Effective pretreatment techniques on wet microalgal biomass for enhanced lipid extraction in biodiesel production

Biodiesel is considered a viable alternative to fossil fuels; therefore, identifying and evaluating non-edible sources is essential to address ecological concerns and energy demands. Microalgae are effective in lipid production, but their rigid cell walls hinder bioproduct release, making the process energy-intensive and costly. This significantly affects the economic feasibility of biorefineries. Moreover, dewatering microalgal biomass remains a technical challenge. Despite recent progress in wet biomass-based biodiesel production, its cost remains higher than that of traditional diesel. This study investigated two laboratory-scale mechanical pretreatment techniques; microwave irradiation and high-speed homogenisation applied to the microalgal species Chlorella vulgaris and Nannochloropsis oculata. Maximum lipid extractions of 15.24% in C. vulgaris and 29.98% in N. oculata were achieved using micro-wave treatment at 600 W for 135 seconds and 4 hours of extraction time. Similarly, high-speed homogenisation at 22,000 rpm for 10 min and 2 hours of extraction yielded 18.65% and 40.56% lipid content in C. vulgaris and N. oculata, respectively. A Response Surface Methodology (RSM) was employed to evaluate the effects of various pretreatment conditions on lipid yield. Results indicate that high-speed homogenisation enhances lipid extraction efficiency compared to earlier studies. The findings offer new insights into optimising mechanical pretreatments for microalgae-based biodiesel production and other bioproducts.