Microalgae production in an industrial-scale photobioreactors plant: A comprehensive Life Cycle assessment

Abstract

Microalgae cultivation provides multiple opportunities to produce valuable bioproducts, but greater clarity must be achieved regarding the real sustainability of current technologies. Numerous life cycle assessment (LCA) studies have been conducted so far. However, most of them were based on literature data and/or extrapolations of lab-scale results, while only a few studies used primary data from pilot or full-scale microalgal plants. Moreover, the obtained results showed great variability, leaving the debate on microalgae sustainability fully open.This work presents a thorough LCA based on primary data from an industrial-scale microalgal facility located in Caltagirone, Italy. The plant is based on vertically-stacked horizontal photobioreactors (total volume of 40.4 m3) installed in a greenhouse and has a capacity of 1200 kgDW/y (Chlorella vulgaris). A cradle-to-gate assessment was performed with the functional unit of 1 kgDW biomass, including operational and infrastructural data. The results emphasized the key role in the generation of potential impacts played by cultivation among process stages and by chemicals (nutrients and cleaning agents) and electricity (mainly for agitation and thermoregulation) among flow types. In comparison with studies from the literature, the analysed microalgal plant has an intermediate environmental performance (e.g., global warming potential of 153 kg CO2,eq/kgDW). This result is encouraging, as it comes from a reliable assessment built on full-scale primary data. On the other hand, it highlights the need to explore alternative strategies (e.g., industrial symbiosis and circular bioeconomy) to reduce the environmental footprint of the process and enhance its economic attractiveness.