# Impact of Particle Size on the Aerobic Decomposition and Fertilizer Efficiency of Corn Cobs: A Sustainable Waste-to-Resource Approach

## TL;DR

This study shows that grinding corn cobs to a medium size improves composting efficiency and produces better fertilizer, helping turn agricultural waste into a valuable resource.

## Contribution

The study identifies 10-mesh particle size as optimal for corn cob composting, enhancing humification and microbial activity.

## Key findings

- 10-mesh corn cobs achieved the highest humification and compost maturity with a germination index of 93.63%.
- Medium-sized particles supported a more diverse and effective microbial community for decomposition.
- Particle size was found to strongly influence composting outcomes through microbial community modulation.

## Abstract

Corn cobs are abundant agricultural residues that can be recycled into compost to improve soil fertility and support sustainable farming. However, their fibrous structure makes them slow to break down, and efficient composting depends on optimizing processing conditions. This study examined how different corn-cob particle sizes affect aerobic composting performance. We found that particle size strongly influenced temperature evolution, organic-matter degradation, nutrient retention, and humification. Medium-sized particles offered the best balance between aeration and moisture, promoting active microbial metabolism, faster decomposition, and higher compost maturity compared with finer or coarser particles. These results show that selecting an appropriate particle size can significantly improve composting efficiency and compost quality when recycling corn residues. This strategy provides a practical and sustainable pathway to convert crop waste into nutrient-rich fertilizer, reduce dependence on synthetic inputs, and enhance soil health in agricultural systems.

The conversion of agricultural residues into high-value organic amendments is fundamental to sustainable farming systems. Corn cobs represent a widely available lignocellulosic resource; however, their rigid structural properties often hinder efficient biodegradation during composting. This study evaluated whether optimizing corn cob particle size could improve aerobic composting performance by enhancing humification and compost quality. Corn cobs were ground into three particle sizes (6-mesh, 10-mesh, and 20-mesh) and composted with a commercial microbial inoculant for up to 51 days. Physicochemical properties, humic substance fractions (HSC, HAC, FAC), microbial community dynamics (16S rRNA and ITS sequencing), and maturity indicators were monitored. The 10-mesh treatment (M10) exhibited the most favorable composting outcomes, achieving the greatest degree of humification (HA/FA = 2.85; HAC = 48.30 g/kg) and the most pronounced aromatic condensation in humic acids. M10 also supported a more diverse and metabolically specialized microbial consortium, with notable enrichment of lignocellulose-degrading and humus-forming genera (e.g., Streptomyces, Thermobifida). Consequently, M10 produced the most mature compost, reflected by the highest germination index (93.63%) and the lowest heavy-metal accumulation, meeting agricultural safety standards. Structural equation modeling revealed that particle size influenced humification primarily by modulating microbial community structure (path coefficient = 0.86), highlighting particle size as a key environmental selector in composting systems. Overall, 10-mesh particle size created an optimal aeration–moisture balance that stimulated microbial metabolism, accelerated organic matter degradation, and enhanced stable organic matter formation. These findings demonstrate that corn cob particle size significantly governs composting efficiency and final product quality. Selecting a 10-mesh size presents a practical pretreatment strategy to accelerate biomass turnover and produce safe, nutrient-rich compost, providing an effective approach for sustainable bioconversion of agricultural residues.