Increasing the sustainability of photoautotrophic microalgae production by minimising freshwater requirements

There are now several companies that are producing microalgae such as Arthrospira platensis, Chlorella vulgaris, and Dunaliella salina, among others. They are cultivated mainly in large-scale raceway and tubular photobioreactors. Microalgae production represents a sustainable alternative to conventional biomass production. Microalgae can be used to manufacture agricultural products, animal feed, food and other commercial products. The water requirements for cultivating microalgae are significant, exceeding 1 m³·kg^-1. This value varies depending on the production strategy. One of the main reasons for water loss is evaporation, which is influenced by the photobioreactor location, the season, and the operating conditions. Efforts are being made to reduce water requirements and make microalgae production economically viable and more environmentally friendly. Several strategies are being investigated for reducing freshwater use in microalgae cultivation; these include reusing the culture medium and producing microalgae using seawater or wastewater. Such strategies not only reduce water consumption, but also reduce nutrient consumption and costs while increasing sustainability.