The other aspect includes the extraction of hemicellulose from wood prior to pulping and converting it into ethanol, while using the remaining wood components to produce Kraft pulp. Two other scenarios include woodchips and triticale for greenfield ethanol production. Triticale which is a man-made crop developed by crossing wheat with rye, is grown widely in western Canada.;These scenarios were used to illustrate the proposed LCA methodology: (1) identification of relevant environmental metrics for ethanol production, (2) identification of aspects and monitoring the environmental performance of different scenarios for an ethanol biorefinery by utilizing these environmental metrics. These scenarios demonstrated that: (1) The development of metrics that quantify the environmental performance of production processes is an excellent way to integrate the goal of sustainability into decision-making. (2) Classical environmental metrics used for specific studies which are not by themselves adequate for selecting environmentally preferred ethanol Biorefinery options, should be enhanced by other appropriate metrics. (3) The sensitivity and scenario analysis parameters need to be selected in order to have a better understanding of the consequences on the results. In conclusion, the selection of the best methodological choices obtained according to the baseline model identifies the appropriate LCA methodology to make for the environmental evaluation of ethanol production. This methodology is then used in different scenarios to identify environmental opportunities for each of them. (Abstract shortened by UMI.);To meet the above objective, an LCA framework was built based on the assessment of a body of knowledge related to ethanol LCA studies. This assessment was done in order to identify some of the methodological choices according to their significance and their consequences for the final result. It focused on a survey of 26 LCA studies concerning the production of ethanol from different feedstocks. A critical review of the strengths and weaknesses of the different approaches was done to determine the impact of different methodological choices on the results. The review compared the results and consequences of each of the methodological choices which included choices such as the system boundaries, allocation procedures and environmental impact categories. To assess the impact of different methodological choices in an LCA, a base case was defined for application and comparison of these choices in order to assess their consequences and propose an alternative methodology for ethanol production assessments.