Sustainability of microalgae cultivation

Abstract

Abstract Outdoor microalgae cultivation is often heralded as intrinsically “sustainable” because it is based on the use of sunlight to convert carbon dioxide (CO2) and nutrients into biomass. However, engineering this natural process at an industrial scale requires land, energy, water, nutrients, and materials that must be processed and transported. Focusing on microalgae cultivation in open ponds, this chapter provides an overview of the state of the art in the field and discusses the most important impacts and contributors during microalgae cultivation. Despite considerable variability in the literature and lack of long-term full-scale data, microalgae cultivation for food production generally appears to be more sustainable than terrestrial crop farming in terms of land use efficiency and, when process water is properly managed, eutrophication potential. These environmental credentials can be considerably improved if seawater or brackish water can be used as process water for cultivation. The sustainability of microalgae cultivation for energy production can be challenged with regards to the use of fertilizers, fresh water, and energy. There is therefore considerable interest in microalgae-based wastewater treatment for enhanced biogas generation, but this entails additional costs and issues. It is, however, critical to remember no truly generic conclusion can be made and that a thorough life cycle analysis must still be conducted for each new microalgal application.