Bioenergy enhancement for isolated microalgae-yeast cocultured residual biomass as a function of inorganic micronutrients’ distribution

Abstract

This research aims to get the statistical optimization of the higher heating value for residual biomass of a coculture conformed of microalgae and yeast species (CCMY). The CCMY was grown in different culture broths with micronutrient (N, P, and Fe) distributions defined by the Box-Behnken experimental design. Lipids in the cultured biomass were removed by the reactive extraction method. Fourier transform infrared spectroscopy (FTIR) confirmed that biomass compounds were susceptible to applying thermogravimetric characterization. A pyrolysis process determines the invested energy and accumulated energy during biomass thermal degradation. The pyrolysis process evaluated the thermogravimetric analysis (TGA), yielding the determination of the amount of volatile matter, fixed carbon, and ashes in terms of the nutrient’s distributions. The obtained volatile matter range was 50.57-69.27%, fixed coal from 19.61-22.77% and the ash content was between 7.04 and 19.94%. The optimization problem considers that the accumulated energy is a function of the culture broth micronutrients’ distribution. Applying the response surface method (RSM) over the experimental design data leads to determining the best nutrient combination that produces the higher heating value in the residual biomass (22.04 MJ/kg, dry-basis biomass).