Enhancing bio-hydrogen and biogas yields through optimized ultrasonic pretreatment of algal biomass for sustainable energy production

• Ultrasonic (US) pretreatment boosts biogas & bio-hydrogen from algae; best yield at 373 ml, 32.7 %. • RSM optimized US pretreatment; shorter sonication boosts biogas yield. • US pretreatment boosts algal biofuel yield by enhancing cell wall breakdown. • US pretreatment optimization; 5-min sonication tops at 382.68 ml, 4.66 ml/hr. Algae are a promising resource for sustainable energy production, including biogas and bio-hydrogen. This study investigates the effect of ultrasonic (US) pretreatment on Enteromorpha algae to enhance biogas yields. Using response surface methodology (RSM), three key parameters—sonication time, amplitude, and liquid-to-solid ratio—were optimized, with cumulative biogas production as the response. The optimal conditions (5 min sonication, 30 % amplitude, 20:1 liquid-to-solid ratio) resulted in a maximum cumulative biogas production of 373 ml and a bio-hydrogen yield of 32.7 % (v/v). Scanning electron microscopy (SEM) revealed significant cell wall disruption, enhancing substrate availability for microbial digestion. However, prolonged sonication reduced yields due to inhibitory effects. Kinetic modeling with Modified Gompertz and Logistic Function models demonstrated faster reaction rates and higher production potentials for pretreated samples. This study highlights the potential of US pretreatment for improving the biodegradability of algae, offering an efficient and sustainable method for bioenergy production .