Raw material pretreatment is a foundational stage in organic fertilizer production; it directly determines the efficiency of subsequent fermentation and the quality of the finished product. Its core objective is to transform raw organic materials into qualified substrates suitable for fermentation through the coordinated application of various equipment, auxiliary materials, and processing techniques. This process necessitates the use of specialized machinery, conditioning additives, and auxiliary tools—each being indispensable—working together to create optimal conditions for microbial fermentation.
The most critical component of pretreatment is specialized equipment, primarily comprising crushing machinery, solid-liquid separation systems, and mixing and batching equipment. Crushing equipment—typically hammer mills or half-wet material crushers—is used to pulverize coarse-fiber raw materials, such as crop stalks and tree branches, into fragments ranging from 1 to 5 centimeters. This process increases the raw materials' surface area, thereby facilitating microbial attachment and decomposition. Solid-liquid separation equipment—such as screw-press separators—can process livestock and poultry manure with moisture levels between 70% and 80%, reducing the moisture content to a range of 60% to 65%. This step prevents the generation of foul odors and the formation of anaerobic environments during fermentation. Mixing and batching equipment—primarily horizontal twin-shaft mixers—is employed to ensure the uniform blending of manure, stalks, microbial inoculants, and other ingredients, thereby guaranteeing consistency in the material's physical and chemical properties.
Conditioning additives serve as a vital support mechanism during pretreatment, primarily utilized to optimize the characteristics of the raw materials. To adjust the carbon-to-nitrogen (C/N) ratio to the optimal range of 25–35:1, carbon-rich additives (such as crop stalks and rice husks) and nitrogen-rich additives (such as livestock and poultry manure) are required. For instance, if the C/N ratio of a specific raw material—such as chicken manure—is too low, pulverized crop stalks can be added to bring it into the desired range. Regarding moisture regulation, raw materials with high moisture content require the addition of dry absorbents (such as sawdust or rice bran), while low-moisture materials require the addition of clean water to maintain the moisture level within the optimal range of 50% to 60%. Furthermore, biological fermentation inoculants—such as *Bacillus subtilis*—may be added to accelerate the subsequent fermentation process.
Auxiliary tools and processing techniques are equally indispensable. Vibrating screens are used to remove impurities—such as plastics and metals—from the raw materials, thereby protecting downstream processing equipment and enhancing the quality of the finished fertilizer. In small-scale production settings, manual grates and conveyor belts are also utilized to facilitate the sorting and transfer of raw materials. Additionally, some large-scale production facilities employ high-temperature pretreatment processes; when combined with biochar, this method effectively reduces the levels of heavy metals and antibiotics present in the raw materials, thereby enhancing the safety of the final product. In summary, the pretreatment of raw materials requires the coordinated interplay of equipment, auxiliary materials, and tools. This entails utilizing specialized equipment to optimize the physical form of the raw materials, relying on auxiliary materials to regulate key parameters, and employing supplementary tools to ensure the smooth execution of the process. Only through the scientific integration of these essential elements can a solid foundation be established for the efficient fermentation of organic fertilizers and the enhancement of their quality, thereby driving the resource-oriented utilization of organic waste.
