EVALUATION OF DESIGN CHARACTERISTICS FOR ANIMAL MORTALITY COMPOSTING SYSTEMS

Composting is an aerobic process that relies on natural aeration to maintain proper oxygen levels. Air-filled porosity, mechanical strength, and permeability are among the essential parameters used to optimize the process. This study's objective was to measure the physical parameters and airflow characteristics of three commonly used cover materials at four moisture levels, which could be used in designing actively aerated swine mortality composting systems. A laboratory-scale experiment was conducted to measure pressure drops across the cover materials as a function of the airflow rate and the material's moisture content. Compressive stress was applied for 48 h to simulate the impact of swine mortalities on the cover materials. The power required to aerate each material was determined as a function of volumetric flow rate and moisture content. As expected, air-filled porosity and permeability decreased with increasing bulk density and moisture content. The highest average permeability values were measured at 25% moisture content and ranged from 66 x 10(-4) to 70 x 10(-4) mm(2), from 161 x 10(-4) to 209 x 10(-4) mm(2), and from 481 x 10(-4) to 586 x 10(-4) mm(2) for woodchips, ground cornstalks, and sawdust, respectively. For the range of airflow rates tested in this study (0.0025 to 0.0050 m(3) s(-1) m(-2)), a linear relationship (R-2 >= 0.975) was found between the volumetric flow rate (m(3) s(-1)) and the power required to aerate the compost pile (W per 100 kg of swine mortality).

Automated summary

This study aimed to measure the physical parameters and airflow characteristics of three commonly used cover materials at different moisture levels for designing actively aerated swine mortality composting systems. The results showed that air-filled porosity and permeability decreased with increasing bulk density and moisture content.