Viability of biodiesel production from a thermophilic microalga in conventional and alternative culture media

Abstract

Microalgae biodiesel production depends on several factors to minimize the costs of the production process from both biomass and biodiesel. In some outdoor systems, the temperature can be higher than 35 °C, which is lethal for several algae. Prospecting microalga from thermal environments seems to be a good option. Therefore, the objective of this work was to isolate a microalga (Acutodesmus obliquus (Turpin) Hegewald and Hanagata) from thermal water and evaluate its cultivation productivity in Bold Basal Medium (BBM) and in lower cost alternative media. One alternative medium contained only the main growth ingredients (DAF), the other included these same ingredients with the addition of wastewater from the purification of grease-based raw materials (DAF + OGR). Microalga biodiesel productivity was also compared with the biodiesel yield of soybean, which is one of the main raw materials currently used for biodiesel production. The microalga was shown to provide biomass with similar productivity using the three different culture media in log phase. The microalga exhibited biodiesel productivity from 46 to 61 times higher than soybean; using 5.5–7.2% of the water and 1.6–2.2% of the land required for soybean cultivation to produce the same amount of biodiesel. The DAF + OGR medium, which costs 29% of the cost of the BBM medium, proved to be an efficient alternative medium compared to other in biomass productivity. Levels of tri-unsaturated and polyunsaturated fatty acids from A. obliquus microalga were slightly higher than those standardized by EN14214, requiring that the biodiesel be mixed with antioxidants.