Microalgae valorisation in different production sectors: A systematic review of life cycle assessment studies

Among the bio-based alternatives suitable to substitute fossil materials in various applications, microalgae are attracting attention. They can be exploited in several sectors such as the production of biofuels, biofertilisers, food, or chemicals. However, the potential environmental advantages of their use should be carefully assessed, with Life Cycle Assessment (LCA) being a well-established methodology for this purpose. This literature review analyses 92 LCAs performed in the five-year period preceding 2025, dealing with the valorisation of microalgae in all possible sectors. First, a critical analysis of the appropriate application of the LCA methodology is discussed. Then, the 41 comparative LCAs (i.e. studies in which an algal-based product is compared with a conventional one) are further analysed to understand the environmental convenience of the algal-based product. Concerning the LCA methodology application, shortcomings are found, observing that they can give misleading conclusions about the environmental performance/convenience of the studied systems. Criticalities are found mainly in terms of a limited number of assessed environmental issues (number of impact categories), lack of transparency, and poor data quality. Regarding the algal biomass exploitation, most of the comparative studies evaluate biofuels production. Other sectors are the synthesis of bioproducts to be applied on crops (e.g. biofertilisers and biostimulants), food, feed, bioplastics, and chemicals. Examining the environmental convenience of these sectors, none of them results particularly promising or penalising, with the outcomes being influenced by the peculiar characteristics of each specific assessed system. This underlines the importance of a broader application of LCA in the microalgae sector.