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As the worldwide demand for green energy intensifies, the generation of biogas through the anaerobic digestion (AD) process serves as a potential and promising sustainable solution. It also addresses the problem of solid waste management through the biodegradation of solid organic waste. Despite its huge potential, the conventional AD process often encounters significant operational challenges, such as the complexity of feedstock characteristics and structures, which make the breakdown process ineffective and inefficient in biodegradability. Such issues collectively contribute to reduced biogas yields, limiting the efficiency of the AD process and the viability of biogas as a reliable energy source. To address these obstacles, process intensification of the feedstock emerges as a necessary strategy. This paper presents a review of primary pretreatment methods and hybrid methods that have been developed to optimize the AD process. The affecting parameters of the conventional pretreatment techniques, along with the working principle, methodology, and their limitations, are discussed. Hybrid methods combine multiple pretreatment methods for maximum effectiveness and overcome the limitations of individual techniques. Chemo-sonication and mecho-sonication have achieved increases in biogas generation ranging from 67 % to nearly 94 % compared to untreated feedstock. The review concludes with a comparative analysis of these pretreatment techniques, which provides valuable insights into the relative productivity of each technique. This study proposes a framework of future research to optimize the AD process in a more efficient way and as well as yielding a stable generation of methane. This paper offers a clear pathway to enhancing biogas production, contributing to the broader goal of renewable, sustainable, and green energy development.
Shah et al. (Tue,) studied this question.