Effect of different organic wastes on kitchen waste machine composting secondary fermentation

Five organic wastes were mixed with the kitchen waste machine compost to improve its key physicochemical properties, including garden waste, straw, wood chips, reeds, and rice hulls, and then subjected to a 35-day secondary fermentation, with an equal amount of kitchen waste compost mixed in as a control. The test results revealed that during the secondary fermentation process, all treatments experienced significant temperature increases, with the rice husk treatment experiencing significantly higher temperatures than the other treatments during the high temperature period. During the secondary fermentation process, the total nitrogen content of the composts decreased significantly, while the total phosphorus and potassium contents increased. In terms of water content, organic matter content, and pH indexes, all treatments met the requirements of the agricultural industry standard NY/T525-2021 Organic Fertilizers. All treatments showed good degradation rates for fats and oils in the kitchen waste machine compost, with straw and rice hulls showing the greatest degradation rates for fats and oils, both with a reduction in crude fat content of more than 60%. The composts made from wood chips and rice hulls had the lowest sulphur content, both less than 0.25%. The germination index of the reed, wood chip, and rice hull treatments met the requirements of the agricultural industry standard NY/T525-2021 Organic Manure. The rice husk treatment had the highest GI value (85.27%), while the garden waste treatment did not. In summary, this study conducted a secondary fermentation of kitchen waste machine compost and concluded that secondary fermentation with rice husk mixed with kitchen waste machine compost could have the most obvious effect on its properties such as decomposition, but the 35-d fermentation cycle made complete decomposition of kitchen waste machine compost difficult, and further research on the use of long-cycle fermentation to improve composting is recommended. More research on the use of long cycle fermentation to improve the properties of machine composted kitchen waste is suggested based on the findings of this study.