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).

Highlights

• This study established the Response Surface Methodology to get the optimal residual biomass in terms of invested and accumulated energy for thermochemical conversion.

• Fourier transform infrared spectroscopy was used to detect the biochemical composition of volatile matter in the residual biomass.

• A non-isothermal free model for the activation energy was implemented to find the relation according to the maximum temperature in biomass decomposition.

• The higher heating value obtained from the pyrolysis of residual biomass confirms it as a potential energy source based on a thermochemical conversion.

Keywords:

• Thermogravimetric characterization
• microalgae-yeast consortium
• bioenergy
• pyrolysis and statistical optimization

Acknowledgements

The authors give acknowledgment to the Laboratorio Nacional de Desarrollo y Aseguramiento de la Calidad de Biocombustibles (LaNDACBio), for allowing the use of laboratory infrastructure.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Jessica K. Suastes-Rivas

Jessica K. Suastes-Rivas: Conceptualization, methodology, writing - original draft.

Regina Aburto Barrera

Regina Aburto Barrera: Investigation, experimental data acquisition.

Violeta Y. Mena-Cervantes

Violeta Y Mena-Cervantes: Discussion of FT-IR analysis & funding acquisition

Isaac Chairez

Isaac Chairez: Discussion of regression model to predict the accumulated energy (higher heating value-HHV) in the residual biomass and discussion of response surface methodology.

Pablo René Díaz-Herrera

Pablo René Díaz-Herrera: Review & editing.

Raúl Hernández-Altamirano

Raúl Hernández-Altamirano: Conceptualization, investigation, writing - original draft.