Life cycle assessment of microalgae derived biodiesel

Abstract

The primary purpose of this research was to determine the environmental impacts of microalgaederived biodiesel, through the use of real-world data. The secondary purpose was to propose methods to reduce the environmental impacts of the production of microalgae-derived biodiesel. The research and analysis were undertaken using data from three sites; 1. An autotrophic/heterotrophic based novel 1-hectare demonstration facility containing four 15m3 photobioreactor systems and various fermenter systems in Olhão, Portugal (part of the InteSusAl FP7 project) 2. A 1m3 novel bag based heterotrophic system in Wilton, UK (part of the Innovate UK BioMOD project) 3. A 100m3 photobioreactor based system in Lisbon, Portugal (part of the Horizon 2020 MAGNIFICENT project) The data from these three sites was used to construct LCA models within the software GaBi and OpenLCA, utilising Ecoinvent as the primary source of secondary data. Uncertainty analysis was undertaken through sensitivity analysis and through a Monte Carlo based method utilising pedigree matrices. Within this work, ReCiPe hierarchist midpoints and endpoints were considered, in addition to AR5 based climate change indicators (GTW100/20, GTP 100/50/20). The purpose of this work was to fill a current knowledge gap within the literature, where very few articles on the LCA of microalgae-derived biofuels (including biodiesel) consider data from real world facilities. In addition, no papers consider an autotrophic/heterotrophic based system such as that within this work. The LCA models constructed within this work, and the following publications in the literature, will fill this knowledge gap. The key findings of this work have been that; • Algae production facilities as described within this work currently produce higher impacts (AR5 and ReCiPe) than petroleum derived fossil fuels • As an animal feed alternative, algae does not compete well with soy, although this comparison is more favourable than with fuels. • The decisions made based on standard arithmetic models within OpenLCA are different to those decisions based on models involving pedigree matrix based Monte Carlo analysis. • Primary source of impacts were electricity and feedstock (yeast) • Infrastructure impacts could be reduced through using glass photobioreactors instead of glass. Life Cycle Assessment of microalgae-derived biodiesel Tom Bradley 2020

ii Key reconditions are; • Algae producers consider alternative products to produce from microalgae • Improvements of photobioreactors should be considered to reduce the electricity demand of pumps, even if this is at the expense of productivity • Productivity must be increased to at least >25.6 tonnes/hectare/year • Photobioreactors should be made from glass • There must be further research into uncertainty methods within LCA, and their impacts on decision making processes.