Sensitivity of Technical Choices on the GHG Emissions and Expended Energy of Hydrotreated Renewable Jet Fuel from Microalgae

Abstract

Taking into account the environmental impacts of biofuel production is essential to develop new and innovative low-emission processes. The assessment of life cycle GreenHouse Gas (GHG) emissions of biofuel is mandatory for the countries of the European Union. New biomass resources that hardly compete with food crops are been developed increasingly. Microalgae are an interesting alternative to terrestrial biomass thanks to their high photosynthetic efficiency and their ability to accumulate lipids. This article provides an analysis of potential environmental impacts of the production of algal biofuel for aviation using the Life Cycle Assessment (LCA). Evaluated impacts are GHG emissions and the primary energy consumption, from extraction of raw materials to final waste treatment. This study compared two management choices for oilcakes generated after oil extraction from microalgae. In the first system, these cakes are treated by energetic allocation and in the second by anaerobic digestion. In both cases, the steps of cultivation and harvesting have the highest impact on the results. Sensitivity analyzes are performed on technical choices of operating systems (choice of the type of nutrients, mode of harvesting, drying and oil extraction) as well as a Monte-Carlo analysis on key parameter values for GHG emissions (concentration of microalgae in ponds, productivity and oil content). The results highlight the impact of the use of chemical fertilizers and the importance of the concentration of algae on GHG emissions and energy consumption.