Composting has emerged as a suitable method to convert or transform organic waste including manure, green waste, and food waste into valuable products with several advantages, such as high efficiency, cost feasibility, and being environmentally friendly. However, volatile organic compounds (VOCs), mainly malodorous gases, are the major concern and challenges to overcome in facilitating composting. Ammonia (NH) and volatile sulfur compounds (VSCs), including hydrogen sulfide (HS), and methyl mercaptan (CHS), primarily contributed to the malodorous gases emission during the entire composting process due to their low olfactory threshold. These compounds are mainly emitted at the thermophilic phase, accounting for over 70% of total gas emissions during the whole process, whereas methane (CH) and nitrous oxide (NO) are commonly detected during the mesophilic and cooling phases. Therefore, the human health risk assessment of malodorous gases using various indexes such as ECi (maximum exposure concentration for an individual volatile compound EC), HR (non-carcinogenic risk), and CR (carcinogenic risk) has been evaluated and discussed. Also, several strategies such as maintaining optimal operating conditions, and adding bulking agents and additives (e.g., biochar and zeolite) to reduce malodorous emissions have been pointed out and highlighted. Biochar has specific adsorption properties such as high surface area and high porosity and contains various functional groups that can adsorb up to 60%–70% of malodorous gases emitted from composting. Notably, biofiltration emerged as a resilient and cost-effective technique, achieving up to 90% reduction in malodorous gases at the end-of-pipe. This study offers a comprehensive insight into the characterization of malodorous emissions during composting. Additionally, it emphasizes the need to address these issues on a larger scale and provides a promising outlook for future research.

中文翻译：

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对堆肥过程中恶臭气体排放的表征、人类健康风险评估和缓解的严格审查


堆肥已成为一种将有机废物（包括粪便、绿色废物和食物垃圾）转化或转化为有价值产品的合适方法，具有效率高、成本可行和环境友好等优点。然而，挥发性有机化合物（VOC），主要是恶臭气体，是促进堆肥过程中需要克服的主要问题和挑战。氨（NH）和挥发性硫化合物（VSC），包括硫化氢（HS）和甲硫醇（CHS），由于其嗅觉阈值较低，是整个堆肥过程中恶臭气体排放的主要原因。这些化合物主要在高温阶段排放，占整个过程气体排放总量的70%以上，而甲烷（CH）和一氧化二氮（NO）通常在中温和冷却阶段检测到。因此，利用ECi（单个挥发性化合物的最大暴露浓度EC）、HR（非致癌风险）、CR（致癌风险）等多种指标对恶臭气体的人体健康风险进行了评估和讨论。此外，还指出并强调了一些策略，例如保持最佳操作条件以及添加填充剂和添加剂（例如生物炭和沸石）以减少恶臭排放。生物炭具有高比表面积、高孔隙率等特定吸附特性，含有多种官能团，可吸附堆肥过程中排放的恶臭气体高达60%~70%。值得注意的是，生物过滤成为一种有弹性且经济高效的技术，可将管道末端的恶臭气体减少高达 90%。 这项研究提供了对堆肥过程中恶臭排放特征的全面见解。此外，它强调需要在更大范围内解决这些问题，并为未来的研究提供了有希望的前景。