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This paper critically reviews and discusses the utilization of ultrasound as an eco-friendly approach for enhancing biomass valorization efficiency. In contrast to other methods, this process requires no additional chemicals, no post-treatment (such as wastewater treatment), and helps achieve industrial electrification goals. Ultrasound irradiation has been employed as a powerful tool in biomass pretreatment and biorefining, as well as a green extraction method for recovering bioactive molecules. By partially degrading lignin structures, ultrasound irradiation significantly improves the biological conversion of waste materials and lignocellulose, facilitating the exposure of valuable macromolecules, i.e., cellulose and hemicelluloses. This research begins with an introduction to sonication technology, and subsequently presents comprehensive discussions focusing on the application of ultrasound in the pretreatment of sludge and lignocellulosic materials for anaerobic digestion. Furthermore, various facets of ultrasound usage in bioethanol production, including substrate pretreatment, enzymatic and acid hydrolyzes, and fermentation techniques, are also examined. Additionally, the benefits of employing ultrasound technology to recover high-value, heat-sensitive bioactive compounds at temperatures below their degrading points, thereby preserving their functionality, are explored. Looking ahead, this review explores current trends in ultrasound technology adoption and its potential for scaling up and commercialization, introducing pathways for a more sustainable and efficient approach for biomass valorization.