Techniques for Enhancing Anaerobic Digestibility of Municipal Solid Waste

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The goals of wastewater treatment are currently changing from public sanitation and environmental protection towards nutrient and energy recovery, which are driven by the high cost of energy and value in nutrients. Energy from municipal solid waste is considered to be one of the most promising future renewable energy sources. Anaerobic digestion (AD) is the default process for the biological conversion of organic waste to renewable energy and biofuel. AD is a multi-steps process in which the complex organic compounds are converted to the most oxidized and reduced form such as mono-atomic carbon dioxide and methane. In recent years, the application of AD for the treatment of organic waste has emerged dramatically. The attractiveness of AD is due to the various benefits of the process: (a) the produced biogas is energy efficient and environmentally friendly, (b) the produced slurry (digestate) is nitrogen rich and can be utilized in agriculture as a nutrient fertilizer and/or organic amendment, (c) a more recent application is to transform the digestate into biochar, which can be further employed as soil enhancer or an adsorbent for the purification of wastewater or flue gas. The major drawbacks of AD are its long retention time (typical 20-30 days) and the low overall degradation efficiency of organic matter, which is partly caused by the inability of the anaerobic microorganisms to degrade certain organic compounds efficiently. In spite of all the efforts in the AD of municipal solid waste sector, the process is not yet fully understood, and further development and optimization of the current technology, especially in the above-mentioned areas, is still needed.