Sewage Sludge Pretreatment for Enhanced Biogas Production
Abstract
The growing demand for renewable energy and the environmental challenges posed by sewage sludge management have intensified interest in biogas production through anaerobic digestion. However, the complex and recalcitrant composition of sewage sludge-rich in macromolecular compounds such as proteins, lipids, cellulose, and extracellular polymeric substances-limits its biodegradability and methane yield. Pretreatment technologies have emerged as essential strategies to overcome these challenges by enhancing the hydrolysis phase, the rate-limiting step in anaerobic digestion. This review comprehensively examines the current status and effectiveness of thermal, mechanical, chemical, and biological pretreatment methods for sewage sludge. Thermal and mechanical approaches demonstrate the most significant improvements in methane production, with thermal methods achieving yield increases of up to 1000%, albeit with higher energy requirements. Chemical pretreatment offers moderate enhancements but raises environmental concerns, while biological methods are eco-friendly yet less effective when applied alone. The selection of an appropriate pretreatment strategy depends on factors such as sludge characteristics, operational costs, technological infrastructure, and environmental sustainability. As global wastewater generation continues to rise, optimizing pretreatment technologies is crucial for maximizing biogas output and advancing sustainable sewage sludge management. This review highlights the advantages, limitations, and future prospects of various pretreatment methods, providing guidance for the development of efficient and environmentally responsible biogas production systems.
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