Life cycle assessment of the production of the red antioxidant carotenoid astaxanthin by microalgae: From lab to pilot scale

The freshwater green microalga Haematococcus pluvialis is the richest source of natural astaxanthin. Astaxanthin is a high-value red carotenoid pigment commonly used in the food, feed and cosmetics industries due to its well-known antioxidant, anti-inflammatory and antitumour properties. This study assesses the environmental impacts associated with the production of natural astaxanthin from H. pluvialis at both lab and pilot scale. Closed airlift photobioreactors with artificial illumination, typically used for the production of high-value products to avoid contamination risks and allow controlled lighting conditions, were considered. The study extends from the production of the different inputs to the system to microalgal production, harvesting and further extraction of the carotenoid. The life cycle assessment was performed following the ISO 14040 and ten impact categories were considered in the study: abiotic depletion, acidification, eutrophication, global warming, ozone layer depletion, human toxicity, freshwater aquatic ecotoxicity, marine aquatic ecotoxicity, terrestrial ecotoxicity and photochemical oxidant formation. According to the results, electricity requirements represented the major contributor to the environmental burdens among the activities involved in the production of astaxanthin. For the lab-scale process, the air supply and the production of chemicals and lab materials were also significant contributors in several categories. In the pilot-scale production, the relative environmental impacts were greatly reduced, partially due to changes implemented in the system as a result of lab-scale environmental assessment. However, the production of electricity still dominated the impacts in all categories, particularly due to the cultivation stage. For this reason, a sensitivity assessment was proposed in order to identify alternative photobioreactor configurations for astaxanthin production. Two of the evaluated options, based on the use of sunlight instead of artificial illumination, presented significant reductions of impact. However, the improvements observed in these cases were limited by the decrease in biomass productivity associated with sunlight culture systems. Therefore, a two flat-panel photobioreactor system with artificial illumination is proposed as a suitable option, allowing reductions between 62% and 79% of the impact depending on the considered category.