Ongoing progress on γ-irradiation technology for lignocellulosic biomass pretreatment in producing bioethanol

The growing demand for renewable energy has intensified research into bioethanol production from lignocellulosic biomass, a sustainable and abundant resource. However, the structural complexity and recalcitrance of lignocellulose require effective pretreatment to enhance enzymatic hydrolysis for bioethanol conversion. To address these challenges, gamma irradiation is emerging as one of the nonconventional pretreatments in addition to microwaves, electron beams, ultrasound, and X-rays, which are often used to break the bonds of lignin, cellulose, and hemicellulose and further degrade cellulose into simple sugars. This study explores the ongoing progress of gamma irradiation technology as an innovative pretreatment method for producing bioethanol. Moreover, the mechanisms and the effect of gamma irradiation on cellulose degradation and the surface morphology of irradiated biomass are also studied. Gamma irradiation integration with conventional pretreatment (e.g., NaOH 4%) on reed stalk biomass may lead to the highest cellulose enzymatic hydrolysis conversion rate, reaching 85.02% at 800 kGy. Compared to other radiation methods, gamma irradiation has more advantages with the deepest penetration and experienced high soluble sugars up to 55% at 2000 kGy from sugarcane bagasse. While gamma irradiation demonstrates considerable promise on the laboratory scale, economic and technical barriers remain for its industrial-scale application. Future research should optimize gamma irradiation parameters, explore hybrid pretreatment strategies, and expand its applicability to diverse biomass resources.