Experimental Study on Physical Properties of Co-composting Cow Manure and Walnut Branches and Load Calculation of Compost Turner

Abstract

To address the lack of physical property parameters during cow manure composting and the insufficient design basis for composting equipment, this study investigated the dynamic variation patterns of the physical properties of cow manure under different composting treatments and applied the measured parameters to the load calculation of the compost turner main shaft. [Methods] Three composting treatments were set up: pure cow manure, cow manure + walnut branches, and cow manure + walnut branches + microbial agent. Referring to soil mechanics test methods, the changes in moisture content, hardness, shear strength, cohesion, and the tangent of the internal friction angle during the composting process were measured. The measured strength data were then used to calculate the maximum torque on the compost turner main shaft. [Results] The study showed that the cohesion and the tangent of the internal friction angle of the compost were negatively correlated with moisture content. In the later stage of composting (moisture content 28.4%), the cohesion reached 38.412 kPa, and the tangent of the internal friction angle was 0.2982. Adding walnut branches improved the compost structure, and adding the microbial agent made the compost looser and reduced compaction. Based on the most unfavorable working condition (all mixing rods buried in the compost with one row perpendicular to the ground), the calculated maximum torque on the compost turner main shaft was 7.28 kN·m. [Conclusion] This study provides reliable basic data for the structural design and power selection of compost turners, offering guidance for the optimization of equipment for the resource utilization of livestock and poultry manure.