Abstract
Biodiesel is a renewable vehicle fuel based on biomass. Although environmental benefits can be assumed, both positive and negative impacts have been stated in the past, raising some doubts on the effective environmental performance of biofuels. They therefore need to be carefully examined through the established methods of Life Cycle Analysis (LCA). Such studies, though, have been known to give conflicting results and, for non-specialist users of environmental performance information, such variations in literature between studies will be a cause of concern. Following the principles of the ISO 14040 and 14044 standards for LCA, we have explored the variations in LCA methodology and parameter choices in a comparative analysis of 11 published studies of the production of biodiesel from palm oil. This study highlights inconsistencies between individual studies in aspects such as data coverage and completeness, system boundaries, and input and output streams. The importance of including factors such as plantation carbon sequestration and land use change demonstrates a need for consistent and appropriate methodologies. These factors are some of the most important drivers for variation in the results of LCA studies of palm oil systems, as well as being necessary for a comprehensive perspective. The results of this study also highlight the importance of geographical location and the fact that studies are often based on very limited data sources. A variance analysis identified the greatest source of variation across the chosen data sets, highlighting key methodology steps and pointed at pitfalls in employing supposedly environmentally benign technologies. The paper offers suggestions to i) assist inter-study comparisons, ii) offer non-LCA specialist users insight into the causes of variable results between LCA studies, and iii) guide further in-depth research.