Sustainable biodiesel production from microalgae cultivated in wastewater treatment ponds

Abstract

Microalgae-based biodiesel production has emerged as a promising avenue for renewable and sustainable energy sources. This thesis presents a comprehensive analysis of the technical feasibility and sustainability of microalgae-derived biodiesel production, focusing on cultivating indigenous mixed species in wastewater collected from rural oxidation ponds. Furthermore, a bi-functional KOH/rice bran-derived activated heterogeneous carbon catalyst was employed for the in-situ transesterification process and process parameters were utilized using statistical regression analysis by central composite design (CCD). The study includes microalgae cultivation sourced from a rural pond, providing a lab-scale demonstration of logistic growth patterns over two weeks. This approach showcases the potential to utilize wastewater as a growth medium, eliminating the need for additional nutrient supplementation and reducing freshwater consumption. Chlorophyll-A in wastewater confirms the presence of microalgae, setting the stage for a sustainable biomass source. A pivotal aspect of the research involves identifying and characterizing indigenous microalgae species. Morphological observations under the microscope provide valuable visual clues, while molecular techniques, including 16S rRNA gene sequencing and BLASTN searches, confirm the genetic identity of the strains as Desertifilum salkalinema and Chlorella vulgaris. Developing a novel bi-functional catalyst consisting of KOH impregnated on rice bran-derived activated carbon support material represents a significant milestone. Characterized through scanning electron microscopy (SEM) and X-ray diffraction (XRD), this catalyst enhanced the efficiency of in situ transesterification by effectively filling porous structures. Exploration of solvent combinations for direct transesterification with synthesized catalyst was carried out. In-situ transesterification with H2SO4 was carried out to find the most suitable vi combination. The successful identification of methanol and hexane as the