The increasing production of sewage sludge (SS) from wastewater treatment plants presents significant environmental challenges worldwide, requiring sustainable treatment strategies that enable resource recovery while minimizing environmental risks. Although composting is widely recognized as an effective method for SS stabilization, current technologies still exhibit limitations, including inefficient oxygen transfer, uneven aeration, high greenhouse gas emissions, and insufficient control of emerging contaminants. This review aims to synthesize current knowledge on SS composting with a focus on strategies for improving operation performance and reducing environmental impacts. Recent studies indicate that composting performance is strongly influenced by factors such as temperature, moisture content, aeration, carbon-to-nitrogen (C:N) ratio, and the use of suitable bulking agents. In addition to conventional approaches, alternative technologies—including co-composting, in-vessel systems, vermicomposting, and pretreatment methods—are discussed as pathways for improving system efficiency. Special attention is given to emerging innovations such as nanobubble aeration, which shows potential to enhance oxygen transfer and reduce anaerobic zones, although its application in composting remains insufficiently explored. The review highlights critical knowledge gaps related to aeration optimization, contaminant behaviour, and process integration, identifying opportunities where further scientific research can significantly advance SS composting toward more efficient and environmentally sustainable systems.
Ivickytė et al. (Mon,) studied this question.
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