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厨余垃圾、绿化废弃物和茶叶渣中试共堆肥系统效果评估

Evaluating co-composting of kitchens, greening wastes, and exhausted tea on a pilot scale

  • 摘要: 为解决厨余垃圾等有机废弃物处理难的问题,该研究以厨余垃圾、绿化废弃物和茶叶渣为主要原料,通过控制通风方式和菌种类型在堆肥成套设备内开展中试好氧堆肥,选取温度、含水率、碳氮比(C/N)、总养分、有机质含量、种子发芽指数和卫生学特性等指标评估共堆肥系统的技术可行性和经济可行性。结果表明:选择间歇式通风方式并按质量分数1‰投加复配菌剂,堆肥在65 ℃以上高温持续7 d;经10 d发酵,物料含水率和C/N分别从63.5%和31.5降至30.1%和9.6;堆肥产物的总养分(9.8%,质量分数,下同)和有机质含量(43%)均远高于NY/T 525-2021农业行业标准(总养分≥4%,有机质含量≥30%);堆肥产物腐熟度和卫生学特性状况良好,种子发芽指数达88.3%,粪大肠菌群数<3 个/g,产物中未发现蛔虫卵。该共堆肥系统的废物平均处置成本低至(248.67±19.89)元/t。研究结果可为实现厨余垃圾、绿化废弃物和茶叶渣的低成本、规模化处理,有效解决厨余等有机废弃物环境污染问题提供参考依据。

     

    Abstract: Abstract: Effective disposal of organic wastes has been one of the most important issues for the resource utilization of solid wastes. The degradation rate of organic components as a key factor can pose a serious impact on the composting process. In this study, a series of experiments were performed on the microbial agents and various ventilation systems, in order to evaluate the co-composting performance of kitchens, green wastes, and exhausted tea on a pilot scale. An optimal compound ratio was also achieved to verify the strengthening effect of co-composting. The specific organic components included the fat crude, fibers, and protein in the mixed ingredients during composting. Specifically, kitchen waste, green waste, and exhausted tea were selected as the main raw materials. An aerobic composting was then carried out to control the ventilation and the type of microbial agents in a pilot composting plant. Some parameters were selected to fully evaluate the technical feasibility and economic viability of the co-composting system, including the temperature, water content, the carbon to nitrogen ratio, total nutrients, organic matter content, seed germination index, and hygienic characteristics. The results showed that the optimal combination was the self-developed microbial agents under the intermittent ventilation pattern, where the ratio of compound agents for the co-composting was that m(Aspergillus oryzae): m(Bacillus licheniformis): m(Candida lipolytica): m(Trichoderma viride): m(Azotobacter chroococcum) = 1.5:1:1.2:2:1. Meanwhile, the microbial agents presented a stronger removal effect of the specific organic component in the mixed ingredients, when the inoculation amount was 1‰. Three classic phases were obtained in the temperature of the mixed ingredients during 10 days of drum composting, including heating, thermophilic, and cooling phases. Furthermore, the maximum temperature was up to 68.6℃, while the high-temperature period (65℃ or higher) remained for 7 days. The ratio of water content and carbon to nitrogen declined from 63.5% to 30.1%, and 31.5 to 9.6, respectively, during the entire composting. The total nutrient (9.8%) and organic content (43%) were superior to the Agricultural Industry Standard NY 525-2021. Meanwhile, the seed germination index of the composting product reached up to 88.3%, indicating the perfect hygienic characteristics of composting (3 or fewer fecal coliforms per grams, no ova of roundworm was found). For economic feasibility, the co-composting system was applied for the domestic waste treatment in a district with a population of 30 000 in the Hengqin area of Zhuhai, Guangdong Province, China. A systematic analysis was made to consider the revenues (including waste disposal, organic fertilizer products, and scrap recycling revenue) and expenses (including utilities, salary, transportation, landfill disposal, venue rental, machinery and equipment depreciation, and unforeseeable expenses) during practical application. The average disposal cost was required as low as (248.67±19.89) yuan/t. As such, a process control strategy can be recommended to recycle the kitchen wastes, green wastes, and exhausted tea in the ecosystem, instead of being discarded as solid wastes. The short processing time can be widely expected to accelerate the degradation rate of organic matters for better compost quality during resource utilization. Meanwhile, an improved process control system can be used for the organic waste composting in a rotary drum reactor. The finding can provide a strong reference to effectively treat the environmental pollution of organic wastes in the large-scale kitchen waste, green waste, and exhausted tea at low cost. The recycling of organic waste resources can greatly contribute to reducing landfill disposal for less environmental pollution.

     

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