Eco-design of spirulina solar cultivation: Key aspects to reduce environmental impacts using Life Cycle Assessment

Abstract

To identify action levers that improve the environmental balance of Spirulina manufacture, this work presents an LCA study of a modelled Spirulina production coupled with Morris sensitivity analysis on the model parameters. The study concerns a hypothetical cultivation surface of 388.5 m2 in open and covered raceway ponds (ORP and CRP) under greenhouse located in the city of Nantes in France. Several environmental indicators were evaluated, though GWP (global warming potential) was chosen for deep results discussion. Results showed a large variability of GWP (global warming potential) indicator for both culture systems (from 15.5 up to 67.3 kg eq. CO2/kg biomass dw) depending on the three most impacting parameters (the use of a thermal regulation system for the culture medium, the low setpoint temperature regulation and the annual production period). Moreover, for both ORP and CRP systems, GWP reduction per kg of biomass is reached by avoiding all impacts related to thermal regulation (i.e. thermal energy, heat pump, etc.) and simultaneously yielding high biomass productivity. Hence, annual cultivation should be extended as long as suitable solar conditions are available for the growth of microalgae (high and long irradiation and high ambient temperature). Finally, both ORP and CRP systems reached similar annual production but have different GWP impact since (i) their needs of thermal energy are opposite in warm and cold periods and (ii) the impact related to the CRP infrastructure is almost twice the impact of the ORP infrastructure due to the CRP reactor cover.