Comprehensive thermal assessment of anaerobic digestion process in biogas plants

Abstract

As the world transitions toward renewable energy solutions, anaerobic digestion (AD) is emerging as a key technology for biogas production. Among the key parameters influencing biogas production, temperature plays a critical role. Without adequate thermal regulation, biogas production may drop by over 50 %, impacting plant feasibility. This review comprehensively analyses thermal management in AD, emphasizing the critical role of temperature regulation and the factors affecting thermal demand. A structured three-tiered approach that incorporates heat retention, recovery, and external supply is presented to optimize thermal efficiency and reduce operational costs. Passive techniques utilizing insulation and phase change materials can reduce heat loss by up to 82 % and lag internal temperature fluctuations. Waste heat recovery from effluent, equipment, and/or integrated industry can meet up to 100 % of thermal energy requirements. Although solar thermal systems are observed to offer low-emission and operating-cost heating, their high capital and land requirements may limit feasibility. Hybrid systems combining solar, biogas, and biomass can provide scalable, climate-resilient alternatives with lower emissions and improved reliability. The review also dwells into Techno-economic evaluations showing that, despite capital and operating costs, well-designed systems achieve net-positive energy outcomes and short payback periods. Chronological advancements in computational fluid dynamics and modelling demonstrate prediction accuracy exceeding 85 %, significantly reducing design uncertainties and implementation costs. This review concludes with challenges and recommendations for modular, strategic, site-specific hybrid heating strategies, future policy, and research suggestions. By integrating technical insights, it offers a comprehensive framework to enhance AD performance, energy efficiency, and environmental sustainability.