Effective pretreatment of wet microalgal biomass to enhance lipid extraction in biodiesel production

Biodiesel is a viable alternative to fossil fuels. Identifying and evaluating nonedible sources is essential to address ecological concerns and meet energy demands. Microalgae are effective for lipid production but their rigid cell walls hinder bioproduct release making the process energy-intensive and costly. This affects the economic feasibility of biorefineries significantly. Dewatering microalgal biomass also 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 homogenization, applied to the microalgal species Chlorella vulgaris and Nannochloropsis oculata. Maximum lipid yields of 15.24% for C. vulgaris and 29.98% for N. oculata were achieved using microwave treatment at 600 W for 135 s and 4 h of extraction time. Similarly, high-speed homogenization at 22 000 rpm for 10 min and 2 h of extraction yielded 18.65% and 40.56% lipid content in C. vulgaris and N. oculata, respectively. Response surface methodology (RSM) was employed to evaluate the effects of various pretreatment conditions on lipid yield. The results indicate that high-speed homogenization enhanced lipid extraction efficiency. The findings provide new insights for optimizing mechanical pretreatments for microalgae-based biodiesel production and other bioproducts.