Biogas production through anaerobic digestion (AD) is an important renewable-energy pathway that supports organic-waste management, resource recovery, and decarbonization of energy systems. However, its performance varies with feedstock characteristics, process conditions, technology configuration, infrastructure, and local economic and policy conditions. This review critically synthesizes advances in biogas production technologies, emphasizing feedstock utilization, process optimization, anaerobic digestion configurations, biogas upgrading, sustainable energy applications, environmental performance, techno-economic feasibility, and emerging technological pathways. A structured literature search was conducted using Scopus, Web of Science, and Google Scholar, resulting in a final evidence base of 174 references selected through predefined eligibility and data-extraction criteria. The review shows that co-digestion, pretreatment, temperature-phased digestion, reactor optimization, and advanced process monitoring can improve methane production and operational stability, although reported performance is strongly dependent on feedstock composition and experimental conditions. The analysis further demonstrates that methane leakage, digestate management, energy requirements, and system boundaries can substantially influence the environmental benefits of AD. Economic viability is similarly context-dependent, being affected by plant scale, feedstock logistics, financing conditions, energy markets, infrastructure, and policy support. Advanced upgrading, digital monitoring, hydrogen-assisted methanation, nutrient recovery, biochar-assisted digestion, and bioelectrochemical approaches offer further opportunities, but their technological readiness and commercialization prospects differ considerably. The review identifies persistent gaps in scale-up validation, methane-loss measurement, standardized techno-economic and life-cycle assessment, feedstock variability, and deployment in developing regions. Future progress will depend on integrated systems that combine reliable methane production with methane-loss minimization, resource recovery, digital process control, economic viability, and verified life-cycle environmental performance.