Aerobic fermentation equipment for kitchen wastes in rural courtyard

Aerobic composting is one of the primary steps for the resource utilization and harmless treatment of rural kitchen waste. The treatment device of food waste is ever increasingly needed for single or multiple households, as the development of separate waste collection and promotion of on-the-spot organic waste disposal and utilization. In this study, an aerobic composting device was designed to consider segmented fermentation for composting material, precise aeration and turning control, and multi-function integration. According to the four-stage aerobic composting, four chambers of sequential fermentation were utilized to achieve the separate fermentation of materials in different stages for the harmless treatment of the product. This integrated system also incorporated the agitation apparatus, aeration equipment, control devices, leachate collection mechanisms, and odor control systems. Continuous feeding was employed to introduce the kitchen waste and sawdust daily at a wet-to-weight 10:3. The aeration strategy was set at one minute of aeration every 10 min, and an aeration rate of 10L/min. The stirring frequency was positive for 4 min, reverse for 6 min, and stop for 240 min. The mixing performance simulation and composting experiment were conducted using kitchen waste and pine sawdust as the feedstock. In the simulation test: a fermentation tank and material particle model were constructed and calibrated the simulation parameters of kitchen waste and pine sawdust. The mixing state was simulated to explore the effect of kitchen waste and pine sawdust in four fermentation tanks using the discrete element simulation software EDEM. The mixing degree was calculated for the two kinds of materials in the fermentation tank using the coefficient of variation. The working performance of the equipment was verified in the test. In the composting experiment, solid samples were collected on days 21, 23, and 25 of the composting process, termed as the feeding port (P1), discharge port (P6), and the mid-sections of the first to fourth fermentation tanks (P2 to P5). Physical and chemical properties were determined for the maturity indices of the fermented products. The gas samples were analyzed using portable gas detectors to measure the concentrations of ammonia (NH₃) and hydrogen sulfide (H₂S) within the first, second, third, and fourth fermentation chambers, as well as at the outlet of the deodorization unit (P7). The results show that the mixing uniformity of materials in the fermentation bin was about 94%, which fully met the requirement that the mixing degree of fermentation materials reached 90%. Furthermore, the color of the fermented material was gradually darkened, the unpleasant odor gradually dissipated, and the fermented material was loose and granular after aerobic fermentation. The compost experienced a high-temperature phase exceeding 55 °C reached 5 d, and following 20 d of continuous fermentation. The number of fecal coliforms reached the hygienic safety standard. And egg mortality rate reached 100% for Ascaris lumbricoides. The seed germination index was 73%, fully meeting the requirements of the National Standard for Organic Fertilizer (NY/T 525-2021). In summary, continuous composting and independent fermentation control can be expected to effectively enhance the quality of the fermentation product in different stages. This research can also provide technical references for local resource utilization, fertilizer application, and harmless disposal of kitchen waste in rural regions.