This study investigates the recovery of fermentable sugars from durian peel using ultrasound-assisted chemical pretreatment. Durian peel, a common agricultural waste in Malaysia, contains high levels of cellulose, hemicellulose, and lignin, making it a promising feedstock for biofuel production. Traditional chemical pretreatments, such as acid or alkaline treatments, often require extensive washing and generate significant wastewater. To address these issues, this study combines ultrasound with chemical pretreatment to enhance sugar recovery while reducing chemical usage. The study used sulfuric acid and sodium hydroxide as chemical pretreatments, with and without ultrasound assistance. The pretreated durian peels were analyzed using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) to assess structural and chemical changes. SEM images showed that ultrasound significantly altered the structure of durian peels, increasing pore formation and improving accessibility for enzymatic hydrolysis. FTIR analysis indicated that ultrasound-assisted pretreatment reduced the intensity of lignin and hemicellulose, enhancing sugar release. XRD results showed that ultrasound-assisted pretreatment increased the crystallinity index, suggesting more effective lignin removal. The study found that ultrasound-assisted pretreatment significantly increased the yield of fermentable sugars compared to conventional methods. The highest sugar yield was achieved with ultrasound-assisted alkaline pretreatment (UB), producing 376.60 ± 12.14 mg reducing sugar/g dry biomass. This method also improved enzymatic hydrolysis efficiency, with UB showing a 26.06% increase compared to its control. Fermentation of UB-treated durian peel resulted in a hydrogen yield of 2.68 mol H₂/mol sugar consumed and a hydrogen productivity of 131.56 mL/L medium/h. The study concludes that ultrasound-assisted chemical pretreatment is an effective method for enhancing sugar recovery from durian peel, reducing chemical usage, and improving the efficiency of biofuel production. This approach offers a sustainable solution for managing durian waste and generating valuable fermentable sugars for high-value biochemical products.This study investigates the recovery of fermentable sugars from durian peel using ultrasound-assisted chemical pretreatment. Durian peel, a common agricultural waste in Malaysia, contains high levels of cellulose, hemicellulose, and lignin, making it a promising feedstock for biofuel production. Traditional chemical pretreatments, such as acid or alkaline treatments, often require extensive washing and generate significant wastewater. To address these issues, this study combines ultrasound with chemical pretreatment to enhance sugar recovery while reducing chemical usage. The study used sulfuric acid and sodium hydroxide as chemical pretreatments, with and without ultrasound assistance. The pretreated durian peels were analyzed using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) to assess structural and chemical changes. SEM images showed that ultrasound significantly altered the structure of durian peels, increasing pore formation and improving accessibility for enzymatic hydrolysis. FTIR analysis indicated that ultrasound-assisted pretreatment reduced the intensity of lignin and hemicellulose, enhancing sugar release. XRD results showed that ultrasound-assisted pretreatment increased the crystallinity index, suggesting more effective lignin removal. The study found that ultrasound-assisted pretreatment significantly increased the yield of fermentable sugars compared to conventional methods. The highest sugar yield was achieved with ultrasound-assisted alkaline pretreatment (UB), producing 376.60 ± 12.14 mg reducing sugar/g dry biomass. This method also improved enzymatic hydrolysis efficiency, with UB showing a 26.06% increase compared to its control. Fermentation of UB-treated durian peel resulted in a hydrogen yield of 2.68 mol H₂/mol sugar consumed and a hydrogen productivity of 131.56 mL/L medium/h. The study concludes that ultrasound-assisted chemical pretreatment is an effective method for enhancing sugar recovery from durian peel, reducing chemical usage, and improving the efficiency of biofuel production. This approach offers a sustainable solution for managing durian waste and generating valuable fermentable sugars for high-value biochemical products.