Abstract
Anaerobic digestion (AD) is a vital technology for sustainable waste management and renewable energy production, converting organic waste into methane-rich biogas and nutrient-rich digestate. Despite its potential, AD faces barriers to large-scale adoption, including feedstock variability, process instability, and high operational costs. This review critically evaluates recent advancements in AD technology, focusing on innovations that enhance efficiency and scalability, while identifying key challenges and policy gaps—particularly in developing economies. A systematic literature review (2014–2024) was conducted using PRISMA guidelines, analyzing 210 peer-reviewed studies from Scopus, Web of Science, and ScienceDirect. Quantitative and thematic analyses were performed using NVivo and VOSviewer. Recent advancements demonstrate that pretreatment strategies (e.g., enzymatic hydrolysis, thermal methods) improve biogas yields by 20–360%, while microbial bioaugmentation enhances process stability. Hybrid systems, such as temperature-phased AD, achieve 29% higher methane yields than conventional reactors, though economic viability remains dependent on policy support (e.g., the EU’s RED II incentives) and AI-driven optimization. Challenges persist in low-income regions due to high capital costs and infrastructural limitations. Future Directions: Integrating circular economy principles, hybrid renewable energy systems (e.g., AD-solar), and decentralized models can address scalability challenges. This review uniquely bridges lab-scale innovations with actionable policy insights, emphasizing AD’s role in global energy transitions.

Key words: Biogas generation, anaerobic digestion, renewable energy, feedstock enhancement, circular economy, microbial communitiesAlgeria.