Flexible Biogas Technology: Design Strategies, Operational Challenges, and Pathways Ahead

Author(s): Gupta S, Chavan PP, Mohod AG, Aware SV and Rajemahadik VA

Abstract:

Anaerobic digestion is an established technology for converting biodegradable organic wastes into renewable biogas and nutrient-rich digestate. Flexible biogas plants have emerged as an alternative to conventional fixed-dome and floating-drum digesters, particularly for decentralized and rural applications, because of their simplified construction, reduced permanent infrastructure requirements, portability and adaptability. However, the performance and long-term applicability of flexible systems depend on feedstock characteristics, digester configuration and operating conditions. This review critically examines the development and current status of flexible biogas plants, covering their construction, components, working principle, configurations and major advantages and limitations. The review also discusses the suitability of different organic feedstocks, co-digestion strategies and the stages of anaerobic digestion, followed by an assessment of key operating parameters including temperature, pH, total solids, volatile solids, organic loading rate, hydraulic retention time, mixing and feeding conditions. Performance is evaluated using biogas production, specific gas yield, methane content, seasonal response and operational reliability. Economic aspects, including investment and operating costs, energy substitution, digestate utilization and financial indicators, are also considered. The environmental significance of flexible systems is discussed in relation to organic waste management, methane recovery, renewable energy production and nutrient recycling. Major challenges include membrane durability, leakage, temperature sensitivity, gas-pressure management, feedstock availability and limited technical support. The review identifies key research needs in long-term durability, seasonal performance, capacity-based comparison, standardized performance evaluation, economic assessment, digestate utilization and low-cost monitoring. Future development should focus on durable materials, improved system reliability, simple monitoring and adaptable decentralized configurations. Overall, flexible biogas plants show considerable potential for integrated organic waste management, renewable energy generation and nutrient recovery, provided that long-term technical and operational limitations are adequately addressed.

keywords:
Anaerobic digestion; Biogas; Flexible biogas plants; Flexible digesters; Organic waste; Biogas performance; Digestate; Renewable energy

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